Wireless World 1986 11

THE
JOURNAL
FOR
PROFESSIONAL
ENGINEERS
ELECTROMCS
& WIRELESS
[NOVEMBER 1986
SW
in the
ionosphere
11 years
Turing's
computable
numbers
Mobile radio
survey
Programmable
logic and the
68020
BBC television
looks backand forward

High
performance
video digitizer
1.95
THE U.K.'s
[1411
TEST EQUIPMENT
DISTRIBUTION COMPANY
MARCONI
INSTRUMENTS
LARGE SAVINGS ON
PHILIPS COUNTER/TIMERS
2955 Radio Communications
UNTIL 31st
31st OC'l'OBER
OCTOBER
IYB
1986
Test Set
11 test functions, including full
duplex radio test
38 instrument settings in nonvolatile memory
Revolutionary design:
fast and easy to use
5750
2022 AM/FM Signal Generator
2440 Microwave Counter
Wide frequency coverage:10 Hz to 20 GHz
Fast acquisition time: only 200 ms typical
High -stability oven controlled crystal oscillator
3650
Wide frequency coverage:10 KHz to

1000 MHz
Simple push button operation, large LCD
display.
Comprehensive
modulation: AM/FM/PhM
2382/80 Spectrum Analyser
and Display, 100Hz-400MHz
2950
18950
Exceptionally fast auto -tuning, with low
noise
True RMS Voltmeter to 25 MHz
2
1200
Modulation analysis, including frequency and power
5392 2019A AM/FM Signal
Generator to 1040 MHz
4530
2018A AM/FM Signal
Generator to 520 MHz
4300
2305 Modulation Meter
50 kHz to 2.3 GHz frequency range
HAMEG
OSCILLOSCOPES
Digital Storage
Oscilloscope
HM 205
PM6670/01 High resolution

counter/timer, to 120MHz,590
10mV sensitivity
PM 6671/01 Enhanced features
unit, to 120MHz, with
trigger level output
660
PM 6672/01 Higher frequency
meter, to 1GHz,
10ps resolution
PM 3055 50MHz Dual Time
Base Oscilloscope
auto -set for amplitude, timebase
and triggering
Multi -function menu driven soft keys
LCD panel displays settings and
status
CRT 16kV acceleration
voltage
HM 203-6 20 MHz
HM 204-2 20 MHz
Multifunction Oscilloscope
variable readout speeds
HM 208 Digital Storage

scope with IEEE
1300
HM 605 60 MHz
843
0.1% resolution
Scanning and recording capability
Standard Oscilloscope
IEEE interface fitted as standard

digit to 61/2 digit modes
Up to 100 measurements/second
Accuracy to 0.005%,
resolution to 100nV
31/2
JF 37 Bench Portable OMM

31/2 digit LCD with analogue
bar graph
Auto/manual ranging
0.1% basic DC accuracy
Touch -hold facility
187
JF 52 Dual Point Digital
Thermometer
Active video trigger for

stable TV triggering 448
Real time or digital storage to 20 MHz

Low frequency event storage max
sensitivity 1 mV
Special background memory useable with
main memory
Chart plotter output at
PM 2534 Complete System

True RMS Multimeter
FLUKE DIGITAL
MULTIMETERS
Real time to 20 MHz, storage

to 100KHz
Resolution of 1024 x 256
points on X and Y axes
Single and re -fresh modes
HM 208 Digital Storage Oscilloscope
845
JF 27 Ruggedized Hand -Held DMM
Oscilloscope
Dual trace and sweep delay

Maximum sensitivity 1mV
In-built component tester

Z modulation and
X-Y operation
Min/max storage
Touch -hold facility
3 /2 digit LCD with Bar graph
JF 51 Single Point Digital
Nin/Max and relative mode operation

Touch -hold facility and auto
ranging
DC accuracy 0.1%
Thermometer
JF 25 Sealed and
ruggedized hand-held DMM
1550
77 Multifunction Hand -Held
216
DMM
JF
193
digital meter
JF 75 Full -feature analogue/
JF 73 Hand -Held DMM with

simplicity and value
133
95
110
88
72
For the full stories, also latest news on

Grundig, Thandar and Thurlby, contact:
,
170
o
0
Electronic Brokers
140/146 Camden Street, London NW1 9PB

Tel: 01-267 7070. Telex: 298694. Fax: 01-267 7363
CIRCLE.74 FOR FURTHER llETA1Ll;
www.americanradiohistory.com
NOVEMBER 1986
VOLUME 92 NUMBER 1609
IMIWIRIRMAZWMOMONAUTMfflatellIM
ELECTRON ICS
&
WIRELESS WORLD
LOGS AGAIN
BBC DATACAST
33
95
After ringing the bels in October, JW is now

hacking away at logs.
by Joules Watt
In a similar process to that used in teletex,

independent data lines are transmitted for
closed user -groups.
by J.P. Chambers
ACTIVE COMPENSATION
OF OP -AMPS
Front cover is a solar prominence,

illustrating the article on solar activity on
page 23. Picture from Science Photo
Library.
FEATURES
49
107
This general method of simulating non inverting v.c.v.s. building blocks reveals
several new structures.
by A. Soliman
Second -user test equipment is often

purchased by large companies. This article
explains the reasons.
by Peter Fraiman and David Price
FIFTY YEARS OF
COMPUTER SCIENCE
52
An appraisal of A.M. Turing's paper 'On
computable numbers', published in 1936.
by Tom Ivall
MOBILE RADIO'S MANY

OPTIONS
BROADCAST RADIO DATA
63
Mobile radio is one of the largest growth

areas in communication.
by Mark Nelson
Both IBA and BBC begin RDS next year.

This article describes Radio data on v.h.f.
and I.f.
by D.T. Wright and S.M. Edwardson
WIDE AREA BINARY
PROGRAMMABLE LOGIC
PAGING
DESIGN
65
12
Radio paging is an effective, low-cost
alternative to telephones.
by J.C. Kirby
BBC TELEVISION LOOKS

BACK AND FORWARD
17
On the fiftieth anniversary of broadcast
high -definition television, Pat Leggatt

reviews progress.
by D.P. Leggatt
ELEVEN YEARS IN THE
IONOSPHERE
23
complete sunspot cycle investigated by
ionosonde with results plotted graphically.
by Kurt Feldmesser
A
HEAT SINK SIMULATION
30
Take a cool look at your next heat -sinking
problem with this versatile technique.
by J.M. Howells
NEW OR USED?
COMMENT
3
Late extras
CIRCUIT IDEAS
32
Sine waves with fast amplitude stabilization
Speech chip control
RESEARCH NOTES
41
FEEDBACK
43
Using 68020 bus -size decoding as an

example, Chris Jay describes the use of a
programmable -logic i.c.
by Chris Jay
APPLICATIONS
STE BUS
72
Hall -effect i.cs

Audio delay devices
Standard Eurocard bus - STE - is for small to -medium complexity systems.

by Anthony Winter
VIDEO FRAME STORE
76
This versatile unit will capture, display and
process video images. This article is the first
in a series on image processing and
analysis.
by D.E.A. Clarke
CHARGE -COUPLED
DEVICE TECHNOLOGY
93
Extensive development of charge -coupled
pick-up devices has led to a highperformance camera.
by K. Shinoda and E. Tamura
58
NEWS AND DIARY
60
Euro information exchange
Awards for young designers
PRODUCTS
81, 83, 85, 87, 89

COMMUNICATIONS
COMMENTARY
98,101,103
BOOKS
105
WORKFILE
113
1
This is just aS
our huge inventory
OSCILLOSCOPES
SIGNAL SOURCES
Hewlett Packard
1500
1950
180 TR
100MHz Scope M/F (Mint)
1 71 5A opt 101
200MHzScope
Philips
PM3295
350MHz Scope
PM3540
Logic Anal/Scope
4455
1500
Tektronix
465B/0M44
4658
475A
475A/DM44
485
608
634 opt 1.20
2445
2465
5223
7104
7603
7704A
7834
R7603
7854
7904
2000
1450
1950
2500
4500
1500
750
2550
3450
3600
16000
1950
2850
7500
1950
10500
5500
100MHz Scope DM M
100MHzScope
200MHz Scope
200MHzScope/DMM
350MHz Scope
Monitor
Display Monitor
150MHzScope
300MHz Scope
Scope Mainframe (Mint)
1GHz Scope M/F
100MHzMainframe
200MHzMainframe
Fast Storage Scope M/F
100 MHz Rack MNTM/F
400MHzM/FScope
500 MHz Scope M/F
110(45710BU) 'The Portable'

150
Touchscreen
1506
Touchscreen
26318 opt 005. 017. 019 3rinter
2673A
Thermal Printer
69408
Multiprogrammer
7470A opt 001/002 A4 Plater
7475A opt 001/002 A3Plctter
7910H opt 015 Disk Drive
82913A
12 inchMcnitor
82937A
HPIB Interface
82938A
HPIL Interface
82939A
Serial Interface
82940A
OPIO Interface
B6B
Micrgconputer
9121D
Single -sited Disc Drive
98165
Personal Computer
Hewlett Packard
1150
4750
14500
5250
3500
Distortion Analyser P/In

Spectrum Analyser
Spectrum Analyser
Impedance Analyser
Spectrum Analyser P/In
Automatic Distortion Meter

110MHz SpectrumAnalyser
850
450
9650
Automatic Distortion Analyser

+ REC61 Plotter
1500
Wave Analyser
Radiometer
BKF 10
7ektranix
7L12
7L14
308
Spectrum Analyser P.
Spectrum Analyser P
Data Analyser
50MHz Pu se/Function Generator

5MHz Sweep Generator
Sweep Generator5MHz
1GHzSweeper
9862A
9915A
750
395
950
550
1650
1750
3950
3500
4500
950
995
1950
1500
1500
650
595
1750
HEWLETT PACKARD COMPUTERS
ANALYSERS
3580A
3585A
4193A
8557A
Marconi
TF 23304
TF 2337A
TF 2370
Hewlett Packard
Pulse Generator
214A
4204A
Digital Oscilator
80078
Pulse Generator
8011A
Pulse Generator20MHz
8018A-01
Serial Data Generator
8601A
Sweep Generator
8614A
Signal Generator
86260A
Sweep Ger. Plug-in 12.4-18GHz
864013001-002 AM/FM Signal Generator
86908
Sweeper Mainframe
Marconi
TF 20026
AM/FM Signal Generator
TF 2006
AM/FM Signal Generator 1GHz
Tektronix
SG 503
Signal Generator, 250MHz
Wavetek
166
184
185
1080
A large selection of 7000 series plug -ins available at up to

60% saving on list. Please call for quotations.
334A-01
Contact us with yourrequirement2,
1750
600
750
650
925
950
600
1250
1200
125
250
225
200
E350
1000
600
3500
6000
10500
1500
In
in
Plotter
Computer
GENERAL PURPOSE T & M
Farnell
SSG 520 + TTS 520 Transmission Test Set

Fluke
5200A/5215A AC Calibrator
7220A
Comms. Freq. Counter
G. P. Industrial
MFL 373
Fault Locator. MINT
Hewlett Packard
436A
Power Meter
467A
Amplifier
3403C
True RMS Voltmeter
34064
Sampling Voltmeter
3437A
High Speed D. V. M.
3465A
41Iz Digit D. M. M.
42718
Digital LCR Meter
50064
Signature Analyser
53006 + 53056 1300MHz Counter
5361A
80 MHz Counter
8447A
Amplifier
84470
Amplifier
Marconi
TF 1246
TF 13134
TF 2173
TF 2603
TF 2604
TF 2702
TF 2905/8
TF 2915
Tektronix
491
520A
P6015
1421
S1
RG 501
S. 3A
A6901
4041
PM 102
PM 107
PM 108
Oscillator
LCR Bridge 0.1 qb
Synchroniser for 2016

RF Millivoltmeter
Voltmeter
Inductor Analyser
TV Pulse Generator
Data Monitor
Spectrum Analyser
Vectorscope(NTSCI
H. V. Probe
Waveform Monitor
Sampling Head
Ramp Generator
Sampling Head
Isolation Monitor
System Controller
Personality Module
Personality Module
Personality Module
f
500
750
427
7500
350
395
1200
600
1850
1250
1250
350
2500
500
495
225
400
600
500
750
450
495
425
950
750
1200
7500
3750
400
1650
850
100
1250
E275
8800
500
675
650
ND NOW FOR OL.

-sST BROCHURE
il7DNIC IRVIs
1111E sou
All prices are exclusive of VAT and correct at time of going to press
u
III g
Hedelor Brolasrs
I '
0I
1g
[1
Carriage and packing charges extra
A copy of our trading conditions is available on
request
Electronic Brokers Ltd, 140-146 Camden Street, London NW1 9PB

Telephone:
01-267 7070 Telex: 298694 Fax: 01-267 7363
P
COMMENT
LATE EXTRAS
EDITOR
Philip Darrington
DEPUTY EDITOR
Geoffrey Shorter, B.Sc.
01-661 8 639
TECHNICAL EDITOR
Martin Eccles
01-6618638
PROJECTS EDITOR
Richard Lambley
01-6613039 or 8637 (lab.)

NEWS EDITOR
David Scbie
01-661 8632
DRAWING OFFICE MANAGER

Roger Goodman
01.6618690
ADVERTISEMENT MANAGER
Ashley Wallis
01-6613130
Michael Downing
01-6618640
CLASSIFIED EXECUTIVE
Susan Platts
01-6613033
ADVERTISING PRODUCTION
Brian Bannister
(Make-up and copy)
01.6618648
It is quite possible that the subject of AEW (Airborne Early Warning) is now so
emotive that rational discussion is difficult. Sums of money of the order of nearly a
billion pounds are unimaginable to most of us and simply register as rather a lot of
cash to pay for something which we have not yet got and which might not be what we
need anyway. Whether Weinstock'sWonder or the Grumman Gizmo or any of the other
bits of expensive ironmongery is chosen for the RAF, it has all gone on so long that the
original requirement itself is now suspect.
What the RAF wanted, all those years ago, was something to give warning of the
approach of hostile aircraft- large ones -so that they could go and intercept them. This
requirement can be met, even by the AEW Nimrod, albeit with some reported difficulty,
but military hardware has advanced in ingenuity in the last twelve years and bombers do
not drop things any more. What they do (or are intended to do should the occasion arise)
is to lurk about at a sensible distance and launch quite small cruise missiles.
Both u.h.f. and S -band radars are proposed for the RAF system, either of which in its
own way would be adequate for the task of detecting large aircraft more or less precisely,
depending on the radar beamwidth. But neither of them would find a cruise missile,
which is relatively minute with vestigial wings, amongst a lot of land and sea clutter.
Of course, the real question is-why try? What is a defending force going to do about a
swarm of tiny objects, each of which could devastate a city, if not several? Launch its own
swarm? The very same question could have been posed twelve years ago and received very
much the same answer, which is to the effect that the development has been a grotesque
mishandling of public resources, but that politics has made it necessary.
Almost any development carried out at the behest of the military exhibits all the
identifying characteristics of a lead balloon, so far as its capability of successful flotation is
concerned, at least in the UK. There are one or two notable exceptions, but experience
indicates that the military specifiers state what they would like to have if the world were
built out of sugar icing and marzipan, their wishful thinking becomes enshrined in a
Specification, the manufacturer takes it on without pointing out to the military that pie in
the sky is often tricky to design and can come expensive, and he is not tough enough to
.
discourage the military from thinking up simple -sounding but enormously expensive
modifications every other Thursday.
The result is inevitable: the development has gone on so long that it has already been
out of date for about eight years. Not much modern equipment is built from
twelve -year -old designs, using even older components. It would have been more sensible
to give the 900 million to the Soviets as Danegeld.
Or, perhaps, we could have used the money for something a little more rewarding, like
education, the health service or the rebuilding of industry.
NEW-STYLE EWW
promised last month, here is the new Electronics and Wireless World. The editorial
slanted rather more than in the past towards the working engineer who forms the
majority (over 80%) of our readership. Many of the suggestions that came out of our
recent survey have been incorporated, and we are confident that you will like the result.
The offer of a year's subscription for 11.70 remains open until the end of November:
take advantage now and save 6.30 on the normal 18 p.a. subscription or 11.70 on the
cost of buying twelve issues from a newsagent.
As we
is now
Electronics & Wireless World is published monthly USPS 687-540 Current issue price 1.95, back issues
(if available)
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Wireless World, Quadrant House, The Quadrant, Sutton, Surtey SM2 5AS. Cheques should he payable to Business
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(EEP) Facsimile: 01-661 2071 (Groups II & III) Beeline: 01-661 8978 or 01-661 8986. 300 baud, 7 data bits, even
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- send address to the above. Business Press International
Ltd 1986: ISBN
RADIOCODE CLOCKS LTD

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MINIATURE RUBIDIUM
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80 characters X 24
lines*
Requires ASCII encoded keyboard and monitor to

make fully configurable intelligent terminal. Uses 6802
micro and 6845 controller. Program and character
generator (7 X 9 matrix with descenders) in two 2716
EPROMs. Full scrolling at 9600 baud with 8 switch
selectable rates. RS232 interface.
Bare board with 2 EPROMS and program listing
48 plus VAT. Assembled and tested -139 plus VAT
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MATURE, FRIENDLY EPROM PROGRAMMER

SANG -OF-EIGHT
Option
Two Key operation
DATAI11Afl
Redesigned to Your
Specification
GANG -OF -EIGHT is a successful
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Since the launcr we have taken
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by engineers who have called us.
This gave us a wish -list of extra
features and revisions to work by.
The result is an improved G8
which should suit you even better
it is just what you asked for.
G8 was intended as a fast, lcwcost prcdu-tion copier, but f-equent enquiries made us think
again and design a version which

could be used for development
purposes, capable of uploading
and downloading in a variety of
INTELHEX,
formats:
serial
MOTOROLA S, TEKHEX, ASCII HEX anc BINARY. Links on your
serial cEble select the format.
already, reporting any which

match the master. Then G8 tells
you if any are not blank, so that
yoJ can erase them. Only if the
EFROMS pass these tests does
G8 start programming (but G8 will
unerased
try
to
program
EPROMS, if you ignore the ERASE
message and press START again
something else you asked
Quick delivery
25 and 27 Series to 512K
We knowyou don't want to wait, so

we keep ots of Gang -of -Eight programmer it stock. If you are in a
we will
real hurry telephone us
save your time and arrange the
for;.
G8 will handle 2516, 2532 and

2564 EPROMS, as well as all 27
Checksum Facility
G8 will calculate and display a 6 digit checksum of your master

EPROM, when you press START
and RESET at the same time. This
helos you to identify EPROMS
which are unlabelled, and provides a simple check on the
integrity of your data.
series from 2716 to 27512.
FAST and SLOW
Programming Method
You can use a FAST, intelligent
to program larger
EPROMS, which speeds up the
programming operation by a factor of five, at least. G8 will also program the old-fashoned way, with
50ms pulses.
algorithm
fastest delivery possible.
No Risk Trial:
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Without any questions asked, you

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G8 provides audible feedback, to
avoid the necessity for constant

monitoring
that is, it makes
noises so you don't need to watch
it: rising and falling arpeggios as
the program starts and finishes;
occasional tones to remind you
that your EPROMS are ready.
Data is audible when uploading
and downloading.
Voltage Selection
There are three di-ferent voltages

selectable (by switches) and
these are each resettable (by
potentiometers) over a wide
range. The factory -setting is 25
volts, 21 volts and 12.5 volts.
Liquid Crystal Display
Option
G8 shows the EPROM type, the

Program -Method and the Pro-
Datamar
Lombard House, Cornwall Road,

Dorchester, Dorset DT1 1 RX
England
Telephone: (0305) 68066

Telex: 418442 DATAMN G
add for RS232 option
add for steel case option
toc
GANG -OF -EIGHT
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postage is trae BUT please add VAT in U.K
41CRG ENGINEERING
EPROM programmer
carriage
Terms
- Steel Case
GONG -OF -EIGHT
only
Cheque with order or credit-card.
G8 normally comes in a plastic

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However, some of you want your
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gram -Voltage anc changes the

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- Bidirectional
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START
G8 has only two keys
and RESET
simple to operate,
yet it does all the useful things you
need. Before every programming
cycle it checks that you have not
programmed any of the EPROMS
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MICROKIT LIMITED
0327 860130
Blakesley Towcester, Northants NN12 8RB.

IC OM
raft/Linft_'
IL'c
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Communications
QUALITY FIRMWARE FOR ACORNS

BBC
THE MATRIX ROM

ELECTRON
'B','B+' and
Written with the co-operation of Southampton University this ROM uses

BASIC commands to perform matrix operations and the solving of linear
simultaneous equations. An indispensable tool for Engineers, Scientists and
Mathematicians.
36.00 (plus VAT) includes Manual. (Quantity discount.)
REPLAY Tape to Disc Transfer.
BBC 'B' and 'B+' (Most DFS types).
The only transfer system which has been acclaimed by independent
reviewers. Best transfer system available. Mid -play 'stop and save'. Pause
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35.00 (incl. VAT) Please state DFS type when ordering.
THE ADDCOMM ROM
BBC 'B', 'B+' and ELECTRON
A Toolkit/Graphics utility adding 40 extra BASIC commands. Brilliant
programming and value for money.
28.00 (incl. VAT) includes Manual.
WRITE -PROTECT SWITCH
ICOM introduces the IC -R7000, advanced technology, continuous coverage

communications receiver. With 99 programmable memories the IC -R7000
covers aircraft, marine, FM broadcast, Amateur radio, television and weather
satellite bands. For simplified operation and quick tuning the IC -R7000 features
direct keyboard entry. Precise frequencies can be selected by pushing the
digit keys in sequence of the frequency or by turning the main tuning knob.
FM wide/FM narrow/AM upper and lower SSB modes with 6 tuning speeds:
0.1, 1.0, 5, 10, 12.5 and 25kHz. A sophisticated scanning system provides instant
access to the most used frequencies. By depressing the Auto -M switch the
IC -R7000 automatically memorises frequencies that are in use whilst it is in the
scan mode, this allows you to recall frequencies that were in use. Readout is
clearly shown on a dual -colour fluorescent display. Options include the RC-12
infra -red remote controller, voice synthesizer and HP- I headphones
Please rush me details of the IC -R7000 and my nearest ICOM dealer.
Name
8.95 (incl. VAT) Simple fitting instructions included.

BBC "B+ to B" CONVERSION KIT
BBC 'B+' only.
Enables BBC 'B' tapes to be used on the 'B+' computer. (0.S.1.20 ROM
necessary.)
15.95 without 0.S.ROM -21.95 with 0.S.ROM.
(Both prices include VAT.)
Leaflets giving further information and reviews, where available, sent on
request.
All
Address
Tel:
Post to: ICOM, Thanet Electronics Ltd., Dept W W, FREEPOST,
LRerne Bay, Kent CT6 8BR. (no stamp needed).
Tel, 0227 363859.

fi
Acorn 'Master' only

the computer and offers write -protection to
A small module which plugs into

the Sideways RAM banks.
items direct and post paid from:
VINE MICROS, MARSHBOROUGH, Nr. SANDWICH, KENT CT13 OPG

Telephone: 0304 812276
or through your local Dealer.
WHY STRUGGLE WITH ALLTHIS?

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The new and ingeniously
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MODE 3
DIGITAL STORAGE SCOPE
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The ETL 3800A can be
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signals.
MODE 2
SPECTRUM ANALYSER
frequency range DC
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CONVOLUTION
this feature performs the
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Mobile radio's
many options
Changing economics and increased awareness have
made mobile radio one of the largest growth areas
in communications
MARK NELSON
that
Private mobile radio
mobile radio activity, just

as broadcast radio and
television, is carefully regulated to avoid chaos on the airwaves, and all use of radio
must be licensed. While the
regulations, which are administered by the Department of
Trade and Industry (DTI), are
more liberal than those in
(p.m.r.) or two-way radio is

the most common type of busi-
some other countries, the

amount of radio spectrum
companies and the nationalised industries use p.m.r. Fire,

police and ambulance authorities have similar systems;
It is wise to recall
available for private radio is

limited. As a result, new users
ness radio and gives a private

channel of communication be-
tween mobiles and
a base
station. Systems range in size
from a taxi radio net covering
small town to national

schemes employed by large
undertakings. Both private
a
Messages up to 90 characters long can be received on this

will find they must justify display pager, which has a memory capacity of 512 characters. A these are technically not
their proposals, and applica- built-in clock time -stamps each item.
classed as p.m.r. although the
tions which could be satisfied
techniques are identical.
with the use of landlines or the normal
There are several British manufacturers of
Transport firms and service engineers all
telephone network are unlikely to suc- mobile radio equipment, such as Philips make extensive use of p.m.r. and the demand
ceed. In many districts acute frequency (Pye), Marconi and Burndept/Dymar, while grows as more firms realize the economies
shortages already exist and new users other equipment is imported from the USA, which can be made by better use of their
may well be asked to share with existing New Zealand, Scandinavia and Japan and
fleets and personnel. Most equipment supones. It was this shortage of airspace sold either under the original manufacturpliers will demonstrate costed examples of
which led the government to turn over er's name or with a more familiar British the savings achievable by the use of p.m.r.
the v.h.f. channels formerly used for label.
Most p.m.r. operation has been on v.h.f.
black -and -white tv broadcasting to mobile
While channels may be shared, the actual
up to now, but the use of u.h.f. is increasing.
and other radio purposes.
equipment resources are normally owned The public utilities are located in mid -band
(or leased) exclusively by the user. An excep- v.h.f. but are starting to move to new
tion is the aerial site, which must be promin- allocations in high -band; the bulk of private
EQUIPMENT CONSIDERATIONS
ent for good radio coverage. Users may well business radio is in v.h.f. high -band, with
As well as a licence most radio equipment
rent space on a shared radio tower; this some on low -band.
also requires type approval. This is granted solves potential planning permission probIncreasing demands on the radio specby the DTI and indicates that the sets meet
lems as well.
trum are forcing new users into u.h.f. (below
Another principle is that connection into
certain technical and reliability standards
the tv broadcasting channels), which in turn
and will not cause interference to other the public telephone network from mobile is displacing the fixed point-to-point links
users of the airwaves. Private radio users are radios is not normally permitted *(except of previously accommodated here.
not trained radio operators and need to use course from sets which are radiophones); on
A variety of modern sets is available from
equipment which requires neither regular the other hand many private radio users can the manufacturers; many incorporate modadjustment nor special technical skills to use dial into internal private telephone systems.
ular components and design techniques,
Few business radio systems can guarantee
it.
simplifying maintenance and the change of
Type approval is normally undertaken by security of speech and users requiring total
band if necessary. Hand portable sets (HTs or
the manufacturer or importer and is not a confidentiality will have to fit additional handy-talkies) are obtainable, as well as
hurdle enountered by the end user. Most scrambler devices. The new cellular and mobiles, for those applications which remobile radio equipment is supplied by spe- trunked services are difficult to eavesdrop
quire them.
cialist dealers (listed in Yellow Pages) and effectively, however, because of the dynamic
While frequency synthesizers have rethese will normally assist with licence ap- reallocation of channels as mobiles move placed individual crystals for each frequenplication as well.
around.
cy, channel selection is manually switched
to conform with DTI regulations.

A wide selection of mobile and fixed aerials
is also supplied.
RADIOPHONE AND
MESSAGE-HANDLING
Another form of mobile radio, not necessarily an alternative to p.m.r., is public
radiophone. This is not a British Telecom
monopoly, although the British Telecom
v.h.f. system is the only direct -dial system
with virtually national coverage. But there
are several other networks with connections
handled by operators, for example Securicor
and AirCall. Most of these systems allow
phone calls to be made and received on the
move, just as from a normal phone.
Other systems - without ìnterconnect' operate on a message -handling basis and
direct conversation with the telephone subscriber is not possible.
In metropolitan areas demand for v.h.f.
radiophone service was until recently high
and the lack of additional channels for
expansion led to long waits for joining the
service and to make a call; it also increased
the pressure for the introduction of the new
cellular systems and plans for additional
private v.h.f. systems. The availability of
cellular radio (mentioned next) put an end to
these problems and the capacity of v.h.f.
systems now more closely matches demand.
Despite the availability of the cellular
alternative there is still a distinct market for
the v.h.f. services, which is being stimulated
by aggressive pricing of the subscriber
equipment.
THE CELLULAR SOLUTION
Cellular radio is a specialized form of

radiophone operating on much higher frequencies (900MHz), above the v.h.f. television broadcasting band. The shorter coverage of transmissions at these frequencies is
This synthesized ratiotelephone from Zycomm has a microprocessor -based selective

calling system. Among the first users is the Northern Ireland Electricity Service.
exploited by making the areas covered (cells)

much smaller and re-using the same frequencies at other locations. This gives the
system greater capacity and another byproduct is much improved speech quality.
Sophisticated computer control techniques are employed to ensure that the call is
not lost when the user moves from one
transmitter area into another, and if a set
(cellphone) is temporarily not in use a caller
can be informed of this and diverted if
necessary to an answering service or conventional wireline telephone.
The cellular system also caters for data
transmission, allowing the use of portable
computers and telex and fax machines out in
the field, although preferably when the
vehicle is static. Celphones are now starting
to be introduced for use as payphones on
trains and long-distance coach lines, and
within the cellular service areas they provide
better results than their high -band v.h.f.
predecessors.
Another specialized application is cell -
phones with outward dialling restricted to

one or more predetermined numbers: the
fixed telephones are linked by direct line to
the cellular exchange and the total system is
a form of national p.m.r. without the cost of
setting up a national network.
CELL COVERAGE
There are two competing cellular networks,
both connected to the public telephone
network. One is operated by Securicor in
partnership with British Telecom: this is
known as Cellnet. The other system, run by
Racal, is known as Vodafone.
Despite minor technical differences, both
networks offer comparable facilities at similar prices and have broadly the same coverage areas. Transmitters cover virtually all
towns and cities of significance, together
with the motorways linking them and much
of the countryside in between. Coverage has
also been extended to coastal regions and
cellphones work for considerable distances
out to sea; for instance, across the English
Not just for breakers: the Delta 1 from telecomms. Users of 934MHz equipment include even BT, which has bought some for
its maintenance engineers at Goonhilly.
CHANNEL
MEM
CLEAR
AUTO/
MANUAL
SEARCH
New budget price mobile
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Infinite VSWR Protection
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VISIT OUR STAND AT COMEX
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The UKV62 is a single

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Transceiver; totally British
designed & built to compete
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The UKV62 was formulated to
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systems with equal ease.
STAND No.
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UKV62/4 160-175M Hz
UKV62/9 420-470MHz
COMMUNIQUE UK LTD.
COMMUNICATIONS HOUSE
PURLEY AVENUE
LONDON NW2 1SB
TEL: 01-450 9755 TLX: 298765
MMUN/Q UE
17632
MIDLAND SYNTECH
QUALITY QUARTZ
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50kHz
Our frequency, ranges are:

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100MHz 250MHz 360MHz
Professional Crystals
We also supply quartz crystal filters.
oscillators of all types and

communication antennae.
Webster Electronics
ILMINSTEA, SOMERSET TA19 904, ENGLAND
TEL: (046 05) 5166 TELEX: 46571 FRONCY G
FAX (046 05) 5665
CIRCLE
Up to 80 channels, multiple CTCSS, scan,

5 Tone and numerous options VHF hiband
handhelds and mobiles both dash and
trunk mount all UK type approved at a price
that you can afford.
For further details contact:
School Close,
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Tel: (04215) 55111
Tlx: 477351
\
i;,',''\`
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___
Fax: (04215) 63507

10
all)
19
FOR FURTHER DETAILS
DISTRIBUTION
AMPLIFIERS AND FILTERS
for mobile radio applications.
A range of reliable, high performance,
products from
beronheath llmlted.
Applied Radio Frequency Technology
Bradworthy. Holsworthy, Devon EX22 7TJ

(0409 24) 548. Telex 42513 Sharet G
legitimate users of the frequencies pirated.

For this reason the government is introducing strong penalties to curb their sale and
use.
Channel at its narrowest point.

Both networks are well ahead of schedule
of their quoted expansion plans and user
take-up has far exceeded expectations. Eventual coverage is planned to include 90% of
the population and 64% of the UK landmass, but there will not be the same degree
of national coverage as on the v.h.f. systems.
Cellular offers for the first time pocket and
briefcase size hand-portable radiophones
and the facility to receive dialled calls from
overseas. Other innovations are continuity
of conversation when transferring from one
transmitter area to another (known as handoff) and speech quality which, at its best, is
far better than on previous public
radiophone systems.
CHANNELS CRISIS
PAGERS AND-PINPOINT
Apart from p.m.r radiophone and cell phones, there are radio systems intended for
other specific uses which may offer an
alternative. These are radiopagers and personal or citizens' band radio.
Radiopagers or bleepers can be short or
long range: local on-site systems are normally privately -owned for staff location purposes and cover just one building or area.
Wide -area networks, on the other hand, can
cover a complete city or the whole country
and are operated by organisations such as
AirCall and British Telecom. In some cases
users can be alerted by dialling a special
telephone number and the actual call may be
a bleep or a spoken message. There are also
Pocket Telex or Message Master pagers
which display a complete message which can
be sent by an operator or by any person with
access to a data terminal connected to the
telephone. The largest national network is
operated by British Telecom and is linked to
the public telephone network, so that a user
may be paged with a free call from any
phone.
This system is for tone or display messages
only: it cannot handle spoken messages. On
the other hand the pager units (bleepers) can
give up to four distinctive tones which can be
assigned to different messages (ring home,
call the office, etc.). Group call - for instance
to alert a complete sales team - is also
possible.
In all cases people who have been paged
can make a phone call to receive a message,
and this may be an acceptable substitute for
mobile radio.
An innovative use of radiolocation is
Pinpoint, a tracking system for vehicles
provided by British Telecom initially in the
London area. Vehicles equipped with the
system signal to the base station their
location, which is determined by a combination of dead reckoning techniques and
checking by low -power radio beacons. The
cost of the system has restricted its use so far
to vans carrying high -value loads.
THE CITIZENS' ALTERNATIVE

A relatively unsophisticated but low-cost
alternative to p.m.r. is 934MHz personal
radio or u.h.f. citizens' band.
Far removed from the 'breaker, breaker'
image which taints the 27MHz c.b. system,
this band is relatively under -used and is ideal
The Tele-Niros v.h.f. hand -portable is supplied with up to four channels and with
open or selective calling (Tele -Nova Ltd).
for short-range, non -essential communication (up to 5 or 10 miles). Professional

quality radio equipment made in Japan is
now available at around a third of the cost of
p.m.r. and speech quality is as good as
cellular radio.
As the band's 20 channels are used mainly
for leisure purposes they are largely empty
during business hours, and in rural areas
this is already being exploited by veterinary
surgeons and taxi firms.
A more sophisticated variant, currently
under examination by the DTI, is a system
known as PRS (personal radio service) or

SRR (short range radio). Based on Japanese
experience and already in operation there
and in Switzerland, it uses similar 900MHz
frequencies but with the addition of selective
calling and dynamic channel and allocation.
To use the system the calling station keys
in the number of the set required and presses
the push -to -talk key. The digital code of the
desired set is sent on a shared data channel,
which is monitored by all idle sets. If the
called station is switched on it replies automatically, causing the sets to scan the
channels available to find an unused one for
the conversation. All this is achieved in an
instant.
The combination of these features and the
f.m. system give privacy and an absence of
interference.
Sets for this type of system cost around
400 in Switzerland and offer a potentially
attractive system for small business and
leisure users alike. As no repeater transmitter its used the range is limited, however, to
around three to five miles and the system is
no substitute for wide -area mobile radio.
CORDLESS PIRATES
Cordless telephones - sometimes confused
with cellular radio - do not come into our
consideration since these are purely shortrange (about 300 feet) extensions of fixed
telephones. Although high-powered and
mobile versions exist these are not licensable
in the UK and their use is likely to end in
grief, as well as causing interference to
Whilst all the sectors of mobile radio are

growing, it is p.m.r. which shows the
greatest expansion as users find it more
affordable and essential. A problem is the
shortage of frequencies: recently it was
asserted that in the spectrum between
30MHz and 1GHz the allocation to p.m.r.
was only 8% and that of this only 20% was
usable.
Partly to counter criticism that too much
spectrum is allocated to defence uses, a
three-man team of eminent authorities has
been appointed by the government to carry
out a study of the military's use of radio
frequencies. The first stage of the study,
which is due for submission by December
1987, will concentrate on the frequency
range 470-3400MHz.
Another study group is examining the
potential for more commercial pricing of
available spectrum, with the possibility that
frequencies would be sold to the highest
bidder. No such system is employed anywhere else in the world, and it has clear
dangers. In the meantime, however, fees for
some mobile radio licences have been raised,
in some cases substantially.
Of Britain's 300,000 or so vehicles fitted
with two-way v.h.f. or u.h.f. radio, some
50,000 are in London, with a waiting list of
18 months for frequencies. Several solutions
to the frequency shortage are now being
developed, involving both new frequencies
and new techniques, both separately and in
combination.
TRUNKING TECHNIQUES
In Band III (v.h.f. high -band) the government has indicated its intention to reallocate
channels to new national private mobile
radio networks, as well as to public utilities
displaced from Band II channels required for
the extension of f.m. broadcasting.
The new national systems will offer the
advantage of a ready-made p.m.r. service on
which users can rent as many channels as
they require, without the need to set up their

own system. Sophisticated selective calling
systems will ensure that users receive only
messages intended for them and do not
interfere with or overhear other users. Limited interconnection with the public telephone network may be permitted (in offpeak hours).
The service is likely to open in January
1987 and will offer both voice and data
services provided by two operators, GEC and
a consortium of Pye, Racal and Securicor.
Trunking techniques, already widespread
in North America but new to Britain, will
enable a larger number of uses to share a
pool of frequencies. Radio sets pick the first
free channel from the pool, which is controlled by a computer: users are connected
automatically and are unaware of the actual
channel being used, which will vary from
occasion to occasion in a similar way to
cellular radio.
11
A number of trunked systems are now in

operation, though user take-up has not
entirely matched expectations, probably because the offerings do not share the glamour
(or the amount of media exposure) cellular
radio has achieved. Another factor may be
the higher cost of the sophisticated equipment, even though it is offset by the economies possible and the opportunity to beat the
waiting list.
COMMUNITY REPEATERS
lower-cost solution, which also uses scarce

radio resources more economically, is the
community repeater or base station. Frequencies are shared by a number of users
and tone -squelch systems are employed to
prevent overhearing. Light signals indicate
whether the channel is free or in use, and
calls between mobiles and the various users'
base stations are relayed by a well -sited
communal transmitter or repeater station.
Other new techniques currently under
investigation aim to make better use of
A
frequency resources, and include
transparent -tone -in -band and tone -above band systems for shared speech and data. In
addition there are revertive and overlay
paging systems which can be added to
existing p.m.r. systems to alert mobile users
to a call when they are away from the vehicle.
SATELLITE POSSIBILITIES
Looking to the longer term, future mobile
radio systems may rely on satellites to give
wider area coverage and to increase the
number of users accommodated. A number
of schemes have been presented for consideration.
In the United States, papers have described how a geostationary satellite could
extend cellular radio service into rural and
remote areas which are either impossible or
uneconomic to cover by terrestrial transmitters on account of low user density. Fixed
telephone service to isolated homes could
also be provided at lower cost by satellite
than conventional wireline.
A British proposal by a number of UK
universities and the Rutherford Appleton
Laboratory envisages a satellite paging system whereby cellular telephone users are
paged by satellite when a fixed telephone
caller wishes to get in touch. Such a satellite
system would also have advantages in situations where terrestrial radio systems were
MHz frequencies desired for this kind of

service are unlikely to be allocated.
Any eventual service is more likely to be
accommodated around 1.5GHz, with corres-
ponding higher equipment costs.
THE PROSPECTS
FOR MOBILE
Mobile radio is now the most dynamic sector
of the telecommunications market, and user
awareness is greater than ever before.
Opportunities for manufacturing and
sales are being seized aggressively. urrently the British market is served mainly by
British and associated European producers,

with a growing percentage of USA and
Japanese imports. Three firms, however,
have set up plants for the manufacture of
cellphones, which augurs well even if large
numbers are still imported from Japan. With
luck, the continuing boom in demand will be
matched by a supply situation which satisfies
the best interests of all concerned.
not yet harmonized or standardized,

although potential frequency clash may rule
out this solution in Europe. Geographical
and economic considerations make this
scheme more likely to take off in North
America, although even there the sub -1000
This article is an expanded and updated

version of one which originally appeared in
The Mobile Telecommunications Guide '86,
edited by Adrian Morant and published by
IBC Technical Services Ltd.
Wide -area binary paging

Many mobile communication requirements can be
satisfied by one-way data transmission. And as the
prospect of spectrum pricing looms, attention is turning to
paging networks as an effective low-cost alternative to
radio telephones. This artile explains how a radiopaging
system works.
J.C. KIRBY
wide area paging system, almost by
definition, needs many radio transmit ers to provide the high field strengths
needed for an effective service. The antennas
inside pagers are not as efficient as vehicle
antennas, and so more transmitting sites are
required to provide coverage similar to that
of p.m.r. systems.
Nevertheless, at many locations within a
zone, pagers will be receiving signals from
more than one site. If each transmitter were
to transmit its message in sequence, not
only would most pagers receive duplicate
calls, but valuable air time would be wasted
because subsequent calls would have to wait
until the previous call had been transmitted
at each location.
Quasi -synchronous operation (or more
simply, simulcast) is the solution. This
technique allows transmission from all locations within the zone simultaneously; but
care must be taken to ensure that when a
pager receives signals from more than one
source, the signals combine in a beneficial
manner. This can be achieved by careful
system design.
Radio signals in the proximity of buildings
are reflected, causing interference patterns
with non -reflected signals resulting in small
12
(less than half-a -wavelength) areas where no

signal is received (nulls). Users of hand portable radio sets will be familar with the
effect a movement of only a few inches can
make to the strength of a wanted signal in an
urban environment.
Introduction of signals from a second
transmitting location creates another pattern of nulls. The areas of no signal are now
only those where nulls from both sources
coincide. Small movements of the receiver
now have less effect on the strength of the
received signal.
Correct quasi -sync operation occurs when
the modulation from all transmitters in the
system is identical, both in phase and amplitude. The level of the modulation, whilst
very important for voice quasi -sync systems,
is fixed for binary data. It may take only two
possible values, +5 or -5kHz of the operator's frequency. During normal operation,
the transmitter never actually radiates on
the centre frequency, that which appears in
the licence!
Absolute synchronization of the carrier
wave is not required, but a high -stability
frequency source should be used to maintain
constant low -frequency offsets between
adjacent sites.
Surprisingly perhaps, simulcast proves

easier to implement for the transmission of
data than voice. Let us consider why.
PHASE -DELAY TOLERANCE
Human speech transformed into an electronic signal gives a complex waveform. Analysis of this waveform reveals a mixture of
frequencies at differing amplitudes with
different phase relationships. Voice frequencies range from 40Hz to 15Hz, but only
frequencies between 300 and 3000Hz are
required to provide reasonable speech
quality for private radio systems.
Consider a voice signal divided into two
channels, one of which is delayed by lms. All
speech frequencies at 1kHz on the delayed
channel will be 360 behind the undelayed
channel. A 360 phase difference is, to the
human ear equivalent to no phase difference; and so the 1kHz part of the speech
would sound undistorted if the channels
were re -combined. Frequencies of 2kHz and
3kHz with 720 and 1080 phase difference
would also sound undistorted.
However, those components of speech at
500Hz will be 180 out of phase and will try
to cancel each other. Components at 1.5kHz
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13
TABLE I: delays in a typical system configuration
with landline distribution

1200 baud modem:
Radio link transmitter.
Radio link receiver:
Landline:
Paging transmitter.
Paging transmitter rise -time:
Delay equalization unit range:
180s
140s
200s
10s/mile
140s
250s
min.30s
max.50ms
Adjusted for
50ps delay
and 2.5kHz with 540 and 900 phase difference will also try to cancel, and the ear would
certainly notice differences at these frequencies.
Speech systems demand not only that
delay differences are minimized between
sites, but also that any variation of delay over
the frequency band (the group delay) must
also be constant. Data occupies less band
width than speech and so the group delay
problem is less significant.

Data must therefore be radiated from each
site on the system in phase. But how can this
be done when these sites are varying distances from the paging exchange, and longer
landlines mean longer delays? Let us now
discover how closely this data must be
synchronized between transmitters.
DELAYS
Tests show that the maximum delay difference which can be tolerated on a voice
channel is about 10% of the period of the
highest modulating frequency (3kHz),

which amounts to 33 microseconds.
The same calculation can be applied to
binary signalling. The maximum bit rate is
512 bits for current generation radiopaging
code and tests in Japan during 1977 found
that at low signal levels there should be no
more than 25% confusion period in any one
bit. (The confusion period is the time between transmitter 1 changing from binary 0
to 1, and transmitter 2 changing from 0 to
1.) The maximum delay difference in
seconds is therefore 1/512x25%, or 488
microseconds.
If the pager is not midway between two
Fig.3. How voice -messaging works. Instructions and warnings to the caller are in
speech form too.
Standard
telephone
or
cellular
Links
Stores
t
Direct d,at
Torte
Voice
Number
Pagen=;
servic
paging&
messaging
exchange,
Word
Transmitted
Retrieves
Subscriber
retrieves;
receives
a message
".
Line A delay =170ps
Line
Fig.1. Typical system
delay
220ys
configuration: landline distribution.
An office viewdata terminal can be used to send calls to radiopagers or to retrieve

stored messages.
Link
receiverA
Link path A propagation
delay of 75ps
Modem A
Delay
equ.
Link path
Adjusted for
30}s delay
Link
propagation
delay of 45}s
Fig.2. Typical system configuration: link distribution. Delay is essential
unit
receiver 8
for quasi -synchronous working.
telephone number to ring and the pager

number to ask for.
If the numbers can be combined into a
-digit telephone number, the 'phone
ten
2
is
example, if site 1 is 20km away and site
number itself then indentifies the pager.
10km from the user, the path difference is
And, because the paging exchange has a
10km. Since radio signals propagate at
3.34s/km, the speed of light, the signals database, the number also indentifies which
arrive at the pager with a delay difference of service the caller expects. Changes of pager
33.4s. As the path differential increases, or extension of service need not mean a
change of 'phone number.
the likelihood is that the signal from the
Digital Mobile Communications operate
nearer transmitter will completely capture
such a direct dial service; all numbers are ten
the receiver, and effects from the more
digits long. The first five digits route the call
distant site will be eliminated.
Equipment used in distribution and trans- from any telephone in the UK into Digital's
mission of the data introduces additional PX2000 radiopaging exchange. Digits 5 -10
(99 999 numbers) are presented to the
delay. Some typical values are given in Table
paging exchange on up to 32 trunks. The
1.
PX2000 responds according to the service
The delay equalization unit is an essential
part of any quasi -synchronous system. It allocated to that number. Services are:
tone -only paging
compensates not only for variations between
tone -and -voice paging
modems and transmitters due to manufacmessage paging
turing tolerances, but also for different
voice messaging
landline or link path lengths.
retrieval of voice messages
Usually the most remote site exhibits the
number not allocated (returns `number
greatest distribution delay, and is taken as
unobtainable' tone to caller)
reference. Other sites having less delay now
Following a call to a tone -only pager, the
have to be synchronized with the reference.
phrase
"call accepted" is spoken automatiis
made
to
unit
The delay equalization
introduce additional delay such that delay to cally. A call to a tone-and -voice pager is
answered by the exchange which announces
all sites is equal. Only then can the benefits
the number dialled and invites the caller to
of quasi -synchronous operations be realized
leave a message. It is reassuring for the caller
fully.
Suitable binary delay units are not readily to hear a human voice rather than bleeps.
available off-the -shelf and at least three of Fewer calls are abandoned because of confusion or the "I don't like talking to a machine"
the network operators produce their own
syndrome.
units in-house.
The length of a voice paging message is
restricted to fifteen seconds, after which the
ACCESS METHODS
caller hear the words "call accepted". The
message is sent immediately to the pager,
operthe
system
Often callers telephone
but remains stored in a digital form on disc
ator's message bureau, are answered by an
in case the user wants to retrieve it again
leave
a
number,
a
pager
operator, quote
later.
message and ring off. The message is entered
Display -pager calls are diverted to an
by means of speech or keyboard usually by
operator, and at the same time the pager
the operator who answered the call. This
method occasionally resembles `Chinese user's details are sent on to the operator's
whispers', especially with the handling of v.d.u. The operator answers the call, usually
technical or coded messages. In addition, all with the user's company name, and takes a
callers must remember two numbers: the message.
transmitters, yet is receiving signals from

both, then the user is introducing more
confusion time by virtue of location. For
Voice mailbox calls (Fig.3) may or may not

initiate a page. On answering, the voice of
the mailbox subscriber (stored in digital
form on disc) is played to the caller. Callers
are usually invited to leave a message, by
speaking after a tone. A linking feature
within the exchange automatically informs
the subscriber, by means of paging, that a
message has been taken.
A time limit of 30 seconds is placed on
voice mailbox calls. If they exceed it, callers
are informed, and told that the first part has
been recorded. Mere pips could never explain that!
Retrieval calls are also routed to the
paging exchange. Only the subscriber knows
his retrieval number, and incoming calls are
played back automatically. Some of Digital's
subscribers want a higher degree of security
on collection of messages, and so a touchtone pad is available to give password indentification. The exchange speaks the words
"Please enter your password" on answering.
Use of a d.t.m.f. pad allows the subscriber to
change or re-record the answer phrase as
required.
OPEN ACCESS
The use of data terminals over public telephone lines is ever increasing. At last,
viewdata is gaining popularity in the business world, and the choice of terminals is
growing. Digital find that many subscribers
with a dozen pagers or more are likely to
have a Viewdata terminal in the office
already, probably to access Prestel or some
similar service.
Subscribers are often surprised to learn
that the terminal can also be used for
sending calls to message and tone only
pagers. Retrieval of messages is another
facility offered to Viewdata users.
To be continued.
Chris Kirby is technical manager of Digital

Mobile Communications Ltd, which operates one of the four wide -area binary paging
networks in the UK.
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CIRCLE 8S FO t FURTHER DETAILS

16
Viewing the p-esent. Modern cameras at the Royal Wedding.
BBC television looks back
and forward
It is 50 years this month since the world's first high definition television service opened. Pat Leggatt reviews
progress and looks ahead.
D. P. LEGGATT
Fifty is a nice round number and a good
basis for Golden Jubilee celebrations.
But this year sees several different

anniversaries of the BBC's association with
television, the first being an even more
venerable Diamond Jubilee.
It is just over 60 years since, in July 1926,
television signals were first radiated from a
BBC transmitter. The brief experimental
transmissions, from the medium wave 2L0
on the roof of Selfridges, carried 30 -line
vision signals supplied by Baird.
Next in line is the 57th anniversary of the
start of the regular experimental transmissions, again from the BBC's 2L0 station, in
August 1929. The programmes came from
the Baird studio at Long Acre but, since only
one transmitter was available, the audience
could be offered pictures or sound but not
both at the same time. A few months later, in
March 1930, simultaneous vision and sound
was radiated from the new twin transmitters
at Brookmans Park.
We must now note the 54th anniversary of
the BBC Television Service. In August 1932 a

BBC television studio in the new Broadcasting House took over programme production
from Baird (still on 30 lines) and the BBC
Television Service was born. It started with a
staff of one, in the person of the engineer
Douglas Birkinshaw, who supervised the
installation of the studio equipment supplied by Baird.
Passing over the closure of the 30 -line
service in 1935, we come finally to the 50th
anniversary of the world's first regular high
definition television service. The BBC 405 line service from Alexandra Palace was formally opened on November 2nd 1936, alternating each week with the Baird 240 -line
system until February 1937, when 240 -line
transmissions ceased. Even this 50th
anniversary date must be slightly hedged, in
that a 10 -day preview of the service had been
transmitted for the Radiolympia show from
August 26th, followed by trial programmes
on an irregular basis during September and
October.
Despite the earlier events, regular television of real entertainment value started in
November 1936 and it is to this date that the
BBC now looks back.
THE PRE-WAR YEARS

Things started on a fairly modest scale. In
Alexandra Palace in the early days there were
two 2000 sq. ft studios, each with three
Emitron cameras; studio sound and lighting
control equipment; two telecine machines
comprising intermittent -motion projectors
with Emitron cameras; and the vision and
sound transmitters. Although not lavish,
this complement offered the essential tools
for production and a good range of programming was achieved, including outside broadcasts in the grounds of the Palace as far as
the weather and the 1000ft camera cables
allowed.
In early 1937 the Post Office installed a
balanced -pair vision cable from central London to Alexandra Palace, enabling the first
major outside broadcast to be undertaken on
17
Forseeing the future.
A BBC
satellite terminal at Kingswood Warren in Surrey.
the occasion ut the Coronation in May 1937.

Soon after this the BBC acquired two 3 camera o.b. vehicles and v.h.f. radio links, so
that a wide variety of outside events could be
covered. A considerable advantage for outside broadcast work was the introduction in
November 1937 of the Super Emitron. In
this camera tube the photo -electric emission
function was separated from the mosaic
target and the photo -electric efficiency
could be considerably increased: furthermore, this tube gave electron -multiplication
by secondary emission from the scanned
target. The Super Emitron was about twenty
times as sensitive as the Emitron, directly
useful in poor lighting conditions and useful
also in its potential for increasing the depth
of field of the camera.
On the telecine front, the Emitron was not
a very good tube for the purpose: and indeed
the quality of film reproduction was about
the only aspect in which the Baird apparatus
had been superior to the Marconi -EMI system. The spurious shading signals (tilt and
bend) of the Emitron proved very difficult to
correct in the film scanning application
where abrupt changes of scene lighting
balance could be expected: and because the
telecine system involved a brief flash exposure during the scanning flyback period, the
resulting large Emitron "photo pulse"
proved troublesome. This latter difficulty
was later removed by replacement of the
intermittent -motion projector by a Mechau
film transport in which successive tilting
mirrors produced a stationary image from
continuously moving film. The Emitron
could therefore be exposed for the full
18
television field period, avoiding the "photo in succeeding years, many in the form of
pulse" and incidentally taking advantage of frequency transposers (with no demodulathe tube's storage capabilities to reduce the tion to baseband) specially developed by the
required illumination.
BBC. The last transmitter for the 405 -line
The Marconi transmitters, with antennas service was installed in 1970, the population
on the roof of the Palace, gave 34kW vision coverage finally achieved being 99.5%.
Nearly all the BBC 405 -line transmitters
e.r.p. and provided a good signal to London
and about 30 miles around. The audience were in v.h.f. Band I, with a few in Band III.
was, of course, slow to build up at first and by Only five television channels were available
August 1939, after which the service closed in Band I, and considerable ingenuity and
down for the duration of the war, there were care with geographical locations, choice of
some 23,000 licensed receivers.
channels and polarizations was needed to
achieve the final virtually countrywide
POST-WAR 405 -LINE
coverage. The adoption of vestigial-sideband
DEVELOPMENT
operation for all stations other than the
original Alexandra Palace transmitter was
Towards the end of the war, the Governvaluable in reducing channel bandwidth
ment's Hankey Committee decided that the
requirements.
television service should re -open on the
original 405 -line standard. British television
Programme -origination. On the
therefore returned in June 1946, the first
programme -origination front there was also
service in Europe to re -open.
an urgent post-war need for expansion and
Transmitter coverage. There were many enhancement. It was outside -broadcast facilities that first received attention, with imthings to be done, perhaps the most urgent
proved cameras using CPS Emitron tubes in
being to spread coverage beyond south east
1947; zoom lenses in 1949, with only 2:1
England and make the service a truly nationrange but still an important advance on lens
al one. By 1952, four new high -power
turrets; and a car -mounted Roving Eye
(100kW e.r.p.) transmitters had been built at
camera unit in 1954.
Sutton Coldfield, Holme Moss, Kirk
O'Shotts and Wenvoe, extending coverage to
Studio availability was expanded with the
81% of the population. Five medium -power acquisition of Lime Grove in 1950, the
stations followed, including one in Northern Shepherds Bush Empire theatre in 1953 and
Ireland and one in north east Scotland, the Riverside studios in 1956. With an eye to
giving 93.5% coverage by 1955. The Alexan- the future, a 131/2 acre site at White City had
dra Palace transmitter was replaced in 1956 been purchased by the BBC in 1949 for a
by one at Crystal Palace with an e.r.p. of comprehensive new Television Centre,
200kW.
although it was not until 1960 that the first
A number of low -power relays were added studio came into service there.
Regional studio facilities were not neglected of course, starting in a modest way
with a converted chapel in Manchester used
on a drive-in basis with equipment temporarily demounted from an o.b. unit. Later
regional expansion saw provision of major
production centres In Glasgow, Belfast, Cardiff, Manchester, Birmingham and Bristol,
with smaller studio centres in a number of
other areas.
Studio equipment steadily improved, with
the old Emitron cameras replaced by the
CPS Emitron (orthicon), Photicon (image
iconoscope), and 3in and 4'/ein image orthicon. Twin-lens flying spot telecine replaced
the Emitron camera types. Special effects
systems such as the BBC -developed inlay
and overlay offered new production
opportunities.
Video recording. In 1947 the first attempts
were made to provide the much -needed

facility of video recording. With a vision
bandwidth of 3MHz, waveform recording
was not then practicable and only image
recording on photographic film seemed
feasible. Using a conventional
35mm intermittent -motion film
camera directed at a television
c.r.t. display produced rather indifferent results, since the time
which had to be allowed for film
pull -down meant that only one
television field in each picture
period could be recorded. The resulting 2021/2 line structure produced obstrusive alias components when rescanned on tele cine.
This suppressed -field system
was later much improved by the
application of vertical spotwobble to the
displayed picture, thereby removing the line
structure; but a further advance was made by
storing the `lost" field in the form of afterglow
in the display tube phosphor and presenting
both fields simultaneously to the film during
its stationary period. The stored -field technique gave good results with stationary
pictures, but the long-persistence phosphor
gave rise to considerable blurring of moving
parts of the scene. This shortcoming was
eased by use of a special fast pull -down film
mechanism which, while not achieving pull down within the 1.4 millisecond field blanking period, at least left only a few lines at the
top of the picture to be recovered by storage
in a shorter -persistence phosphor.
Another approach was to use the Mechau
continuous film transport to immobilize the
television image on the film frame. This also
produced quite acceptable results, but the
mirrors on the Mechau drum required frequent and very careful adjustment to avoid
inter -frame exposure variations and move-
Standards conversion. Another important

post-war development of BBC television was
the introduction of international operations.
The first live programme from overseas was
in 1950 when pictures from a BBC 405 -line
o.b. unit in Calais were radio -linked back
across the Channel. In 1952 a French produced television programme from Paris
was standards -converted for UK viewers; and
1954 saw the first large-scale European
exchange with eight countries taking part.
For these early international exchanges,
optica' standards converters were employed
in which a display on the incoming standard
was exposed to a camera on the outgoing
standard. The performance of these optical
systems left much to be desired and investigations were later undertaken into purely
electronic methods. In 1963 the BBC developed the world's first all -electronic line
store converter, for interchange between
standards with the same field rate. Not only
did these converters give greatly improved
quality for European exchanges, but they
were ready to play a vital role in the mixed
405/625 economy which was to start in the
to secure maximum coverage without interference between UK transmitters, or between the UK and neighbouring countries.
The comprehensive computer-based system
has achieved better than 99% population
coverage of four services, a record unequalled on u.h.f. in any other country.
The coming of colour. Although the BBC's

opening on BBC2 in 1967 was the start of the
first colour service in Europe, the United
States had been operating in colour for many
years and the Europeans's late entry gave
them a valuable opportunity to build on
American experience.
Up to this point the American operations
and the British experimental work had been
conducted with three-tube image orthicon
cameras. The image orthicon was not well
suited to the task of producing three separate colour signals matched in grey -scale
and geometry; and of course the large tubes
resulted in a very unwiedly camera. Fortunately the Philips Plumbicon appeared just
in time to enable the BBC2 colour service to
start with cameras of excellent performance
and reasonable size. To begin
with, both the British manufacturers, EMI and Marconi,
produced 4 -tube cameras; but as
designers mastered the art of
tube registration, the necessity
for a separate luminance tube
disappeared and 3 -tube cameras
became standard.
Although the development of
colour studio equipment and
techniques required much ex pert and dedicated work, perhaps
the most innovatory aspect of
colour television was the coding
system. The American NTSC was well established and there was a strong movement in
the BBC for its adoption in the UK. In
Europe the French SECAM and German PAL
derivatives of NTSC had been proposed and
the CCIR recommended that European
countries adopt one or other of these. The
UK, and the majority of other Europeans,
opted for PAL.
30 lines, 405 lines, 625 lines,

1000+ lines: where will it all end?
The BBC looks forward, not to the
end, but to the centenary of
television, with the next 50 years as
full of progress and excitement as
ment jitter.
These film recording methods were of
course largely superseded by the introduction of the Ampex video tape recorder in
1958. In company with other broadcasters,
the BBC has followed the succession from
2in quadruplex to 1in C -format and other
helical -scan standards. The BBC has made
original contributions in the way of sophisticated video tape editing systems.
the last.
UK in 1964. A few years later, in 1967/68,
another BBC first was scored (and a Queen's
Award earned) with the all -electronic field

store converter for programme exchange
between 50 and 60Hz field rate systems.
THE 625 -LINE ERA
U.h.f. transmitter planning. Matching the
general movement in Europe, it was decided

in the early 1960's that British television, by The March of the Digits. Formany years the
then including ITV as well as the BBC BBC has been prominent in the application
service, should adopt 625-line standards of digital techniques to broadcasting. In
transmitted in the 'u.h.f. Bands IV and V. A 1972 the BBC developed the sound-in-syncs
new BBC service, BBC2, opened on 625 lines system whereby the sound content of the
in black and white in 1964; while BBC1 and television programme is carried within the
ITV waited for their 625 -line debuts until vision waveform as digital pulse code modulation during the line synchronizing
they went into colour in 1969.
Development of u.h.f. transmitter net- periods: this development was more or less
works was, and still is, undertaken as a joint coincident with that for distribution of
BBC/IBA project. Planning was for country- stereo radio programme in p.c.m. form to
wide coverage of two BBC and two commer- the v.h.f.-f.m. transmitter network.
Sound-in-syncs signals are decoded at the
cial services with co -sited transmitters
radiating all four services from a common transmitters and radiated in normal anaaerial at each site. The ownership and build- logue form: the first actual transmission of
ing of the stations is shared equally between digital signals to the viewer came with the
the BBC and the IBA, each being landlord at introduction of the teletext service in 1974.
half the sites and tenant in the other half. Digital teletext signals are transmitted durWith this co-operative system, the viewer at ing four or more otherwise unused lines in
home needs only a single aerial to receive the the field blanking period, and control a
four services.
character generator in the receiver. Recently
With only eleven 4 -channel frequency the system is being used to carry computer
groups available in Bands IV and V, very programs which may be directly loaded into
sophisticated frequency planning is needed a computer rather than displayed as screen
19
Stereo sound is of course a feature offered

by MAC; but we should quite soon be
Looking back. Remembrance day, 1946. Television cameras at the Cenotaph.
text; this application is termed telesoftware.

In the distribution of vision signals in
digital form, the BBC has done, and continues to do, significant work on bit -rate
reduction. Digitally coded 625 -line PAL has
been successfully compressed into a 34
Mbit/s channel; and good progress had been
made. in reducing the requirement for 625line component signals from the basic
215Mbit/s down to 68 Mbit/s.
Perhaps the most significant attribute of

digital operation is the ease with which
digital signals may be stored and subsequently manipulated. A relevant application
is standards conversion, where new lines and
fields can be synthesized from a digitally
stored input signal: the IBA's DICE converter of 1972 was a notable archetype; and the
BBC ACE equipment, storing four fields, is a
current leader in the market. Other BBC
exploitations of digital storage are the television noise reducer, in which random noise
in successive fields is averaged out while
coherent picture signals are preserved; and
the BBC -designed still picture storage

manufactured and marketed worldwide by
Rank Cintel as "Slide File".
20
THE NEXT FEW YEARS

might be expected, virtually all developments in the foreseeable future are likely to
be rooted in digital technology.
Television signal distribution, internationally, within the country, and within
studio centres, will increasingly be in digital
form with optical fibres providing an appropriately wideband medium. Already there are
signs of success in the search for methods of
switching signals in optical fibres without
intermediate conversion to electrical form.
The digital video tape recorder has been
seen in experimental form and is almost with
us as a commercial product. No doubt video
tape editors will soon find reason to go to one
hundredth generation dubbings!
Direct broadcasting by satellite will at last
emerge from its protracted gestation,
although not initially as a BBC service. It will
probably use one form or another of the
IBA's MAC system, in which the vision
components are analogue, but which qualifies as a digital development since the time
compression and expansion processes are
effected with the signals in digital form.
As
enjoying stereo with existing terrestrial television. BBC development of digital sound on
a second carrier within the 8MHz transmission channel offers stereo or dual -language
sound without the interference between
sound and vision which can be a shortcoming of second -carrier analogue systems.
Looming largest, perhaps, is the prospect
of h.d.tv; not the "high definition" television
of 1936, but with something more than 1000
lines. The choice of h.d.tv standards is a
'matter of international controversy, focussing mainly on acceptance or otherwise of
the Japanese 1125/60 field proposal. It is
generally agreed that this system gives excellent pictures, but many countries currently
on 50Hz field frequency have doubts as to
the acceptability of a 60Hz cuckoo in their
nest. It now seems that the problems of
impairment -free 60-50 fields standards conversion will be overcome to an acceptable
degree, but anxieties remain in such areas as
the 10Hz difference between 50Hz lighting
supplies and a 60Hz field scanning rate.
Two other outstanding problems made it
sensible for the recent CCIR Plenary meeting to postpone a decision on h.d.tv standards, pending further development work.
First, there is as yet no domestically convenient high -quality picture display device
capable of giving the large picture which is
needed for h.d.tv to be seen at its best. C.r.ts
of 36in or more seem unduly cumbersome;
and projection systems of adequate quality
and stability could be bulky and expensive.
The second problem arises from the large
bandwidth requirements of h.d.tv. In the
absence of special measurements, more than
30MHz is needed and this could not be
accommodated in the presently -planned
satellite broadcasting channels. Still pictures present no difficulty -a 1Hz bandwidth
will suffice if you don't mind waiting some
time for the picture to build up! It is moving
scenes that require high information rates
and the solution will probably lie in passing
additional information to the receiver to
enable its electronic processing to handle
moving areas in the best way.
The Japanese MUSE system transmits
signals limited in bandwidth to about 8MHz,
together with motion vectors related to
moving areas. A more advanced development is the BBC's digitally assisted television (d.a.t.v.) proposal in which a similarly
bandwidth -limited signal is accompanied by
digital data to assist receiver processing
towards the optimum treatment of individual moving areas within the picture.
HISTORY OF TELEVISION
The Institution of Electrical Engineers (IEE)
is to hold an international conference on
`History of Television- from early days to the
present' from 13-15 November, 1986. The
conference, which will be held at the IEE,
Savoy Place, London WC2 will commemorate the 50th anniversary. IEE tel. 01-240
1871 x222.
I am grateful to the Director of Engineering

of the BBC for agreement to publish this
article.
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Eleven years
in the ionosphere
An investigation by ionosonde of a complete cycle of
sunspots, showing by means of an original graphical
method their effect on the F2 layer variations and
maximum usable frequency.
KURT FELDMESSER
other day I had to explain the
function of the ionospheric observatory to our local contractor. The existence of the ionosphere proved a stumbling
block, but eventually his face brightened and
he commented: "You mean it's like a natural
communications satellite?" Although, of
course, this view is quite correct, it is
chronologically inverted - but then we
describe ionosondes as 'atmospheric radars'
even though radar was invented because
engineers were familiar with the techniques
of ionospheric echo sounding.
The
Like all natural resources the ionosphere
highly variable commodity whose vagaries are still the subject of continuing research world wide, about one hundred
observatories contributing to a global picture of ionospheric variation.
The generally accepted record, standardized in the literature', is a graph of apparent
echo range versus frequency, called an ionogram. The 'apparent' range is plotted on the
assumption of a constant velocity of propagation equal to the velocity of light. But
once the exploring radio pulse enters the
is a
ionosphere, it is slowed down due to the

effect of the ionization: the deeper it penetrates, the greater is the delay it experiences
and the greater the 'apparent' range.
The process is illustrated in Fig. 1. A
ground -based transmitter emits a series of
pulses at radio frequency, the transmitted
frequency being increased with each successive pulse, the repetition frequency, however, remaining constant. Common p.r.f.s.
are 50 or 100 Hz and sounding frequencies
would typically cover from 0.5 to 20 MHz,
depending on conditions in the ionosphere.
23
Ib)
(a)
Accessible from groundbased

soundings
Electron density
ECHO SOUNDING
ANALYSIS
111
(d)
1
Apparent height
IONOGRAM
Frequency
vertically directed radio pulse is reflected with a delay dependent on the effective distance to the ionospheric layer, each
radio frequency being returned at a particular electron density. The successive delays are used to form a c.r.t. display at (d); this is
recorded as an ionogram at (c) and analysed to reconstruct the electron density profile at (a).
Fig.1. A
A normal sounding sequence lasts about

one minute. The sound of an ionosonde
picked up on a radio receiver is quite
characteristic, though the signal lasts only
long enough for the ionosonde to sweep
through the passband of the receiver. Ionosondes are thus no great source of interference.
As the sounding frequency increases, the
transmitted pulse penetrates each ionospheric layer in turn until the so-called
critical frequency of the F2 layer is reached.
All higher sounding frequencies are not
reflected but pass out into space. By plotting
the delay of each returned echo with respect
to the corresponding instant of transmission
y!,1,
11
,'1.
!t
tIl
"
'
the ionogram is obtained. Mathematical

analysis then allows the true height profile of
electron density to be derived.
The graphs are, of course, plotted automatically nowadays, the techniques having
kept pace with the advance of technology,
from the manual in the early thirties to the
automatic analogue, to the computer compatible digital with synthesized frequency stepping, producing a database extending
over 55 years.
The equipment currently in use in the
ionospheric
D signeobserdabory at Slough is
shown in Fig.2. Designed by the University
sholown
of Lowell'` it is a totally programmable
instrument, every sounding parameter
being under program control.
Several typical ionograms are shown in
24
1t
MLRy`
(+l}",
l'
II
Fig.7. Eleven year chronagram cycle, with daily sunsport number graphs.
Fig. 3. They illustrate the great variability of

the ionosphere and the consequent need for
experience and a measure of skill in the
interpretation of records. Although the F2
layer is the most useful for long-distance
communication, as can be seen from Fig.4,
of the three recorded layers (E,F1 and F2), it
is the least predictable; a feature which gives
amateur radio one of its challenges and the
professional still obliged to use the ionosphere his perennial problems.
This article presents a method of visualizing the F2 layer variations, using a graphical
method published a few years ago3. The
method proved so extremely useful that I
decided to call the resulting diagram a
`chronogram'. It is basically a graph of the 24
hours as ordinate versus the 365 days as
abscissa with the parameter under investigation plotted as one of a sequence of colours
much like a contour map. The colours follow
the resistor colour code in megahertz steps
as far as 8 MHz, modified thereafter to give
another sequence up to 17 MHz (the highest
echo frequency ever recorded at Slough).
Although 1 MHz steps may appear crude, if
we plot hour to hour variations, the changes
can easily exceed 2 MHz.

The chronagram has the basic shape of the
sunrise and sunset graph of Fig.5. If the F2
layer were totally controlled by solar illumination it would simply have the shape of
that figure. The parameter represented in
the present chronagrams is the intensity of F
layer ionization as measured by the highest
vertically incident - frequency of radio pulse
returned as an ordinary ray echo; the critical
frequency. This can readily convert to the
maximum usable frequency.
It is the departure from the basic shape of
the sunrise/sunset graph that throws much
light on the nature of the F2 layer. The curve
of sunrise is outlined well enough by the
sudden increase of ionization at F2 layer
dawn (about two hours before that at sea level).
The level of ionization persists well after
sunset. However, it does so variably and is
frequently correlated to sunspot number.
Although not measured by normal ionosondes directly, we do know from other
measurements that, like the E and Fl layers,
the D layer (the lowest layer of ionization highly absorbing to h.f. waves) de -ionizes
after sunset. Thus h.f. signals, freed from D
region absorption, still meet an efficient
reflecting region at a respectable height
some hours after sunset, giving excellent
propagation conditions
a phenomenon
well known to short-wave listeners.
In the small hours (or a little earlier
during sunspot minimum) the F2 region
ionization begins to decay, seen as a decrease
in critical frequency and reaching its lowest
value just before dawn. In mid -latitude
winter the short days do not allow a prolonged energy input to the ionosphere and
so the lowest values of ionization are seen
during winter nights. As we near the spring
equinox the daytime ionization tends to a
maximum and persists more and more into
the night. With the approach of summer two
new factors make themselves felt. Firstly,
during the height of summer (about six
weeks around mid -summer in southern
.y
pf "',7
f9
, lPi
rp
i`:
3114111111111M.
""r't
-1
6
Mum:
,,
.LxJ
ijw''I.M
wii.
La.
1dY
y:ipere4e+fir,i
lr).
v1,,
l,
25
Modern ionospheric observation

equipment at the Rutherford Appleton
Laboratory at Slough.
Fig.2.
'
:,. .......
..
..:;
140
140
120
100
80
60
40
20
o
1610
1620
1630
1640
1650
1660
1670
1680
1890
1700
1710
1720
o
1730
160
160
140
140
120
120
100
100
80
80
60
60
40
40
20
20
1730
1750
1740
1760
1770
1780
1790
1800
1810
1820
1830
1840
1850
200
180
180
r---
160
140
120
100
n VIM 7
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11
MI
20
1850
.I,
o
1860
1870
1880
1890
e,
1900
.
1910
1.
Ivv
1920
1930
160
140
120
100
II
W'
I
1940
80
60
II
40
I,
1950
20
o
1960
1970
Fig.6. Annual mean sunspot numbers over 375 years. Comparison with Fig.4 suggests that
solar activity and therefore ionospheric propagation could yet have a few surprises in
Fig.3. Representative sonograms. The splitting of the trace (seen especially in the F
region) is due to double refraction in the
store.
presence of the earth's magnetic field.
26
FINAL 21.011011401111112 MEAN
N:LATIY[ SUNSPOT
IT
WHEN
\A,\j
r'
49
MONDN4T 14EA NOON CNTKAL FREQUENCIES AT SLOUGH
Vv
`/
\
"
"
J"
P,
useful layer for communications is the
F2,
sunlight
at 300km
" Ns.v..vlv;
,s.:
1107
,1
^,
,.,,J,,
10
ti^
u
IeTI
Summer maximum-
300x'
declining
IS
100
1.,
but its short-term variations make it the least predictable.
Continuous
I
,
f`'`.'
YEAR
24
Aj`,I,
VVWV
IKI
Fig.4. The most
100
200
fr
n.v
ITT,
-evening
F2
level
declining
18
Spring
Autumn
maximum
doy
maximum
-day
Strong F1 layer
12
Minimum
0
00
Fig.5.
High sunspot number
maxima
January '-
February
March
April
May
June
July
August
September October
November
December
layer variation with solar illumination - the basic shape of a chronagram in the absence of other influences.
England) the ionosphere remains in constant illumination throughout the 24 hours

- resulting in a more or less constant level of
ionization, depending on sunspot number.
Secondly, the F1 layer becomes more and
more marked. It has been shown' that the
total electron content of the ionosphere
varies much more slowly than the electron
density of the individual layers. Whilst
broadly speaking, electron content modifies
the apparent height of the layer as the pulse
passes through the plasma, the local density
determines the critical frequency.
The F1 layer, being controlled by intensity
of illumination as measured by the height of
the sun above the horizon, ionizes increasingly with the rising sun and behaves as
if it derived its free electrons at the expense
of the F2 layer, which in mid -summer rarely
achieves the levels of ionization of spring or
autumn when again the Fl layer is less
intense. This can also be seen in summer on
a smaller scale, where on cessation of the Fl
layer in late afternoon, there appears a
sudden brief increase in the F2 layer ioniza-
tion before its settles down to the evening

values.
To the communicator the presence of the
Fl layer with its highest critical frequency at
about 5 MHz puts a limiting value on the
highest usable frequency well below what he
could reasonably expect from the F2 layer.
Days when the Fl layer dominates the
ionosphere curtail the shortwave spectrum
drastically and since everybody has to employ lower frequencies, cause congestion.
Fortunately, such days rarely persist for
more than three or four consecutively and
they stand out clearly on the chronagrams.
As autumn approaches and the Fl layer
weakens, the F2 layer reaches a second
maximum of ionization, generally a little
after the equinox. These equinocial maxima
are particularly interesting since they are a
ready pointer to solar activity. If, for instance, the spring maximum following the
autumn maximum exceeds the latter then
solar activity is on the increase and if lower
than the one in autumn then solar activity is
on the decline.
The sequence of eleven chronagrams

(Fig.7) of F2 layer critical frequency plotted
for the years 1973 to 1983 illustrates the
changes in F2 layer ionization. The graphs of
daily sunspot number plotted to the same
base demonstrate the manner in which the
ionization intensity follows changes in sunspot number.
Sometimes the correlation is very evident,
at other times perhaps less so. It is this factor
as well as the diurnal and seasonal variations
that have bedevilled statistical attempts to
correlate sunspot number and ionization
intensity. However, examination of the
chronagrams will amply repay the time
spent, by revealing many relationships that
can be applied in the study of F2 layer
propagation. There are years in the sunspot
cycle when correlation with sunspot number
is clearly very good (e.g. 1973 and 1974), and
during any year in the period around the
equinoxes. On the other hand in the summer
of solar maximum years correlation is best
found after sunset, perhaps because the high
general level of ionization tends to obscure
27
atmosphere via the polar regions, hence the

'northern lights' and only then does their
effect penetrate to mid and lower latitudes.
An ionospheric disturbance observed in
the north of Scotland may take twelve to
twenty four hours to affect the ionosphere in
the south of England and generally with
considerably less severity. In the polar regions, on the other hand, severe communication blackouts occur under these
conditions, affecting all signals traversing
the Arctic circle.
The advent of satellite links has tended to
obscure the existence of large sections of
users of traditional h.f. radio, even in the
cognizance of the professional engineer.
Because INMARSAT exists, it is assumed to
be in general use, or just about to be. In fact,
only a fraction of the world's shipping is so
equipped and there are some problems for
the smaller vessel. The cost of about 20,000
for an installation has to be justified, whilst
fitting a 200 kg stabilized platform at the
highest point of the vessel poses problems of
stability. Oddly enough, though, the fitting
of such installations to the 'motherships' of
fishing fleets has proved very popular with,
for instance, Japanese ships fishing off Newfoundland, by providing good quality voice links with Japan which are difficult to
achieve by h.f. radio for the reasons given
Fig.8. A coronal 'hole', pictured by Dr
Golub. (Science Photo Library)
above.
The boost to crew morale is an important
selling point and so is the secure com-
munication provided in the traditionally

secretive fishing industry. On the other
hand, the ionosphere is free and there are
few problems, either structural or financial,
with the use of h.f. equipment. Only the
expertise required to use the ionosphere
effectively presents a major obstacle. It is
hoped that this article has helped to dispel
some of the mystery. Much work in many
quarters is directed towards that end and the
author readily acknowledges the help received from colleagues over the years.
However the opinions expressed are the
author's own and do not necessarily represent any official view.
Fig.9. Solar corona taken by a ground -based telescope during the total eclipse of March 7,
Kurt Feldmesser recently retired from the

Science Research Council, where for the last
fourteen years he has been concerned with
ionospheric observation at Slough and
South Uist for the Rutherford Laboratory.
1970 (National Center for Atmospheric Research USA/Science Photo Library).

the variation in energy input until the sun is
low in the sky. I feel one ought to bear in
mind that sunspot number is only the most
readily observable indication of solar activity. It is because of this observability that we
have sunspot records extending for 300 years
since Galileo's time, in fact (Fig.6) with
sporadic reports of non-instrumental sightings even much earlier.
Which feature of solar surface activity is
connected with terrestrial effects is the
subject of intense research, nowadays greatly aided by numerous satellites and orbiting
laboratories. Some of the candidates for
investigation regarding effects on the ionosphere are, beside sunspots, foci of X-ray
emission, coronal 'holes' (Fig.8) and the
corona itself (Fig.9) with its exceedingly
28
high plasma temperature. Direct UV and

X-ray emission reaches the earth simultaneously with visually observable changes
(as from a solar flare during a Dellinger fade
out), but charged particles emitted during
such an event will.reach the Earth some time
after the emitting region has passed the solar
meridian, the delay being a function of the
rather variable velocity of emission.
During a solar flare shown in the heading
picture and following the Dellinger fade
due to intense ionization of the D region
over all the illuminated half of the earth's
surface
these particles reach the ionosphere several hours later, producing yet
further disruption of radio signals. Since the
particles travelling earthwards are electrically charged, they can only enter our
References
1 U.R.S.I. Handbook of lonogram Interpretation
and Reduction. W.R. Piggott and K. Rawer. World
Data Center A, N.O.A.A., Boulder, Colorado.
2 "The Universal Digital lonosonde". K. Bibl and
B.W. Reinisch, Radio Science, 13, pp. 519-530
(1978).
3 "Sunspots, the ionosphere and h.f. propagation", Wireless World. Feb. 1979.
4 Journal of Geophysical Research 56, No 4. Dec.
1951.
Acknowledgements
Fig.4. Rutherford Appleton Laboratory, -Chilton,
Didcot, Oxon.
Fig.6. "A New Sun" The Solar Results from Skylab.
John A. Eddy Ed. Rein Ise, N.A.S.A. Washington
D.C. 1979.
Fig.9. National Center for Atmospheric Research,

U.S.A./Science Photo Library.
Fig.8. Dr L. Golub/Science Photo Library.
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29
Heatsink simulation on a
personal computer
Take a cool look at your next heatsinking problem with this
versatile analysis technique

BY J M HOWELL
Distributors' catalogues nowadays

offer a bewildering variety of heat sinks, ranging from tiny clips similar
in size to the device on which they are fitted,
to massive aluminium extrusions with provision for forced air cooling. The material,
shape and surface finish are chosen to
conduct heat away from the attached devices
and dissipate it to the surroundings in an
efficient manner. Selecting such a component is usually a simple task: the maximum
acceptable thermal resistance is calculated
by dividing the heat load in watts by the
temperature gradient in degrees C, and a
heatsink with a similar or slightly lower
resistance can be picked out of the catalogue.
This approach is adequate when the designer feels a stock item is satisfactory but it is
often worth consideringalternative methods
of heat removal. A frequent possibility is to
use the metal case of the equipment, though
any metal component has potential as a
heatsink. Unfortunately the average equipment enclosure is not designed with heat
transfer in mind, and thermal resistance is
not usually quoted in the specification. The
properties of a thin metal sheet are substantially different from a professionally designed heatsink of similar area.
Although the only certain way of assessing
a heatsink system may be to actually manufacture and test it, advantage may be taken of
modern technology to narrow the range of
possibilities. This article develops a mathematical model of a simple plate heatsink and
shows how a personal computer may be used
to solve the resulting set of equations.
MATHEMATICAL THEORY OF HEAT
TRANSFER
Of the three ways in which heat is transferred only conduction is relevant within the
bulk of the metal heatsink, and the other two
are responsible for the removal of heat from
the surface. The quantity of heat transferred
is directly related to the temperatures of the
components and their physical properties.

The fundamental relationship that describes the steady-state temperature distribution T(x,y) across a uniformly conducting plate, Fig.1, is the Laplace equation:
but they do not have a known analytical

solution, since the loss term H is a nonlinear function of temperature. However, a
numerical solution is still possible if we
divide the plate up into a rectangular grid
and derive the corresponding set of finite difference equations.
This is equivalent to assuming that the
plate is actually built up from a number of
perfectly conductive tiles which have been
Fg.l. Mathematical model is based on a thin joined at their narrow edges with imperfectplate which gains heat from devices at ly conducting material, Fig.2. As the tiles
several points on its surface. This heat is become smaller, the finite -difference soludistributed throughout the plate by conduction approaches the true one. For a section
tion and removed by radiation and convec- which does not lie on the edge of the plate:
tion.
30
where
nx
bi
hx
HITiil
T
Numerical method reats the plate as a

patchwork of small tiles joined by imperfectly conducting glue. Smaller tiles give greater
accuracy but require more computer time
Fig.2.
to solve.
This is modified in our case by the presence of one or more heat sources W(x,y) and
the effect of heat lost to the surroundings by
convection and conduction, H(x,y,T). The
conductivity of the metal, km, is also intro
duced now to give
k`zlaxz+aZZ]+W-H=0
Y
As no heat is lost from the narrow edges of
the plate the boundary conditions along all
edges will be
aTI
axy
azT+
a2T=0.
ax
ay
Tit,1
Wi j
=aT1
aT
ay
x=0ax
= aT
y=ymax
ay x=xxmax
=0
These equtions constitute a complete

mathematical description of the problem,
hx=kmzAy/ix and hy=kOx/Dy.
The boundary conditions are introduced by

modifying the above equation for sections
which lie on the edges, to remove the terms
which represent the temperature difference
beyond the plate edges.
The Stefan -Boltzmann law, which relates
the temperature of a surface to the radiated
heat loss, can be used to find the corresponding part of term H. The convective loss part
is more difficult to determine, since it
depends on the size, attitude and shape of
the surface. An empirical relationship for
small rectangular vertical plates has been
chosen as the most useful case:
H(T)= lk,((T+Tamb+273)4 -(Tamb+273)')+
kc(T+Tamb) k l ECixOy.
NUMERICAL SOLUTION OF THE

EQUATION SET
Each grid point of the plate has one equation
associated with it, and the temperature
profile is the simultaneous solution of all
these equations. The distribution of unknown variables (temperatures) within the
equations and the presence of nonlinear
terms forces us to adopt an iterative scheme.
In this, we guess a temperature distribution
and gradually improve on it until all the
equations are satisfied. Naturally the guess
and improvements are the result of some
fairly complex computations, which are derived next.
Rewriting the equation set in matrix form,
at the solution
At+w-h(t)=0,a
and at a point dt away from it,
A(t+dt)+w-h(t+dt)=e.
A is a matrix with positive constant
terms hX and by appearing symmetrically
about the leading diagonal and the negative
sums of these terms along this diagonal, and
t, w and h are the vector forms of the
respective terms in the earlier paragraph.
Taking the first term of the Taylor expansin of h and subtracting the two equations
we obtain the relaxation of the iteration
scheme. This will determine the step dt
which should reduce e to zero:
Here,
dt=
(A
To solve this equation, the matrix (known as

the Jacobian) does not need to be inverted
but still needs to be factorized, that is,
reduced to lower and upper triangular factors. This is a lengthy process which, if
repeated at each iteration, would add greatly
to the task. Fortunately, the only term which
changes from one iteration to the next is the
derivative of h, and in practice a small error
in its value makes little difference. Consequently, a good estimate at the start will
suffice for all subsequent iterations and the
same factorization.can be used repeatedly.
The initial guess for the temperature
profile is found by assuming the whole plate

is perfectly conducting and applying a crude
STEADY STATE HEATSINK SIMULATION
1
ALUMINIUM
COPPER
BRASS
MILD STEEL
SELECT MATERIAL (1-4) ? 3

EXPOSED SURFACE RATIO (0.5-4)
ENTER 0 TO FINISH
HEAT INPUT (WATTS)
GRID LOCATION (1HEAT INPUT (WATTS)
1.2
11.92
.1-
51
substitution algorithm. The derivative term

then follows from the change in H for a unit
SYMBOLS IN EQUATIONS
increase in T.
PLATE DIMENSIONS
LONG EDGE (MM) 7 262
SHORT EDGE (MM) 7 114
MATERIAL THICKNESS (MM)
Factorising Jacobian
Solving Equation Set
At iteration
1
Error
At iteration 2 Error
At iteration
5
Error
PROGRAM DESCRIPTION
.9
33.1598
1.80991
T = .181643
T = 2.01621E-02
T = 2.48715E-03
in
in
in
in
in
T =
T =

BRASS HEATSINK IN. AIR AT 25
SIZE = 262 BY 114 BY .9 MM
WEIGHT = 223.114 GRAMS
DEG C
HEAT SOURCES (WATTS)

11.92
o .
o
o
o
o
o
o
o
o
TEMPERATURE DISTRIBUTION (DEG C)

114.62
77.94
63.87
64.97
57.38
52.6
45.74
44.04
42.69
37.34
36.93
36.57
34.02
33.9
33.78
Break in 1480
The solution method described above involves a great many repetitive calculations,
and is only practical when programmed into
a suitable machine. To this end, a program
has been written in Microsoft Basic for use
on a personal computer (actually an IBM
PC), but special care has been taken to avoid
machine -specific features, so it should run
with little or no modification on a wide range
of machines.
The program starts by setting up the data
structures and constants it will need later.
The most important of these is the size of the
grid used to build the set of finite -difference
equations, preset by Nx.NY to 3 by There is
nothing to stop this being altered except that
the computation time increases as the cube
of the product of NX and NY. The values above
will give computation times of around half a
minute on an IBM PC or similar.
The next part of the program is concerned
with reading and validating the problem by
asking the user a series of simple questions.
Matrix of heat transfer coefficients
hdly
dt
Relaxation step
Exposed surface
Vector of residual errors
i,j
Grid
indices
in
residual error
t;
in t
ratio
in
equations
along short and long
edges
Heat loss from
unit surface area
Vector of surface heat losses from

each grid point
Coefficient of convective heat loss
per unit area
km
Heat conduction coefficient
of plate
material
Coefficient of radiative heat loss per
k,
wit area
nx,nY
Number of grid
points
in x
and y
Directions
T(x,y)
5.
Temperature above ambient, deg C

Vector of temperature profile
W(x,y)
Heat inputper
Vector of heat sources to each grid
unit surface area
point
x,y
x.Ay
Positions along short
and long edges

and long
Grid spacing along short
edges
z
plate thickness
31
Reporting of errors by the program has

deliberately been kept to a minimum to
reduce program length but this is easily
remedied.
Any number of heat sources may be
specified in any order. The answers should
be self-evident apart from the ÈXPOSED SURFACE
RATIO'. This parameter enables the user to
allow for the effect of surface finish and
exposure. A single thermally black surface is
treated as 1.0, a heavily finned surface would
be around 2.0, and a highly polished metal
surface, 0.5. If both surfaces of the plate are
exposed, the ratio should be doubled.
Once the data has been collected the
numerical algorithm can begin. The solution method described above has been implemented, and to speed up the process,
given an understanding of popular Basic
interpreters, a number of intermediate variables have been introduced. REM statements
in the listing explain the principal sections.
A subroutine is used to find the heat loss H
on one grid rectangle at temperature T.
Step-by-step progress reports are included
for verification purposes and can be deleted
if required. The algorithm terminates when
a weighted average of the step vector DT falls
below 0.02C.
Finally a summary of the problem and the
table of temperatures at the centre of each
grid point are printed. The weight is included as a convenient check that the plate
dimensions are reasonable.
PROGRAM VERIFICATION
To check the results of the simulation
program a practical test was conducted. The
conditions were chosen to exaggerate the
known weaknesses of the solution method,
so it may be regarded as an extreme case.
A bright, unpolished brass plate was
marked off with the appropriate grid and a
power transistor mounted in the centre of a
corner rectangle. Fourteen small transistors

were press -fitted into holes at the centre of
each remaining rectangle for use as temperature sensors, and a 15th fitted to one side of
the power transistor. This equipment was
run for 30 minutes under the specified
conditions to reach a steady state and the
temperature distribution measured. The results are shown in Table 1.
Table 1. Temperature profiles deg
50
41
52
52
43
43
39
39
40
Horizontal plate
58
62
68
46
38
39
38
35
35
35
Vertical plate
64
78
53
57
43
44
65
46
34
34
34
Simulation program
114
37
37
37
81
60
66
104
74
64
80
98
63
47
46
Table 2. Test conditions

Plate material: 70/30 plain brass sheet
Plate dimensions: 0.9 by 262 by 114mm
Heat sources: 11.9 watts into grid point. 1,1
Exposed surface ratio:12
Apart from the hottest corner, the vertical

plate temperatures show fair agreement
with the simulation. The horizontal attitude
was tried to determine the validity of the
32
10 REM HEATSINK MODELLING PROGRAM

20 REM J.M.HOWELL JUNE 1986
30 DEF FNA(X)-INT(X'100)/100
40 NX=3:NY=5:N=NX'NY
50 TAMB=25:KR=5.14E-14:KC1.98E-06
60 DIM W(N),T(N),A(N,N),E(N),DT(N)
70 RESTORE
80 DATA "ALUMINIUM",0.230,2.7,"COPPER",0.377,8.9
90 DATA "BRASS",0.112,8.3,"MILD STEEL",0.052,7.8
100 GOSUB 1490.
110 POR 1.1 TO 4
120 READ M$,X,X
130 PRINT I;". ";M$
140 NEXT I
150 PRINT
;M
160 INPUT "SELECT MATERIAL (1-4)
170 IF M<1 OR M>4 THEN GOTO 160
180 INPUT "EXPOSED SURFACE RATIO (0.5-4) ";E
190 IF E'.5 OR E>4 THEN GOTO 180.
200 WI=0
210 PRINT:PRINT "ENTER 0 TO FINISH"
220 INPUT "HEAT INPUT (WATTS) ";W
230 IF W<=0 THEN GOTO 340
240
250
260
270
280
290
300
310
320
330
340
350
360
370
PRINT
INPUT
IF
"GRID LOCATION
(1-";NX;",1-";NY:")
",
I,J
I<1
OR
I>NX OR J<1 OR J>NY THEN GOTO 310
KI+J'NX-NX
W(K)=W(K)+W
WIWI+W
GOTO 320
PRINT I;",";J;" IS BEYOND EDGE OF PLATE"
PRINT
GOTO 220
GOSUB 1490
PRINT "PLATE DIMENSIONS"
INPUT "LONG EDGE (MM) ";Y
INPUT "SHORT EDGE (MM) ";X
380 INPUT "MATERIAL THICKNESS (MM) ";Z
390 PRINT
400 IF Z>0 AND X>Z AND Y>X THEN GOTO 430
410 PRINT 'PLEASE ENTER IN CORRECT ORDER"
420 GOTO 360
430 REM Determine Heat Transfer Properties
440 RESTORE
450 FOR 1.1 TO M
460 READ M$,KM,RHO
470 NEXT I
480 HXKM'Y'Z/X'NX/NY
490 HY=KM'X'Z/Y'NY/NX
500 REM Define Dissipation Coefficient constants
510 11.4=(273+TAMB)-4
520 S=X/NX'Y/NY'E
530 REM Find average plate temperature
540 T=50
550 FOR I=1 TO 5
560 GOSUB 1540
570 T=T+WI-NX'NY'H
580 NEXT I
590 REM Find slope of heat loss curve
600 GOSUB 1540
610 HO=N
620 T=T+1
630 GOSUB 1540
640 DHDT=H-HO
650 REM set up jacobian matrix
660 FOR I.1 TO NX
670 FOR J1 TO NY
680 K=I+J'NX-NX
690 AMDHDT
700 IF I>1 THEN A(K-1,K)HX:A=A+HX
710 IF I<NX THEN A(K+1,K)HX:A=A+HX
720 IF J>1 THEN A(K-NX,K).HY:A=A+HY
730 IF J<NY THEN A(K+NX,K)-HY:A-A+HY
740 A(K,K)--A
750 NEXT J
760 NEXT I
770 PRINT "Factorising Jacobian"
780 REM perform LU decomposition on jacobian
790 FOR I=1 TO N-1
empirical convection equation under such

circumstances. The discrepancy in the hot
corner is probably due to the relative position of the sensor, which lay midway between the grid centre and the plate edge.
The simulation results can of course be
used to verify the program after it has been
typed in. For this reason the screen output
for a complete run is included, and the
output from any Microsoft -type Basic should
agree very closely with this. Any deviation
indicates a typing error or some nonstandard aspect of the Basic interpreter. An
example of the latter is the BBC computer,
which executes all FOR -NEXT loops at least
once, even if the loop range is actually nil.
This introduces a bug which makes the
program take many more steps than are
needed. For correct operation in this instance an extra line is required: 1125 IF I=N THEN
COTO 1160.
800
810
820
830
840
850
860
870
880
FOR JI+1 TO N
A=-A(I,J)/A(I,I)
A(I,J)=A
POR K=I+1 TO N
A(K,J)=A(K,J)+A(K,I)'A
NEXT K
NEXT J
NEXT I
PRINT "Solving Equation Set"
890
900
910
920
930
940
950
960
L=0
REM
REM
FOR
FOR
Main iteration loop start

Find error
I=1
term
TO NX
J.1 TO NY
K=I+J'NX-NX
TTT(K)
GOSUB 1540
E=-H+W(K)
980 IF I>1 THEN E=E+HX'(T(K-1)-T)
990 IF I<NX THEN E=E+HX'(T(K+1)-T)
1000 IF Jul THEN E-E+HY'(T(K-NX)-T)
1010 IF J<NY THEN E=E+HY'(T(K+NX)-T)
1020 E(K)=E
1030 NEXT J
1040 NEXT I
1050 REM solve matrix equation for DT
1060 FOR I=1 TO N-1
1070 FOR J=I+1 TO N
1080 E(J)=E(J)+A(I,J)'E(I)
1090 NEXT J
1100 NEXT I
97.0
1110
1120
1130
1140
1150
1160
1170
.1180
1190
1200
1210
1220
1230
1240
1250
1260
1270
1280
1290
1300
1310
1320
FOR I=N TO 1 STEP -1

DT(I)=E(I)
FOR J=N TO I+1 STEP -1
DT(I) eDT(I)-DT(J)'A(J,I)
NEXT J
DT(I)=DT(I)/A(I,I)
NEXT I
REM compute norm of DT and update T
D2.0
FOR 1=1 TO N
D2=02+DT(I)'DT(I)
T(I)=T(I)-DT(I)
NEXT 1
UT=SQR(1.12/NX/NY)
REM Loop monitoring
L=L+1
PRINT "At iteration ";L;" Error in T =";01
IF DT>.02 THEN GOTO 900
REM Output Results
GOSUB 1490
PRINT MS:" HEATSINK IN AIR AT";TAMB;" DEG C"
PRINT "SIZE =";Y;"BY";X;"BY";Z;"MM"

1330 PRINT "WEIGHT =";X'Y'2'11110/1000;"CRAMS"
1340 PRINT:PRINT "HEAT SOURCES (WATTS)"
1350
1360
1370
1380
1390
1400
1410
1420
1430
1440
1450
1460
1470
1480
1490
1500
1510
1520
1530
1540
1550
FOR J=1 TO NY
FOR I.1 TO NX
PRINT TAB(I'12-11);FNA(W(I+J'NX-NX));
NEXT
PRINT
NEXT J
PRINT:PRINT "TEMPERATURE DISTRIBUTION
(DEG CI"
FOR Jet TO NY
FOR I=1 TO NX
PRINT TAB(I.12-11);FNA(T(I+J'NX-NX)+TOMB);
NEXT I
PRINT
NEXT J
STOP
REM Print title
CLS
PRINT:PRINT "STEADY STATE HEATSINK SIMULATION"

PRINT
RETURN
REM Find heat
lose H for temp rise T

A.T+TAME+273
1560 HR-KR'(AA'A'A-84)
1570 HC=KC'SQR(SQR(ABS(T+TAMB)))eT
1580 H=(HR+HC)S
1590 RETURN
structure may be analysed as
a plate of
similar thickness and area. The effect of
mounting several devices on the same heat sink can also be studied.
The results need to be tempered with a
degree of engineering judgement. For example, the individual rectangles of the grid are
assumed to be perfectly conducting, and if
an exceptionally thin or poorly conducting
plate is modelled then this assumption will
not be valid. In consequence the temperature of the centre of each hot rectangle is
appreciably higher than predicted by the
model. To overcome this problem a finer
grid must be used. A more powerful computer may then be needed, or the Basic program could be compiled, to avoid long run
times.
Despite the limitations, many will find
this program a valuable addition to their
software library.
USING THE PROGRAM

The main benefit of a program of this nature
is that a large number of possibilities can be
considered at an early stage of a project and
the non-starters eliminated without wasting

effort on them. The program has been
written for flat metal plates and if lower
accuracy can be tolerated any shape or
Dr. Howell worked as chemical and systems

engineer for various companies, and is presently control engineer at ICI, Billingham. He
gained his Ph.D. for research into optimal
control of large chemical process networks,

and has interests in electronics, computing,
and amateur radio.
LOGS AGAIN
Flushed with success at demystifying decibels, Joules
Watt has not yet finished with logarithms...
JOULES WATT
short while ago I commented upon

what might be called slovenliness,
egarding the use of decibels'.
If not slovenliness, at least loose thinking
about such matters causes confusion for the
poor student. This has become true for
novice radio amateurs as well. One confided
to me, "It struck a little fear into nearly all
the RAE class, when the mysterious dB arose
in transmitter power discussions". I hope my
short discourse earlier helped dispel some of
the mystery.
But we are not out of the wood yet,
because two colleagues took me to task with
criticisms. One said, "You got no further
towards helping anyone see the meaning of
response curves. Are the 6 dB per octave
slopes a drop-off in power gain or voltage
gain?" The other fellow suggested I too was
being a little slovenly, in that doubling the
power is not exactly 3 dB up, therefore four
times is not exactly 6 dB, and so on. He is
right, of course, but the differences are very
small, as Table 1 shows.
Much of all this argument appears to rest
on the properties of logarithms. Long gone
are the days when we slaved away looking up
columns of figures in tables for something
called the mantissa and something else
called the characteristic - or are they?
Nevertheless, it was only when we arrived at
the integral calculus that we discovered a
mysterious "irrational" number called e. As
with Tr before it, we were told that "it has an
unending, never repeating decimal part,
which arises naturally..."
It soon became obvious that logs arise
from this number e, as well as via the laws of
indices generally. A logarithmic result to the
base e is obtained when the area under a
rectangular hyperbola is sought by using the
integral
r
y=J Xx=1nx
(1)
The symbol "ln" reads "The natural logarithm of..." and is also written "loge". The
common logs to the base ten (written logo,
or just log for short from now on), cropped
up recently in the discussion of decibels'.
Log to the base 2 (loge) is seen in discussions
concerning information and communica-
tions theory.
When physical quantities, instead of pure
numbers, become involved in this kind of
calculation, trouble tends to arise. Pure
mathematicians avoid all that by claiming
that they work with pure numbers only.
Dimensions never come into things. Engineers, on the other hand, are always
talking about so many amps, volts, newtons,

watts and the question is asked as to whether
the unit is inside the symbol - or attached
separately. In other words, is the quantity R
a number complete with dimensions ohms
within it, or should it be written R ohms,
where R is a pure number?
From the integral (1) y is certainly dimensionless, because if x has dimensions, the
small bit of it, dx, has the same dimensions,
and these cancel in the ratio. But if x does
have dimensions, say watts, then the question is whether log of watts can equal a
dimensionless number? This is not a real
problem, because I have neglected the fundamental need for a constant to add on to
any integration. In this case (for example) we
can say "let x = p watts when y = 0" so that
the constant is -ln p and the complete
answer is:
TABLE 1
Usually taken as:

3dB
10log (P2/P1)
3.0103
6.0206
9.0309
6d8
9d8
10
10
10dB
64
18.0618
18dB
100
20
20d8
2.749x1011
(30 doublings)
114.3914
114d8
P2/Pl
2
Vdd
vo
y=1np
cs
and everyone is happy, as we have a pure

ratio of watts over watts again.
But this is not so for the 'quantity calculus' people 2.3.4, who argue that the
symbols of the units can be handled and
juggled just like numbers. You can square
them, divide, take logs of them. And so, as
you might expect, a fairly hot controversy
has raged over the claim to do this.
After considering these arguments, I incline towards the old view that quantities
cannot have logs taken of them - or the sine,
tangent and so on, for that matter. We can
only use ratios of same -dimensioned quantities in the arguments of the transcendental
functions. Of course, all the modernists will
label my stand as reactionary.
In practice there is no trouble, because
the measure of quantities is really a ratio in
every case. A voltmeter reading 20 volts is
really saying, "The basic unit (volt) goes into
the value being read (20 volts) 20 times. i.e.,
20 volts/volt equals 20 times." Therefore if
we take logs of a power in watts, we are really
taking cognizance of a number of times a
quantity is in a ratio to the basic unit.
Therefore 101og P is really 101 P(watts)/
watt or so many dBW.
If we are told that the comparator unit is

milliwatts, then the operation can be written
103P(milliwatts)
P(watts)
101ogmilliwatt-101og
milliwatt
dBm = (30+dBW)
Fig.1. This typical j.fet resistance -capacitance coupled amplifier stage is typical of
all such active device gain blocks, (with
appropriate attention to input and output
impedances). The unmarked components
are assumed not to affect the frequency
response. In other words, C, dominates at
the low end, while the strays can be lumped together as C. to limit the performance
atthe high end.
THE PLOT THICKENS

(at least towards the high values..)
Displaying data logarithmically to expand
the detail at the low end of the scale and
compress it at the high end enables a huge
range of information to be shown on one
sheet of graph paper. This explains why log log and log - linear graphs are so ubiquitous
in engineering reports and scientific papers.
You can get log paper in so many cycles
(decades usually) along the two axes. One
consequence is that the true origin goes off
to infinity downwards and to the left along
the axes. (Log 0 -> x).
Another reason why log plotting is so
useful is that many phenomena vary logar-
ithmically, which means many data

measurements produce straight line plots
on log- log paper. Other"laws" which would
produce curves on linear-only paper, will
produce straight line plots on log - lin paper.
Again, to overcome the "worry" about the
meaning of units along the log axes, we
33
think of the numbers as 'so many units per

unit' of the quantity, so that you are never
taking the log of anything but a pure ratio. (A
ratio is a pure number, but a rate is a
quotient of different quantities - like 'miles
per hour'.)
where
gmReq
i
rd
L
where RegrdRd+rRR
RL+ RdRL
In order to see the effect of C5 at high

frequencies, it is added in shunt to Req as
shown in Fig.2(b)
Ah=--gm
34
and
Xs=0-
But
-gmReq IS Amid
therefore:
Ah -
al
Req
This can be written
o
vi
lw
1+1w2
(b)
w2-ReqCs
The ratio of the high -frequency gain to the

mid -frequency value, is called normalization
- in this case, normalizing to the midfrequency gain as a reference. It is as though
we have set the mid value to unity, but
normalization does more than that, it removes any dimensions of the quantities in
the ratio, (although in this case, the As are
already dimensionless).
The result derived for the normalization
voltage gain is a complex number. You
probably remember such numbers have real
and imaginary parts. Because I introduced
phase shifts resulting from the circuit reactances by using the operator j, the complex
result arises naturally. It has the advantage
that when written down in the polar form,
the amplitude (or magnitude) and the phase
angle are immediately given. In the present
context, these two pieces of information tell
us all we want to know about the amount of
amplification on the one hand and the shift
in phase of the output relative to the input,
at any given frequency, on the other.
1+j
1
!COI
Va
RL
1+j Reg
Amid
where
measuring the power output of an amplifier and (with the same power meter) the
power input, we can take their ratio and thus
write down the power gain in dB. Whether
this is the available power gain, or the
transducer gain, or matched power gain and
soon, is another confusion, as it dawns upon
us that different people define power gain
differently. Nevertheless, the ratio of two
powers to give decibels is now basically
g m'``,
rd
By
Amid =v
---
Req
Req-1Xs
1+j XsXq
IT BODES WELL
simple.
The question might arise as to relative
gain over, say, the frequency band of an
amplifier. It might also be asked for in terms
of the voltage gain. But we sigh with relief
because the relative gain will be measured at
the same point (the output terminals) and
therefore across the same impedance,
assumed to be a non -reactive load for instance. This means that voltages can be
measured for the decibel levels.
All amplifiers suffer shunting -capacitance
losses as the frequency rises. These strays
cannot be eliminated, so gain falls off somewhere at the high end. Many amplifiers have
series coupling capacitors (except d.c.
amplifiers) so however large these are, eventually the gain will drop off towards the low
frequency end as the magnitude of the
reactance increases beyond the resistance
values. In other words, all amplifiers are
bandpass circuits. The bandwidth B is the
frequency interval between the "3 dB down"
points. Of course, specialized amplifiers
might depart from this simple scenario.
Baxandall tone control stages would do so,
for example. Figure 1 shows how a simple
voltage amplifier fet stage appears.
Figure 2 shows the well known equivalent
generator circuit for such a stage incorporated into the mid -frequency range, where
the capacitances have no effect; the low
frequency region, where C. dominates, but
the shunt strays do not; and at the high
frequency end where the total shunt capacitance Cs dominates, but C. does not. These
notional independent regions are the usual
assumptions made about a fairly wide -band
amplifier, but for narrow -band cases other
methods have to be used.
The mid -band voltage gain is simply the
voltage -controlled generator current multiplied by the total equivalent resistance at the
output:
Zis -1RegXs or
V1+(02
w2
/-tan-' w2
o
(d
Fig. 2.1n (a) the mid -band equivalent circuit

is shown. The 'mid -band' can be defined as
wmid= Vw1w2. At (b) is the effect of Cs
which shunts the output circuit The "3 dB

down" frequency is that at which the
magnitude of the reactance of C5 becomes
equal to ReQ. This frequency, also known as
the 'high -frequency cut off point', is denoted 0)2, where w2 is 27112. f2 is the
frequency in hertz.
The low -frequency case shown in (c) is a
little more awkward, in that Cs is in series
with RL and this is in shunt across the rest
of the resistive components. wl is the cut
off frequency at the low end and it occurs
at the frequency where the reactance of Cc
has a magnitude equal to RL summed with
the resultant of rd and Rd in parallel.
(2)
-Reggm j(RD+RL)
yo- -RDgmRL
have written this result using the rather
v.
RD+RL-jXe
1+ RD+RL
X`
out of fashion notation for amplitude A, and
X
1
angle L_ 9, but which has merit and perhaps
we should rehabilitate it a little.
ReQgml
Returning to Fig.2(c) where I show the
1+.4,-Tt
equivalent circuit for the low -frequency end,
the effect of C5 is now negligible, but that of
C. rises into prominence. The generator Where Req is the same as before.
Writing the final line for the normalized
current divides into rd and Rd in parallel as
one path, and C. in series with RL as the gain at low frequencies, we obtain:
other. I have combined the result of rd and Rd
w
in parallel as RD and, using the current
wi
divider formula, the current through RL can
1+jW1
w I7r-tanWAmid
be written down. Knowing the current
1+WZi
through the load resistor will give the
voltage across it, namely, v.
This time wi stands in for 1/(Ro+RL)CC and
is another cut-off point - the low frequency
one. These values, wi and w2, are also called
-RDgmViRL
"break" frequencies. The reason for these
V0_ RD+RL-jXc
terms becomes obvious when we get back to
logs shortly.
where
Xc=wCc
Before taking logs of the amplitude of the
low and high -frequency gain variations, I
have plotted in Fig.3 the linear amplitude
The algebra can be re -arranged to give a 1 +j versus frequency result as an instructive
term in the denominator to make it look like illustration of a direct attack. This turns out
the first result:
to be less useful than at first thought. A log I
Taking twenty times the log is no mistake as we now have the normalized voltage gain
in decibels to plot against the log of the
frequency.
If you take a look at the log equation above
with ww2 then the right-hand side
approaches log 1, which is 0. Therefore, on
the log plot there is a horizontal line at 0 dB
which corresponds to the normalized mid band value. Now consider ww2. The "1"
can be neglected now in the bracket of the
log argument:
-0707
b 06
w 04
o2
-W1=01
w2=10
o
0
10
15
System X
speedup
25
20
FREQUENCY
very lop -sided result occurs if

linear plots are attempted for frequency
response. Also such curves accord very
badly with subjective results, considering
the logarithmic response of the ear.
Fig.3.
10
12
NORMALISED ANGULAR FREQUENCY
(Ah 1
Amid/dB
=-20logw
w2
Plotting this on Fig.4 gives a straight line

with a slope of -20 units for every factor of
ten times w increase. The units here, of
course, are decibels. The two asymptotes
have a common point at w=w2. Therefore on
the log plot, an approximation to the amplifier response has been obtained with a sharp
"break" point at w2. You can see that in
practice, at w=w2, the argument of the
logarithm is V2, and the actual response is
down 3 dB at this point. When the frequency
is at twice the cut off value, then the actual
response is 201ogV5 = 7 dB down. This is
one decibel lower than the asymptote at the
2w2 point. Similarly, at half w2 the response
is again one dB lower. This means we can
sketch the actual smooth response curve
quite accurately. The last notable comment
to make is that the slope of the response
curve approaches "6 dB per octave". We now
have all the 'jargon' commonly met in these
discussions. The "3 dB down" point; "6 dB
per octave" or "20 db per decade"; "break
point" and so on.
This kind of response is typical of a
"one -pole system", where the pole is at the
frequency which makes the denominator
zero in equation 6. The lower break point is
obtained in the same way, except that there
is a "zero" in the numerator (see equation 3)
as well as a pole at wi. I will "leave it as an
exercise for the student" as the saying goes,
to sketch the Bode plot at the low end. You
should get a curve such as that in Fig.5. I
have also left out of the discussion the plot of
the phase angle from the tan -1 information.
For completeness this should be done and
readers can do it themselves, if interested.
I have mentioned poles and zeros. They
have arisen naturally in logarithmic discussions of response curves via Bode plots. But
any further look at them is a whole topic, and
suffice it must be for now to hope that I have
answered my critic's point about "what does
it mean about 3 dB down on response
curves?" and in doing so might have pointed
up for you a few of the mysteries of these
curves...
The benefits of digital switching came
to a further 3500 telephones in the

City of London when this System X
exchange went into service at the end of
August.
A panel from the 600 exchange is demonstrated here by Ian Valiance, British Telecom's chief of operations. The new equipment forms one of two exchanges housed at
Wood Street and it replaces two floors of
o
39 -year -old Strowger electromechanical
-1dB
6dB/atnve
-3dB
switches. The other exchange, 726, will be
commissioned shortly.
All telephone users should benefit from an
3 -10
improvement in the quality of service. But
System X offers many new features to
suitably -equipped customers, such as direct
digital interfacing.
BT's System X programme has been lagging some 15 months behind schedule because of supply problems. But over 70
10
100
a1
System X local exchanges are now in operaNORMALISED ANGULAR FREQUENCY
tion nationwide and new digital exchanges
are entering service at the rate of one every
Fig.5. A similar plot at the low -frequency
working day. By the end of the decade, half
end of an amplifier's response gives simithe BT network and all its trunk circuits will
lar information just as conveniently.
be digital.
Even rural communities are gaining the
log plot (on log - lin paper, because decibels
facilities
of System X with the introduction
are used on the vertical axis) is much more
of the smaller UXD5 digital exchange: some
fruitful. The log plots turn out to be "piece 200 are now in use and a further 300 are
wise linear" and they are all associated with
being installed or are on order. But seven
the name Hendrik Bodes. These Bode plots
million subscribers will remain on analogue
are a very quick way of seeing the frequency
TXE4 systems.
characteristics of an amplifier, once the
The switch -over at Wood Street took place
have
been
derived
complex gain equations
at lunch-time on a Friday, which is reckoned
References
and the logs taken.
to be the quietest time in the City. With
1 'Joules Watt', 'Ringing the Changes on Bels'
Consider the high -frequency end of the
military precision a squad of exchange staff
amplifier response I have discussed above. Electronics Wireless World, September 1986
2 J.E. Boggs, 'The Logarithm of "Ten Apples"
completed the conversion in a two-minute
We take common logs of the normalized
lour, Chem. Edn. 35, p30, January 1958
operation: tugging on handfuls of string
gain expression (equation 2):
3 G.N. Copley, (Lett.) Jour. Chem.Edn. 35, p366,
festooning the distribution frame, they dis1958
connected the old system by pulling out
Phiand
Dimensions'
z
Guggenheim,
'Units
4 E.A.
thousands of tiny plastic wedges. On a
1
-2--201og (1+W2 losophical Magazine, 33, p479, July 1942.
201og- =20108
Amid
further command, with more string -pulling
5 H.W. Bode "Network Analysis and Feedh-'1+W
they switched in the new.
1957.
Amplifier Design" Van Nostrand,
such as that shown here

for the high -frequency response, is a very
convenient way of using a logarithmic
presentation to give a rapid overview of
data quickly.
Fig.4. A Bode plot
INI
35
CIRCUIT IDEAS
Clock
Clock
Input
TOUCH -OPERATED SWITCH
8254 out
Resistive and capacitive touch switches can

give problems. When distorted by only light
OutputOJ
PR
(I
CLR
Monostahle
7474
period
CK
Input
Output
FREQUENCY DISCRIMINATOR
Analogue techniques like the charge-pump
and level detector are usually used for
frequency discrimination. These require a
d -to-a converter to make them digitally
programmable and suffer from a limited
operating range.
Digital discriminators count pulses and
then periodically compare the count with a
reference, giving a large threshold range but
requiring an amount of software that rises
with increasing input or reference frequency.
This discriminator uses a programmable
timer configured as a monostable device (the
Intel 8254 in mode 1) to provide an above/
below indication. Extra software is not re-
quired and the threshold is programmable

over a 1:216 range.
Input leading edges trigger the monostable device. If input is slower than the
monostable's timing, a high level'is IatChed
in the 7474 and if input is faster a low level is
latched.
Pulse widths from 1 to 216 multiples of the
input clock can be programmed. Other
timers in the same i.c. package can be used
to generate the clock. This provides a very
wide range of threshold frequencies.
Adrian Godwin
finger pressure, the piezo-electric transducer produces quite a high signal which can
be passed through a Schmitt trigger to give a
clean switched output.
I used a 23-by-0.3mm piezo-electric buzzer element. To completely isolate the transducer, it may be glued to the inside of a
plastic container. Turning the transducer
over reverses the switch action.
G. Sullivan
Redditch
Worcestershire
Bedford
[Ake
~
rill ~82 n
10k
22k
82n
~560n
~560n
1728n2100
17-6-8n2
10k
C1
- 100
10
2-10p
1k
_56n
1k -.10k
.-270p
Frequency range
h_
10k -100k
*15V
270p
le 5n6
4p7
AD534JH
Low leakage
5n6~111-1n
2p
25k
2k2
LM 318N
Frequency
16V
118
560p
560p
IC2
\100p /
2p
Gain
LM318N
Ov
'5v
Error amplifier
Aisin2tupt10
4p7
10k
Jk
107
AD534JH
8
22k
LM318N
9k1
LOUT
21
Asinwor
X1
ICS
10
AD534JH
L
B
X2
OUT
Z1
s
[C6
Y1
Level
12
22
-Vs
gain match
-15V
-15V
OV
2k2
Multiplier
S.F.
15
4k7
X1
10
SF
OV
Re rente
A cos Wot
A2 cos?
10
ubt
,CIRCUIT IDEAS
VOLTAGE -CONTROLLED
STATE -VARIABLE FILTER
There is a lack of a combination of transconductance amplifier and voltage op -amp on
one chip. An application for such an i.c. is
this voltage-controlled filter shown using
discrete components.
Compared with widely used switched capacitor networks, this design has a wider
dynamic range, higher upper frequency and
2B
v,t
(a)
Vin
out
(b)
Vin
R1
0-^,"\i`
gives no errors due to clock feedthrough and
SINE WAVES WITH FAST AMPLITUDE STABILIZATION

Output of this oscillator stabilizes very rapidly because the feedback signal requires no
filtering. Any ripple fed back is due to
multiplier non-linearities, integrator

component mismatch, offsets and op -amp
open -loop gain limitations.
Circuits IC1_3 form a quadrature oscillator
similar to the one presented by Filanovsky et
al. Multipliers IC5,6 square the output; ideally, the summed output contains no ripple
(cos2x+sin2x=1). This output is compared
with the reference by IC7 to produce an error
signal for controlling gain of IC8.
With frequency set to 1kHz and output at
maximum, adjust the gain -match potentiometer for minimum ripple at output of IC7.
Set the gain -adjust potentiometer so that
output of IC7 is closest to OV. The level
potentiometer is set to give 5V r.m.s. output
and C1 is adjusted to give the flattest fre-
quency response to 100kHz.

Output amplitude is up to 5V r.m.s. and
amplitude variation with frequency is within
0.3dB using ganged potentiometers matched to better than 1%. Distortion is about
0.2% at 1kHz.
Decoupling is needed and stray capacitance should be avoided, particularly around
the LM318 inputs and outputs.
Paul W. Chisholm
Maidenhead
Berkshire
Reading
Applications of operational amplifiers, J.G.
Graeme, McGraw-Hill.
Fast amplitude stabilization of an RC oscillator,
I.M. Filanovsky et al, Wireless World, July 1982,
pp. 52,53.
aliasing.
Output voltage of the voltage -controlled
op -amp, Vx, is given by V;,,/F where F, the
scaling factor, is 2VTRr/ARL. Voltage V, is
26m V and A is 1 +R/RA.
Integrator output voltage is given by
Vou1=
-(V/F)(1/SCRN,).
The resistor feeding the integrator inverting

input may be seen as a linear voltage -
controlled resistance.
With this integrator, shown schematically, the Kerwin-Huelsman-Newcomb 'state variable second -order active filter with three
op -amps may be altered to make a voltage programmable filter as shown in the third
diagram.
Resonance frequency too and Q factor of
this filter are given by
Vc/F
W0
and
Q= VR4R3
R1
+15V
Level range
Any value of resonance frequency can be set

using control voltage V, and R1 alone deter-
27k
x01
Level
LF351N
Low
2k7
a0.01
LF351N
1N914
0-SVrms
-I
I
`100p'
x0001
16V
270
100k
10k
1M
22k
30
Leakage
mines the Q factor.

Grain of various filter types is R2/VR3R4
for band-pass, R2/R3 for low pass and R2/R4
for high pass. Bandpass operation gives
negative output voltage; otherwise output
voltage is positive.
Kamil Kraus
Rokycany
Czechoslovakia
37
CIRCUIT IDEAS
SPEECH CONTROL FOR THE SPO-256
By replacing the usual 3.12MHz crystal
clock with a v.c.o., four programmable levels

of inflexion and manual pitch control can be
added to most speech processor circuits
using the SPO-256AL2 chip.
As the 256 only holds 64 allophones it only
has 64 memory locations and therefore only
needs six address/data lines (D0_5). Lines D6,7
can control a two-bit d -to-a converter, output of which feeds the LS124 v.c.o. through
an inflexion -depth potentiometer. This gives
four inflexion levels. Pitch range is set on a
second potentiometer.
Mel Saunders
Leicester
5V
20
15
11
16
4
0
T22P
To SPO-256
7
100k
Latch
8
74LS37
13
Pitch range
9
1
12
Infl50kexion
14
15
depth
1606
17
p7
1901
18
ToSPO-256
clock input
100k
2
47k
11
X22
10
tant.
10k
Port
WRITE
SWITCHING SERVO AMPLIFIER USING INTEGRATION

In radio control and robotics, so called
digital servos are normally used because
they are readily available and give good
performance not easily matched by simple
analogue servos.
This improved analogue servo amplifier is
simple, yet it performs as well as the digital
servo and allows deadband and drive -pulse
width adjustment for fine tuning. Output
switches. The trick is to combine an inte-
grating gain stage with a symmetrical

double -trigger output stage.
With a TL062 error amplifier, standby
current is about 2.5mA, most of which flows
through the servo potentiometer. By increasing the value of R9, supply voltages down to
about 2.4V can be used. The ratio of R1:R2
sets the dead band.
Error measurement is done during the
motor -off period so the circuit is noise resistant.
J.M. Piednoir
Le Rainey
+SV
"9
'/V
91k
cl
2N6562
iZzn
2
330
3M3
R1
5k
+5V
R3
2 N 3904
R4
6k8
yz
TL062
10k
orLM358
--51/
1R
2N3906
125V
Input
depending kI
OV
2N6560
470
throw
-SV
Mechanical feedback
Error voltage change
+0.62V
+0.15V
0V
In October's circuit ideas, the ground line at

the bottom of the stereo phase and level
display circuit fell out of view of the printer's
camera. The three unterminated points at
the bottom of the drawing connect to
ground.
-015V
Negative band
-0.62V
Current
on
pulses
to motor
off
Min.
3ms
38
0V
330
on desired
Voltage atA
STEREO PHASE AND LEVEL
motor
Tr.
France
DISPLAY
47n
r\A/-
1k2
on to
off ratio
increases with error
Z80
GPM compatible
User transparent MULTI -TASKING

Up to 32K EPROM & 16K RAM
Watchdog crash protection
' Z80a
411r
PIO (one uncommitted)
120V x 2
3.10
23.01
28.46
35.45
64.28
82.92
99.76
139.89
298.89
'115 or 240V/CT sec
=`
2.59
13.43
19.03
250
350
500
1000
1500
2000
3000
6000
PrSec
100
200
RS232 & RS422 Comms
MAINS ISOLATORS
(60-1000VA Tap Secs)
VA
P&P
Price
'20
7.06
2.18
231
11.51
60
+1''
4/6 MHz Z80 CPU
Z80
CONTROL
CARDMASTER CPU
TRANSFORMERS
On board bus buffering
324
340
3.66
4.62
5.85
6.36
OA
OA
only.
Power-on jump hardware

400/440 to 200/240 CT
(601000VA Tap Secs)
P&P
VA
Price
Euro -card construction
NOW FROM 99 + VAT
60
200
250
350
500
CUB MICROCONTROLLER
Z80 CPU
4 x
Z80a PTO's (64 I/O lines)
4K Battery backed RAM (2K sup.)
2000
3000
6000
"
4K EPROM (2K MCV2.0 sup.)
Powerful monitor (MCV2.0)
"
Eurocard construction
NOW FROM 86 - VAT
STARBURST V1.31
CROSS ASSEMBLER FOR
CP/M80 covers four major
families of single chip uP's and
uC's
* 8048 inc. 8741/2 8748/9/50
* 8051 inc. 8031/28751 8744
* 6801 inc. 6800/1/2/368701
* 6805 inc. 68705 63705
Supplied with a complete set of
demonstration files.
STARBURST V1.31 95.00
+ VAT
Requires Z80 CPU
A
2.59
3.10
3.24
3.40
3.66
462
64.28
82.92
99.76
139.89
298.89
1000
1500
Z80a CTC
2.31
11.51
13.43
19.03
23.01
28.46
35.45
100
5.95
6.36
OA
OA
24/12V or 12-0-12V
2x 12V Secs. Pri. 240V
12V 24V Price P&P
2.92 1.10
0.3 A 0.15
0.5
0.25
3.08 ?.??
0.5
3.70 1.60
2
5.15 1.70
4
2
5.94 190
6 A
3
9.31 2.05
4
10.89 2.10
8 M
12 P
6
13.20 2.25
15.73 2.60
16 S
8
20
10
21.17 3.04
30
15
26.31 3.10
40
20
37.56 ??.?
60
30
53.92 4.90
41
62.09 5.65
83
1
CMR16 NOW FROM

165.00
Bare PCB's Available
1+
10+
28.50
25.65
C/M CPU
28.50
25.65
C/M I/O
CUB
23.50
21.15
CMR16
40.00
36.00
Manuals on request
60/30V or 30-0-30V
Pri 2x120V. 2x 30V Tap
Secs. Volts available
6,8,10,12,16,18,20,
24,30,36,40,48,60,
24-0-24 or 30-0-30V
60/30V or 30-0-30V
60v 30V Price P&P
1
5.69 1.85
0.5
1
2
8.67 1.91
4
2
11.15 2.20
16.12 2.34
3 A
6
4 M
18.38 2.55
8
10
23.23 278
5 P
12
26.50 3.02
6 S
16
8
37.25 165
43.37 3.99
10
20
49.98 465
12
24
SPLIT BOBBIN TYPES

6VA to 100VA
Two secondaries on each

e.g. 0-6V x 2 to give 6V or
12V or 6-0-6V
4.5V x 2; 61,1 x2
7.5V x 2; 9V x2
17.5V x 2; 20V x2
(20-0-20V)
Price
P&P
1.40
2.03
6VA
2.79
1.50
9
1.60
12
3.06
3.56
1.90
25
5.89
2.00
50
220
100VA
9.17
'hot 4.5V
2
3
4
5
A
M
P
S
6
8
2
4
6
8
10
12
16
10.31
1.99
16.96
20.54
26.22
37.22
46.61
50.85
254
2.75
2.89
3.70
3.99
4.20
EX -STOCK
30/15V or 15.0-15V
2.15V Tap Secs. Volts

available 3,4,5,6,8,9,
10,12,15,18,20,24,
25,27,30 or 15-0-15V
30/15 or 15-0-15V
30V 15V Price P&P
0.5
3.86 141
2
5.24 1.70
4
2
8.47 1.92
9.82 2.10
3
6
1
4 A
5 M
6 P
8 S
10
12
15
20
8
10
12
11.72
14.49
16.40
2.20
2.31
16
21.95
25.32
28.07
31.66
43.22
2.60
2.84
2.95
20
24
20
40
255
3.51
595
AUTOS
105,115,220,230,240V
For step-up or down
Price P&P
5.86 1.70
80
150
8.49 1.85
10.34
1.98
250
500
16.12 2.68
1000
28.79 3.25
1500
34.17 3.68
2000
51.09 4.62
3000
86.88 5.72
112.78
4000
0/A
5000
131.33
OA
7500
202.71
OA
10KVA
239.53
OA
CASED AUTOS
240V Cable input
115V USA socket outlets
VA
Price
P&P
1.76
8.34
20
11.33
1.87
80
150
14.67
2.20
250
17.87
302
500
29.32
3.19
4.34
1000
40.29
528
2000
73.33
105.26
OA
3000
INVERTERS
12/24V DC to 240V AC
100W
69.25
250W
218.40
500W
316.05
1000W
445.20
2000W
4000W
667.80
1275.75
CONSTANT VOLTAGE
TRANSFORMERS 1%
Spike -free stable mains
250VA
198.000/A
219.93
500VA
1KVA
2KVA
3KVA
4KVA
5KVA
6KVA ..
380.50
590.95
..1216.00
(1470.00
(1743.35
AVOs & MEGGERS

160.10
8MK6 (latest)
TT169 In -Circuit Transitor
Testor
C68.40
Megger Battery
80.30
Megger Crank
C132.50
Full range AVO5. Meggers
Fluke. Edgecumbe
WW MODEM PROJECT
Transformers T1, T2
7.59 pair Inc VAT,P&P
METAL OXIDE 1/4W
5% RESISTORS 60p/100
29 33. 47. 75, 390,

430. 5100. 560, 1K, 141,
143, 146, 1K6, 24, 3K,
349, 15K. 16K, 24K, 274,
39K, 56K, 82K, 100K,
110K. 120K. 1304, 1504,
2001 220K, 270K. 300K,
12,
10 values mixed
1/100
BRIDGE RECTIFIERS
IA
400V
.32
2A
200V
.52
35A
12.5A
100V
500V
3.00
3.62
VARIABLE AUTOS
1
ALSO VALVE MAINS

OUTPUT & MATCHING
TYPES
Stock items by return
96/48V. Pri 2 x 120V

Secs 2.36/48V
60.72,84.96.36-0-36V
or 48-0-48V
72/96 36/48V Price P&P
1
GNC ELECTRONICS
Little Lodge, Hopton Road,
Thelnetham, DISS IP22 1JN.
Tel: 0379 898313
5025V or 25-0-25V
2 x 25V Tap Secs Volts
available 5,7,8,10,13,
15,17,20,2530,33,40.
20-0-20 or 25-0-25V
50V 25V Price P&P
0.5
5.01 1.76
1
2
6.09 1.90
4
10.84 2.20
2 A
12.54 2.25
3 M
6
4 P
8
17.16 2.58
12
6 S
21.84 2.79
16
30.89 3.15
8
10
20
36.66 3.60
12
43.87 3.80
24
to 75A Enclosed
SPECIAL
0.210,240V. PRIMARY
Calibrated 0-250V
14,8.0,8.14V SEC
20VA 3 45 98PP.
PLEASE ADD 15% VAT TO

ALL ITEMS AFTER P&P
BARRIE ELECTRONICS LTD

Unit 211, Stratford Workshops,
Burford Road, London E15 2SP
Tel: 01-555 0228 (3 lines)
WINDING SERVICES
3VA TO 15KVA OR 3
phase Plus Toroidals
1
EDUCATIONAL METERS
Finger screw terminals
1-10A or 0-30V DC
78 x 89mm 3.98 each
50p P&P
POWER SUPPLIES
The TS3021 and TS3022 are Single and Dual
Laboratory Quality Linear power supplies
incorporating the following features:
D 0 to 2 Amps at 0 to 30 Volts (Dual on TS3021)
15 Dual 0.5" LCD display (Quad on TS3022)
Constant current mode

E Switched DC output
ED Coarse and fine controls
E Output protection against forward and reverse
voltages
LI Load and line regulation better than 0.01%
LCD display ensuring minimal RFI and
interference
El
TS3021 150
+ VAT
TS3022 280 + VAT
For further information contact:

Thandar Electronics Ltd., London Road, St. Ives,
Huntingdon, Cambridgeshire PE17 4HJ.
Telephone: 0480-64646. Telex: 32250.
I1,
ELECTRONICS LIMITED
CIRCLE
12
FOR FURTHER DE'I'N LS

39
PINEAPPLE SOFTWARE
Programs for the BBC models `B' with disc drive with FREE updating service on all software
DIAGRAM
PCB
Still the only drawing program available for the BBC micro which gives you the ability to draw really large
diagrams and scroll them smoothly around the screen stopping to edit them at any time if required.
Pineapple's unique method of storing the diagram information on disc means that the size of diagrams is
limited only by the free space on disc, and not the amount of computer memory you have available. (A blank
80 track disc will allow up to 39 mode 0 screens of diagram).
The superb print routines supplied with the program enable large areas of the diagram to be printed in a
single print run in a number of different sizes and rotated through 90 deg. if required. Full use can also be
made of printers which have a wider than normal carriage available.
The program is fully compatible with the Marconi Tracker ball described below.
PLEASE STATE 40 or 80 TRACK DISC &WHETHER STANDARD BBC or MASTER VERSION IS REQUIRED
This new release from Pineapple is a printed circuit board draughting aid which is aimed at producing
complex double sided PCB's very rapidly using a standard BBC micro and any FX compatible dot-matrix
printer.
The program is supplied on EPROM and will run with any 32k BBC micro (including Master series). Also
supplied is a disc containing a sample PCB layout to demonstrate the programs features.
By using an EPROM for the program code the maximum amount of RAM is available for storing component
location and ASCII identification files etc. (Up to 500 components and 500 ASCII component descriptions
may be stored fora given layout). These is no limit to the number of tracks for a given PCB, although the
maximum size of board is restricted to 8"
5.6".
Using a mode screen, tracks on the top side of the board are shown in red, while those on the underside
are blue. Each side of the board may be shown individually or superimposed. A component placement screen
allows component outlines to be drawn for silk screen purposes and component numbers entered on this
screen may be displayed during track routing to aid identification of roundels.
The print routines allow separate printouts of each side of the PCB in a very accurate expanded definition
1:1 scale, enabling direct contact printing to be used on resist covered copper clad board.
This program has too many superb features to describe adequately here, so please write or 'phone for more
information and sample prinouts.
PRICE 25.00
VAT
DIAGRAM UTILITIES
A suite of six utility programs which add additional features to the 'Diagram' drawing program. The utilities
include the saving and loading of areas of diagram to and from disc. The ability to display the whole of your
large diagram on the screen at one time (in either 4*4 or 8*8 screen format). The addition of borders and
screen indents to diagrams, and the ability to shift a whole diagram in any direction.
PRICE 10.00
VAT
PRICE 85.00
MARCONI TRACKER BALL
CONVERTER LEADS
This high quality device comes with it's own Icon Artmaster drawing program and utilities to enable
it to be
Converter leads to enable the Trackerbal to run mouse software and the mouse to run trackerball software
(inc. DIAGRAM). Please state which way round when ordering.
I
used in place of keyboard keys. Joysticks, or with your own programs.
PRICE 60.00 + VAT p&p 1.75

PRICE INCLUDING 'DIAGRAM' SOFTWARE 79.00
PRICE 8.00
VAT p&p 1.75
PRICE 25.00
VAT
d
Ba65
39 Brownlea Gardens, Seven Kings, Ilford, Essex 1G3 9NL.

Digital Decwriter Type LA30P
80
Cintel Mutual & Self Inductant Bridge Type 1854
40
Marconi Programmable FM/AM Modulation Meter
Type 1-F2301
140
Marconi Suppressed Zero Voltmeter Type TF1377 20
Telequipment Oscilloscope Type D31
45
Racal Four Channel Instrumentation Recorder Type
T3000 MkI1
100
Philips Transistor Leakage Current Meter Type
PM6509
55
Telequipment Oscilloscope Calibrator Type Cl
30
Wayne Kerr DC Differential Vokmeter Type M400 85
Ferrograph Series Seven Stereo Tape Recorder.... 95
Rohde & Schwarz
Frequency Indicator Type
Rohde 1
50
Rohde & Schwarz Selektomat Type BN 15221 /2 .... 50
Rohde & Schwarz Times Ten Frequency Multiplier
Type BN444421
50
Marconi Programmable FINIS AC/DC Voltmeter Type
M
TF2607A
ar
30
Heathkit R -C Bridge Model C -3U
15
Rohde & Schwarz Progr Synthesizer 0.01 Khz
120
Khz.SSN
200
Philips Volt/Ohm Meter Type GM6001
2
Hewlett Packard Oscilloscope Type 183A
250
Hewlett Packard Logic Analyzer Type 5000A
120
Tektronix Storage Oscilloscope Type 5648
150
45
Krohn Hite Oscillator Model 4141 R
Avo Universal Bridge Type B150
85
Rohde & Schwarz Polyskop 1 Type BN4344
100
Advance Power Unit Type BRM 40-05, 0-40v amp 60
Advanced Power Unit Type BRM 40-30, 0-40v
30amp
120
Transistor & Diode Tester Type TT537
35
Tete q ui p ment Oscilloscope
ope
043..
85
Texas Silent 700 printer
40
Tektronix Display & Keyboard Und Type 4010-1 .. 100
'DIGITALKERS'
Parrei Input, Mains 240v. Complete with data 10
Ex. Equipment Instrument Fans 41/2' 110 vac 2 each

240 vac 4. each.
Diodes 1N5406 10p each, 100 off 5, 1000 off 30.
Screws Pack of nuts, washers, tags self taps etc Sold

by weight
2.00 per Kilo
VAT
Tel: 01-599 1476
FOR FURTHER DETAILS
Pye Base Station Type F30AM High Band & Low

Band
220
Pye Base Station Type F3OFM High Band & Low
Band
250
Ban Base Station Type F401 AM High Band &
Pye Reporter Type MF5AM High Band & Low
Band
90
Pye Olympic Type M201 AM High Band & Low
IN VIEW OF THE EXTREMELY
PLACE
IN
THE
RAPID CHANGE TAKING
ELECTRONICS
INDUSTRY,
High Band & Low

Band
45
Pye Westminster Type W15AM High Band & Low
Band
50
Pye Westminster Type W15AM Mid Band
25
Pye Westminster Type W15AM Air Band Crystaled 3
channels, complete
75
Pye Base Station Type F9U UHF
90
Pye Base Station Type F9AM High Band
90
Pye Base Station Type F25FM High Band
90
Pye Base Station Type F412 UHF
200
Pye Base Station Typey F414 UHF
200
Pye Base Station Type F461 UHF
90
ITT Base Station Type 30LRU43A UHF
150
Pye PockeNone Type PF2FM High Band & Low Band,
Less Mike, Battery & Aerial
25
Pye PockeNone Type PF2AM High Band & Low
Less Mike, Battery & Aerial
25
Pye PockeNone Type PF2UB UHF Less Mike. Battery
& Aerial
25
Pye PockeNone Type PF5 UHF Less Battery
25
Pye PockeNone Type PFB UHF Less Battery
45
Pye Pocketone Type PF9 UHF Less Battery
45
Paer Ty PG1 AM High Band
35
Pye Mains Powerr Unit Type AC200
120
Pye Controller Type PC1
85
Pye Westminster Type W30AM Low Band Complete
with control gear
45
Pye Westminster Type LW15 FM High Band Less
gear
conAvo
30
Westminsterl 24vc
12vTyconverters
12
Bae Pocketfone Receiver Type PF
UHF Less
Battery
6
Pye PockeNone Type PF1 Rx/Tx with manual less
Battery
20
Weather proof mobile P.A. speakers 9" with mounting
bracket. 8 ohm 15 watt
10
Airtech UHF Fitter Duplexer, 3 Cavity Type Model
M450 -3A/14
25
PLEASE NOTE it is illegal to operate a transmitter with
out a licence.
1
Secondhand Pye equipment does not meet DTI

approval. All sets are sold less crystals, mikes.
speakers, power leads etc. unless otherwise stated.
CARRIAGE on RT equipment - Mobiles 2.00 each,
Base Stations 15.00 each. Please add VAT to the
total order inducing carriage.
WE ARE CASH PURCHASERS OF SUCH MATERIALS AND
WOULD APPRECIATE A TELEPHONE CALL OR A LIST IF

AVAILABLE. WE PAY TOP PRICES AND COLLECT.
R. Henson Ltd.
21 Lodge Lane, N. Finchley, London, N12 8JG.
5 mins. from Tally Ho Corner
Telephone: 01.445 2713/0749

CIRCLE
11
FOR FURTHER DETAILS
LOW COST UNIVERSAL PROGRAMMER

EPROMS EEPROMS MICROS
Completely self contained unit.
No personality modules required.
Controlled via RS232 serial interface.
Supports Intel, Motorola and Ascn
hex data formats.
Easily controlled by most computers
Fast and standard programming modes
Low and high byte programming for 16 bit data.
Byte, block and chip erase for Eeproms.
Eproms.
2508/16/32/64
2758
2716/32/32A/64/64A/128/
128A/256/512/513
27C16/32/64/128/256/512
68732.'64/66
Eeproms
2816A/64A
B. BAMBER ELECTRONICS
5
LARGE
QUANTITIES OF COMPONENTS BECOME REDUNDANT.
eyed Motofone Type MF5AM
TypePye
8 Bit
ALL ORDERS SENT BY

RETURN OF POST
The Pointer Rom is available separately for people already owning tracker balls, and comes with
instructions for use with the MASTER computer.
15
VAT
Use our Basic Compiler to produce direct 6502 machine code programs and ROMs for your own Basic
programs. Speed increases of up to 25 times are achieved.
POINTER
CIRCLE
BASIC COMPILER
TRACKER BALL for MASTER series

The Pointer ROM is supplied instead of the Icon Artmaster disc and enables the Tracker ball to work
directly with the MASTER series computers. (e.g. to use with TIMPAINT etc.). Prices are the same as for the
standard tracker ball.
PRICE 12.50
VAT
Station Road, Littleport, Cambs CB6 1 QE.

Telephone: Ely (0353) 860185
ASA
Callers welcome by appointment Mon -Sat until
8 pm.
Ate
Price uncased 295 plus VAT.
Stephens Road
CIRCLE
28
Cheltenham
48Z02
8748/48H/49/49H
Micro Concepts
2 St.
52B13/23/33
Micron.
Tel: 0242 510525

Glos
GL51 5AA
FOR FURTHER DETAILS
RESEARCH NOTES
C-mos failure
mode
confirmed
Recent work at BT Research
Laboratories at Martlesham
confirms a theory about how
c-mos integrated circuits break
down when they are subject to
electrostatic discharge. The
assumption has been that such
transients drive the protection
diodes into second breakdown
where heating melts silicon and
produces a conductive channel
which then shunts the gate in
question. This can happen either
as the result of a single highenergy transient or cumulatively
from a number of lesser static
discharges whose total energy
exceeds a certain value. In this
last case the junction behaves as
if each current pulse causes the
defect to grow a bit further, like a
sort of filament.
Confirmation that this is

indeed the mechanism has come
now from a mathematical model
that predicts the behaviour of
real circuits under different
transient testing regimes. Two
methods are used: one in which
fixed pulses are applied to a
c-mos gate until failure occurs,
the other using a sequence of
progressively higher voltages to
the same end. Chip failure is
arbitrarily defined as a leakage
current greater than 1 A.

The BT group predict from
their mathematical model that
there ought to be a clear
relationship between the results
of the two different methods of
i.c. testing. Not only that, but it
ought to be possible to precisely
predict the conditions under
which any particular i.c. type
would fail. Experiments in which
dozens of circuits were carefully
and systematically written off
have demonstrated that this is
the case. They have also shown
beyond reasonable doubt that
c-mos circuits break down in
exactly the way that had been
assumed.
Uncluttered
radar returns
As part of a programme to de-
velop its Blue Vixen doppler

radar Ferranti engineers have
found a new way to get rid of
unwanted reflections from the

ground. It was such reflections
from objects like cars that lead to
severe problems with the Nimrod early warning system.
Ferranti are employing a new
approach to software development, historically the most difficult part of complex radar development. Instead of taking an
aircraft aloft each time a test run
is needed, the Ferranti team have
brought the radar scene down to
earth using high -density recorders. Developed by Ampex, these
machines record data during a
test flight at 20 Mbyte/s which
can then by played back on the
ground to exercise the radar software as often as desired.
The software validation programme has paid attention to the
problems of land/sea interfaces
and the need to reject echoes
from fast moving vehicles. In
conjunction with the Royal Signals and Radar Establishment at
Malvern, Ferranti are accumulating a design archive which will
not only validate the software for
their own Blue Vixen doppler
radar project- as used on the Sea
Harrier - but also accelerate the
design of a new radar for the
European Fighter Aircraft (EFA).
World's
materials. Professor Lawrence

Rubin, who heads the work, is
now determined to make an even
bigger magnet, though not

simply to break records. Three
millimetres is a very small space
to do much in the way of experiments, so it's now necessary to
construct a unit with the same
magnetic field operating over a
larger volume. This next generation super -magnet may not exceed the record gauss rating, but
at $2 million it could well be the
world's most expensive magnet.
Solar cell costs

Every month sees the announcement of some development that
pushes the efficiency of solar
cells a little bit nearer the magic
25%. But for the end user the
cost per watt still remains obstinately high. A new development
from the University of Erlangen Nrnberg in Germany now
promises to combine improved
efficiency with low fabrication
costs to bring the price down by
half.
The cell consists of a layer of
silicon dioxide grown onto a p doped silicon substrate from
which aluminium contacts extract the powder. These are ap-
plied using an inexpensive
mechanical mask. The real key,

however, to the low cost is a
vapour -deposited silicon nitride
layer. This gets round the usual
lengthy high temperature diffusion process necessary to create
A research team at the Massachussetts Institute of Techno- the p -n juction. The nitride film,
logy has produced what is when chemically treated with a
claimed to be the world's most caesium solution, forms a sort of
powerful magnetic field. The sta- ìnduced' p -n junction, at the
tic in question is 336,000 gauss, same time as protecting the cell
that's getting on for 700,000 from corrosion and ensuring
times more powerful than the maximum absorption of light.
At present the electrical effiearth's magnetic field.
This phenomenal magnetic ciency of these polycrystalline
field is in fact the product of two cells is about 14%, a figure which
electomagnets in one. The first is the Erlangen group think can be
a more -or -less conventional unit improved to about 17%. They
with water-cooled windings. It also hope to see the cells in
consumes a mere nine mega- commercial production some
watts of power. The second mag- time next year.
net uses niobium wire, rendered
superconducting in liquid
helium. The two fields are combined and concentrated in a
3mm gap between two rods of
holmium.
The purpose of the device is
not to break records but to study Research at the UK's National
the properties of electrons in Radiological Protection Board
semiconductors as part of a re- has recently dispelled anxieties
search programme into new about possible health hazards
strongest
magnet?
Fluorescent
lamp u.v.
radiation
arising from long exposure to

fluorescent lamps. These lamps
generate their light from phosphors which act as wavelength
converters, absorbing the necessary energy from ultraviolet
radiation produced in a low
pressure mercury vapour discharge. It has been known for a
long time that u.v. radiation
especially of short wavelength
can lead to photokeratitis (arc
eye) and malignant melanoma
(skin cancer). Concern has
therefore centred on the fact that
fluorescent tubes inevitably emit
a small amount of u.v. radiation
in addition to the wanted visible
light. NRPB scientists tested a
whole range of different fluorescent tubes, selected at random
from different production batches. The same tubes were also
tested after 100 hours' use.
With all tubes there are inevitable peaks of u.v. output at the
mercury spectral lines of 313nm
and 365nm, though 'warmer'
coloured tubes generally have a
smaller output than `cool' ones.
For most tubes the u.v. output
appears to decrease with age
faster than the loss of visible
light, possibly due to a photochemical reaction which makes
the glass less transparent in the
u.v. region.
At no time, however, does the
u.v. output of any tube come
near the limits adopted in the UK
for occupational exposure. This
appears to be so even at the
lighting levels recommended for
machine shop areas (1000 lux). It
can therefore be assumed that no
danger exists from any visible light fluorescent tube under normal conditions of use.
Locating
lighting strikes
To evaluate protective measures
against lightning the Electricity

Council's Research Laboratories
at Capenhurst have devised a
system that plots the occurrence
of lightning strikes in real time.
It makes use of the fact that
lightning generates powerful
electromagnetic pulses in which
the bulk of the energy is concentrated at frequencies between 1
and 100kHz.
Three special d.f. stations listen out on a frequency of 2kHz
for the characteristic `signature'
of a lightning strike. Each sta-
41
Film vs h.d.tv
tion uses a combination of loop

antennas to compute the bearing
of the strike to within 0.05 degrees. This information is then
fed by telephone line to a computer at Capenhurst which generates a 'fix' by combining the
information from all three stations. Strike data arriving within
any 2.5 ms window are assumed
to relate to the same event.
The output appears on a v.d.u.
as a series of crosses superimposed on an outline map of the
UK from which it is possible to
watch a storm as it develops and
moves across the country. The
information will be available
directly to local electricity
boards and also archived for
future reference.
Laura Scott, who heads the
project, says that the information will make it safer for linesmen working up pylons and may
also allow power to be diverted
Although the Japanese 1125 -line

60 -Hz h.d.tv system failed to
achieve world-wide acceptance
at the CCIR meetings last May, it
has succeeded in wakening up
the film industry to the need to
consider new technology and
techniques that could provide in
cinemas greatly improved picture and sound quality. Last year
the Society of Motion Picture &
Television Engineers (SMPTE)
set up a powerful study group to
consider the possibility of changing the frame rate of cinema and
television films from the longestablished standard of 24 frames
per second to the 30 frames per
second already used for some TV
film commercials in the USA.
The use of 30 frames (60 images or "flashes" a second) permits much brighter and crisper
pictures without introducing
away from a line that is

threatened by a storm.
Lightning costs the electricity
supply industry 1 million per
year in damaged equipment and
lost revenue.
Fusion `when'
rather than 'if'
Another step in the race to
generate a useful amount of power by nuclear fusion was taken
recently by a research group
working at Princeton University
in the USA. In their tokamak
reactor they generated a temperature of 200 million degrees celsius for a third of a second. That
is ten times hotter than the
centre of the sun and the highest
temperature ever recorded in a
laboratory. Such temperatures
are necessary to make hydrogen
atoms fuse together to produce
helium and, in the process, release energy. (Solar fusion can
occur at lower temperatures due
to the huge gravitational force).
During the short time the Princeton reactor was able to sustain
the high temperature, an estimated 10 x 1012 hydrogen atoms
fused, releasing about 10kW of
energy. Had the experiment used
a deuterium/tritium mixture,
this might just have topped
1MW.
Although nuclear fusion did in

fact take place, the overall efficiency of the reactor is still far
below unity. The hydrogen plasma had to be heated ohmically,
by r.f. energy, and by the injection of energetic particles. This
last method alone consumed

17MW of power. Yet fusion scientists are now talking about
42
`when' rather than 'if. The European tokamak reactor at Culham

in Oxfordshire still holds the
record for the longest sustained
plasma confinement - a factor
just as important as ultimate
temperature.
So if safe, clean, inexhaustible
fusion power isn't just around
the corner, it is at least making
the sort of steady progress that
justifies the confidence of those
working in the field.
Auto speed trap

Over a hundred years ago the
first traffic lights gas powered
blew up. Fifty years later they
made a comeback, then electrically powered and controlled by
pressure pads set in the road.
Now work at the University of
Manchester Institute of Science
and Technology, the University
of Sheffield and the Transport
and Road Research Laboratory is
on the verge of creating a third
generation of traffic control sys-
any perceptible flicker. At present British cinemas rarely use

screen brightness levels more
than about 12 foot-Lamberts,
compared with the 16 ftL of
many American movie -houses.
One result is that British film
producers admit that their films
look better when shown in the
USA. The adoption of 30 frames
would permit screen brightness
to be raised to over 20 ftL.
The SMPTE have also been
studying the possibility of multichannel digital sound recorded
on compact discs (or digital audio tape?) electronically tied to
the film by the adoption of the
television VTR -editing technique
of time -coding each frame. With
this system the sound would not
tems.
lose sync. even if the frames had
Instead of pressure pads, a been cut from the film or reels
system has been devised which projected out of sequence.
enables information to be taken
For European tv, a 30 f.p.s.
from a video camera so that film standard would
end the
passing vehicles can be counted practice of running 24 f.p.s.
film
automatically and their speeds at 25 f.p.s. to facilitate
the use of
measured accurately. If a com- flying -spot telecines, but
at least
mercial manufacturer can be some television engineers would
found, the image anlaysis of Trip welcome 30 f.p.s. film
though
(traffic research and image pro- opposed to a 30 f.p.s.
(60 Hz) tv
cessing) should lead to greatly production standard.
improved traffic control. Team
leader Dr Michael Hartley of
UMIST anticipates that this
might well require a venture
capital sum of over 1/2 million.
The work so far has involved a According to a press release issued
system to analyse pictures from by the Department of Energy, two
tv cameras mounted on motor- major wind energy projects are unway bridges and high buildings. der way. One is a 3mW (sic) 60m
This research has thrown up diameter horizontal -axis machine
many problems associated with in Orkney whilst the other is a novel
variations in lighting and a high 25m vertical axis machine at Cardata rate. Trip has nevertheless marthen Bay. Negotiations are said
now reached a stage where it can to be well advanced for a '1 mW
recognise even small motorbikes stretched version' at Richborough
under the foulest weather condi- in Kent. Should be enough to power
tions.
about three pocket calculators.
World's smallest
windmill?
TFEEDBACK
FFT
David Gibson (Letters Sept.86) is
being unfair to the Fourier transform! The Fourier transform,
put simply, is a mathematical

tool which can transform or
'map' from one domain to its
inverse. Frequency and time are
inverse domains, and so the
Fourier transform can be used to
map from one to the other. There
are limitations to what the transform can handle, (many of which
are overcome by using the Laplace transform - but that's
another story), but low-pass filters whether real or 'perfect' are
not among them.
A non-repeitive frequency domain function, such as low pass
filter (l.p.f.) whose frequency response never quite reaches zero
at any frequency, has a finite length time -domain transform.
This is the realm of real filters. As
a filter approaches perfection,
and has more and more ultimate
attanuation, the time -domain
response last longer and longer
(the filter 'rings') and in the
limit, a perfect filter with infinite
attenuation in the stop -band
would have an infinitely long
time -response (it would 'ring' for
ever). The Fourier transform of
such a frequency response is
sint/t where t is the reciprocal of
the filter bandwidth.
A feature of all time -domain
transforms is that they are symmetrical about t=0, and so there
is apparently as much response
before t=0 as afterwards.
This leads to the realisation
that the 'well known phenomenon' mentioned by Mr Gibson that the Fourier transform
predicts that a perfect l.p.f. has a
time response which begins before the impulse at t=0 is going
to be true also for real l.p.s. So
what has gone wrong?
The answer is that this is a
misapplication to the transform.
The process of predicting a filter's time -domain response resulting from an excitatory impulse involves convolution. It
would need a complete article to
satisfactorily explain what convolution is; however the salient
features of convolution are as
interval t.
b) as the convolution proceeds,
the excitatory impulse is scanned from 0 to t in the time
domain, while the filter's
time -domain response* is

scanned backwards from t to 0
Fourier transforming the convolution gives us
F[f(t)*h(t)]=Ff(T).Fh(t-T)
=F(w).H(-w')
where T runs from 0 to t (1)
during the convolution
represents the Fourier transform, and * represents convolution.

F
If f(t) is the vanishingly short

unit impulse, and h(t) is the
wanted response to this impulse,
then the L.H.S. of equation (1) is
simply equal to h(t). On the
R.H.S. of the equations, Ff(t) is
unity, and so we can rewrite
equation (1):
h(t)=H(-w')
(2)
What equation (2) says is that the

impulse response is given by the
inverse Fourier transform of not
H(w) (the frequency response)
but H(-w'), the frequency response run backwards, with an
offset of t. Now t is simply the
time required for the impulse
response to delay to zero, so we
take the inevitably symmetrical
H(w), reverse it, and move it so
that t=0 correspondents with
the point where the response
reaches zero.
As the l.p.f. response becomes
steeper, t becomes longer, and
tends towards an infinitely large
value for a perfectly steep filter.
This accords with experience,
which is that the sharper the
wanted filter cutoff, the more
elements the filter requires, and
the larger the group delay becomes. The mystical perfect filter would need infinitely many
elements, t would be inifinite,
and so the filter would never
given any output (thereby never
having a chance to 'ring' indefinitely as suggested earlier in
the analysis)
Brian J Pollard
Watford
follows:
a) it runs for the time interval *i.e. the time response to a
required for the resulting im- vanishingly short unit impulse
pulse response to die away to the response we are interested in
zero. Let us call this time deriving.
Relativity
Professor Butterfield has presented a welcome and delightfully simple approach to explaining
the seeming oddities of relativity. I am, I confess, still not fully
convinced of the "correctness" of
the whole concept (Butterfields'
article aside).
The invited assumption that
"energy has inertial mass" is not
at all straightforward (like the
reasons to assume c is constant).
I would suggest the only reason
it seems to be more acceptable is
that from experience we know it
is worse to be hit by a fast moving
object than by a slower moving
object. To hedge a 'little' extra
mass on top of this is, I suppose,
more easily grasped. However, to
explain it (this small extra mass)
one needs the results based on
this assumption! (equation 5).
The evidence in favour of relativity is overwhelming, considering observed effects in nuclear physics (e.g. particle decay
times) and astronomy (gravity
lens), yet I feel sure most people
would agree that although relativity gives a possible (and
quite usable) explanation for
observed events, it does not give
a reason and is far from complete.
Indeed, if one were to assume
our hypothetical observers were
blind, and must use sound to
transmit and perform the necessary logical steps, we see that
these poor observers believe
their object has disappeared
upon reaching (or passing) the
sound barrier: all talk of aether
and such aside, no convincing
could persuade our blind friends
that the object was still there.
Despite my allegiance to relativity, I'm still anxious to know
whether anyone has tried, for
example, weighing a spinning
centrifuge rotor or a very large
charged capacitor to measure
any weight differences between
the high and low energy states.
Other relativistic ideas which
bother me are, I'm sure, often
suggested brain teasers, such as
"What happens to a top spinning
at a high angular velocity?" or
what happens to the magnetic
field of a superconducting ring as
it is lowered into a black hole?"
It seems gravity is inextricably
involved, and will remain a dark
horse until a grand unified
theory is put forward. I fear, that

by then, the mathematics will be
quite incomprehensible to this
humble reader. Meanwhile, time
has once again won by eluding
true definition, and quietly slipping by.
Michael J Snoswell
Adelaide, 5067
South Australia
Professor Butterfield is being
fishily eel -like with his shoals of
evidence, and apparently cannot
digest the worm which he nibbles at. In all my letters over the
past couple of years or so I have
never doubted Einstein, and my
attack has been an effort firstly to
enlighten those who do not
understand the matter, and

secondly to enable the specialists
of the world to understand it
better than they do, and that
without inaccurate presumption.

Before wielding my two-edged
fishing rod with its horse's head
handle, let me congratulate the
Prof. upon coming up with creation and catastrophe as a vital
part of the picture (poor Albert)
even if he only did it subliminally
with a Freudian slipping clutch
like the monetarist snake!
The Prof. states: "Since a packet of energy should not be instantaneously movable from A to B as
we see it, then it must have
inertial mass!"
NOT SO, Prof.: if the energy is
carried by a wriggling device
which has inertial mass, it will be
similarly delayed. Can't you see
that? Such a device is the LSM,
the basic postulate which Einstein seems to me to have had at
the back of his mind when he
stated that he could not conceive
an empty space with nothing in
it, a postulate which he found
difficult to communicate to the
specialists of the world because
he had not completed his concept. I say again, back tp the
drawing board, Prof.!
The concept at which I believe
Einstein would have arrived, had
he had enough time, is in the
hands of Mr Editor who might
publish it when and if he sees fit,
or may not because it is better for
improvement of mind to come
from within by personal solving
of the puzzle, rather than from
without: logic which is a part of
personal experience is more easily believed than that which is
provided by others.
43
FEEDBACK
I recommend that Prof. Butterfield differentiates again in
order to clarify his mind by
separating energy from mass, so
making it an individual entity: he
might then learn something to
his advantage (which simplifies
his envisaged mind -boggling
rules) and discover how Einstein
evolved aut of Newton without
denying him. A second further
differentiation will bring him to
time alone, and there is nothing
simpler than that.
Finally, I congratlate Prof.
Butterfield in recognising (if
again subliminally) that I am a
Leo, but crouching in his den
and lying in wait!
James A. MacHarg
Wooler
Northumberland
In his June article 'Relativity

Simplified' Professor Butterfield
attempts to derive Special Relativity by considering accelerated motion rather than uniform
motion (i.e. motion in which no
internal stresses are generated).
By so doing he completely
obscures Einstein's major
achievement. That achievement

was to realise (with some assistance from Minkowski) that the
contemporary view that in a
vacuum electromagnetic effects
propagate as waves in an ether
could be replaced by the view
that in a vacuum the propagation
of electromagnetic and gravitational effects is determined by
the geometrical structure of the
space-time continuum. This
view takes some swallowing, but
I do not believe that any consistent picture of Special Relativity
can be developed without it.
Generalisations which attribute
increasingly elaborate structures
to the space-time continuum
underlie not only Einstein's very
successful theory of gravitation,
but also the much more recent
developments in the theory of
the early history of the universe.
In all these theories the idea of
simultaneity (i.e. of a universal
time) has to be abandoned.
However Special Relativity retains reasonably close links with
classical physics because in its
simultaneity remains a valid
concept in any particular inertial
frame. The weakness of most
presentations of the theory is
that no attempt is made to find
an explicit expression for the
effect of simultaneity breakdown, and Professor Butter -
44
field's is no exception. I have

given the required expression
elsewhere(1). His statement, at
the beginning of the section
'Simultaneity and measuring
rods', that 'the length of an object must be defined in terms of
simultaneous measurements at
the two ends', is therefore incorrect. Instead this is merely a
convention, and a bad one at
that, since it leads to all the
familar difficulties with the
assertion that the length of a rod
changes as a result of its motion,
even though it is free from internal stresses.
In the section "Light and the
'Impact Theory- the moving
clock can be regarded as passing
two distinct clocks at rest in the
L1 frame at the positions x1 and
x2. These encounters remain distinguishable events in the frame
1,2 of the moving clock however
fast it moves, even though in that
frame the measured time interval between them may be very
small. Thus all his conclusions
about 'impact theory' are simply
special pleading. It is true that
the 'interval' in space-time between any two events on the
world line of a photon is zero, but
in this complex four-
dimensional space the statement

turns out to embody Einstein's
hypothesis about the invariance
of the velocity of light.
I have little doubt that the key
to understanding Special Relativity is to concentrate on un accelerated motion and on
events. Accounts in terms of
such concepts as time diltation
(time intervals), and especially of
the so-called Lorentz-Fitgerald
contraction (space intervals)
tend to run into difficulties,
which can usually be resolved as
soon as one takes the trouble to
specify the events involved.
C.F. Coleman
Grove
Oxfordshire
Reference
Coleman, Eur Jour. Phys.
40983)240-247
C.F.
In view of the interest in relativity shown by many Wireless

World contributions, it is opportune to draw attention to the
experimental discovery reported
by E.W. Silvertooth in the 14th
August issue of Nature. His findings are important because they
clearly invalidate Einstein's

Principle of Relativity. I have had
the opportunity of discussing

this experiment at some length
with Mr Silvertooth and offer the
following comments on its significance.
Essentially, it has been found
that the spacing between nodes
in a standing wave set up by two
oppositely -directed light rays

from the same laser source varies
with orientation of the apparatus. The effects observed, which
were monitored over several
months, indicate a detection of
the Earth's motion relative to the
preferred frame in the direction
of constellation Leo, at a speed
indicated by a typical measurement to be 378 km/s. This should
be impossible according to Einstein's theory.
The feasibility of the experiment, which was sponsored by
the US Air Force, depended upon
the prior development and fabrication of a special type of standing wave sensor, described in
Applied Optics in 19832. This
could scan through the laser
beam and detect the position of
the standing wave nodes with
high precision.
Crucial to the justification for
the experiment was the realization that the null finding of the
19th century Michelson-Morley
experiment is not a conclusive
test of light speed anisotropy. It
merely tells us that the roundtrip transit of a light signal over a
given distance is invariant with
motion or change of orientation
of the apparatus. Though consistent with isotropy, this can
equally be consistent with anisotropy, meaning that the light
speed in opposite directions
along any given orientation of
the light path and referenced in
the preferred (ether) frame can
be the same, but that it might
vary with the orientation. There
could be physical interactions
between the two waves that set
up the standing wave system,
modifying the common light
speed in the preferred frame.
An example of such a condition is provided by a resonant
spherical cavity of fixed radius R
moving through the preferred
optical frame. It can,sustain radial oscillations of fixed roundtrip duration 2R/c in a direction
of a motion -component velocity
v given by:
R/(c'
-v)+R/(c' +t)=2R/c
provided the light speed in-
creases from c to c' equal to
c(1+v2/c2). The conventional interpretation of the MichelsonMorley experiment is that c'

must equal c, but this need not
be the case if we accept light
speed anisotropy.
In reality one can suppose that

the properties of the ether are
regulated by resonance effects
which account for the null of the
Michelson-Morley experiment.
However, the properties just described must then show up in an
experiment which measures the
spacing between the standing
wave nodes and this is exactly
what the Silvertooth experiment
accomplishes. In effect, over the
test length L, he measures the
difference:
L/(c'-v)-L/(c'+v)
=2(L/c')(v/c)
and so determines the v with
first -order precision.

The fact that the test gives a
positive result and not a null
confirms the existence of an
ether and disproves Einstein's
theory. It sustains an argument
by Ives3 that the Sagnac effect, by
which rotation is sensed optically as if there were an ether, need
not depnd upon a rotation of the
apparatus to justify its operating
principle. Indeed, Silvertooth
claims that his experiment is a
linear adaption of the principles
of the Sagnac experiment.
References
Silvertooth, Nature, 322, 590
(1986).
2. E.W. Silvertooth and S.F. Jacobs,
Applied Optics, 22, 1274 (1983).
3. H.E. Ives, Jour. Opt. Soc. Am., 28,
296 (1938).
1. E.W.
H. Aspden,
Department of Electrical
Engineering,
University of Southampton
The vector equation below gives
the magnetic field H associated
with an electric field E moving

with velocity V in free space of
permittivity e:
H=eVxV
If E is
due to an electric charge of

mass m, its magnetic energy in
free space of volume T and permeability u, can be equated to
the kinetic energy to obtain

1/2u
f H2dT = 1/2ueV2f eE2dT=1/2mV2

which gives E=1/2mc2
where E=1/2e f E2d' is the elec-
FEEDBACK
trostatic energy of the charge
and c=(ue)-1/2 is the speed of
light in free space.
I would be grateful to have
readers' comments on the discrepancy, by a factor of 1/2, between the derivation made here
and Einstein's law E=mc2
M.D. Abdullahi,
NCATC,
Zaria,
Nigeria.
Mathematical
Rake's Progress
In the September letters, D. Gibson states that, if Fourier transforms are used to calculate the
response of an ideal low-pass
filter to a pulse input, the calculated output begins before the
input pulse itself. Since he fails
to mention the phase response of
,the filter, it seems that he has
arbitrarily assumed that the filter has no affect on the phases of
the components of the spectrum
of the input signal.
However, in the frequency domain one cannot make an arbitrary choice of the amplitude response as a function of frequency, and then go on to do the same
thing for the phase response,
without running the risk of describing a physically unrealisable
waveform filter, and that is what
he has succeeded in doing. An
amplifier with a pass band
stretching from d.c. to a sharp
high-frequency cut-off can be
regarded as a kind of low-pass
filter. It is notorious that the
sharper the cut-off is made the
more rapid is the phase variation
near cut-off, and the more ringing one sees on the leading and
trailing edges of square -wave
pulses passed through it. If Mr
Gibson carries out a calculation
using realistic values of the
phase shifts produced by his lowpass filter he will find that the
response to any feature of the
input waveform comes after that
feature, as it should.
The conditions under which a
filter transfer function may represent a physically realisable filter have been expressed in terms
of Hilbert transforms (see
Bracegirdle's book on Fourier
transforms). It is worth remarking that Fourier transforms can
be applied to functions of spatial
coordinates as well as to func-
tions of time, in which case the

preferred direction given by
`time's arrow' does not exist, and
the entities analogous to filter
transfer functions are subject to
no such limitations. Entities of
this kind are widely used in
image processing.
C.F. Coleman
Grove
Oxfordshire
Reference
R. Bracegirdle, The Fourier Transform and its Applications, McGrawHill Electrical and Electronic Engineering Series, McGraw-Hill, New
York, 1965.
S5/8
In reply to Mr Hayward's letter in
the September issue, I agree that
international standardization is
desirable and has always been a
goal I have sought to achieve,
and will continue to seek after
S5/8 becomes a British Standard.
Criticizing the quality of DIN
connectors is as pointless as
praising the quality of D -type
connectors. Any connector for
which there is a volume demand
will attract the attention of the
`cheap and nasty' manufacturers
and I have seen atrocious examples of both D -type and "Centronics" type multiway connectors
as well as very poor quality BNC
and UHF coaxial types. Judging
DIN connectors by the worst
available is a gross injustice.
There are high quality metal shell versions available, such as
those maufactured by Futters (as
sold by RS and Verospeed), that
are quite satisfactory for both
home and office use. Beyond
that, I am confident that Belling Lee would be pleased to inform
you of the industrial and military
success of the Bleecon DIN
range. The already popular DIN
connector is all set to become
even more widely used for data
interconnections, with the in-
evitable trend toward serial

transfer.
Beyond quality of construction, how much performance is
one to expect from a connector
fitted to an item of IT equipment
with a three or five year life? Just
how many insertions and withdrawals is it likely to experience?
The question of bipolar signalling is a non -question. It is
nothing more than a historical
hangover from polarized teleprinter magnets and has no place

in modern, low-power, single
supply equipment. The choice of
Epson portable equipment, as an
example, for the use of RS -232 in
a battery -operated environment
is interesting, as it proves my
argument. Yes, Epson have put
an RS -232 interface into all three
of their portable computers.
However, in the PX-8, the RS232 interface adds over 55 components and such a significant
battery drain that a software controlled switch circuit is used
to disable it when not in use, to
save power. Epson first used this
approach in their HX-20, where
turning on the RS -232 interface
roughly doubles the battery consumption. The lower the power
consumption of the processor,
memory and display, the worse
the problem becomes.
The use of RS -232 voltage
levels by Epson to communicate
with their PF -10 battery disc
drive is particularly pointless. It
is a non-standard interface, communicating in a non-standard
protocol at a speed outside the
RS -232 specification, and solely
dedicated to Epson equipment,
yet they felt it necessary to go to
considerable expense to use
bipolar signalling in units that
will never be called upon to
interface with RS-232 equipment and where there is no
technical justification whatever
for using d.c.-to-d.c. converters
to generate bipolar voltages to
send data down one metre of
cable.
There is no question that dif-
ferential, balanced signalling,

such as RS -422, or the newer
RS -485 party -line system, offers
better data transmission, but at a
financial and power cost which

has rendered it less popular. RS 449 was not exactly a runaway
success and, more recently, the
SCSI standards offers the choice
between single -ended (open collector) or differential interfaces - guess which most manufacturers are implementing!
The MC3486 receiver and
MC3487 transmitter are out of
the question for battery -operated
equipment, together having a
worst case power consumption
of 190 milliamps, a value embarrassing even in mains equipment, with devices such as the
highly capable 64180 containing
processor, memory manager,
dual uarts, bit -rate generators,

dual timers, interrupt controller, dual d.m.a. controller and
clock generator, all consuming
only 20 mA maximum at 4MHz.
The days of "200mA doesn't mat-
ter" thinking in equipment design are over. Also, I do not

consider the MC3486/7 pairing
as low-cost. It costs at least three
times as much as 1488/9 combination and over five times as
much as an HC14 gate, not taking into account the cost of
providing that 200mA and venti-
lating the heat dissipation

thereof!
Finally, to achieve a "plug and -run" interface (the goal of
S5/8 and, I suspect, the goal of us
all), a standardized data structure is essential. Eight -bit working is now the norm and there is
no point in accommodating
shorter word sizes by changing
the framing. Lateral parity is also
questionable. It is seldom possible to organize retransmission
on a per -character basis and
block error detection is much
more efficiently performed using
CRC, or similar, techniques and
does not impose a 10% burden
on the character frame.
On the question of the data
signalling rate, the increasing
use of microprocessors in devices removes the need to match
the data interchange speed to the
physical restrictions of the
attached device. 9600 bauds is
already a de -facto standard with
IBM, DEC and Intel and is being
incorporated into new standards
including the ISO Standard
`smart cards'.
A.S. Hardie
Technical Director
Oval Automation Ltd
Littlehampton
Sussex.
Having reviewed the early proposals for S5/8, and contributed,
along with many others (all unheralded), to the development of
a useful idea into a proposed
standard, I read Mr Hardie's articles with interest and waited for
the criticism. So far, you have
published only one letter (from
L. Hayward, September, p.13)
and, as expected, his, criticisms
miss the point in all except one
area: the lack of international
agreement.
Mr Hayward objects to using
DIN circular (audio) connectors
on the grounds that they are not
45
FEEDBACK
robust enough for office use.
Some cheap DIN connectors are
indeed of very poor quality, but
others are very acceptable. Why
else would IBM use them as
keyboard connectors on the PC
range, or Hewlett-Packard on
bar code reader wands? We
purchase cast -body 5 -pin DIN
connectors for 50p each - compare that with a 25 -pin D plug
plus a good quality cover (i.e. one
that stays in place and clamps the
cable properly and provides r.f.i.
screening) for around 1.50.
And DIN connectors are at least
rewireable, unlike telephone type connectors.

Unipolar signalling with a
ground reference has been used
successfully for many years in
small computer systems snd
computer terminals. The t.t.l.
level Centronics printer interface is one example, microcomputer disc interfacing is
another, and many computer
keyboard interfaces are t.t.l. In
some cases, the equipment at
both ends of the signal cable is
mains -powered, yet well designed interfaces performly reliably. S5/8 follows this long line
of development.
S5/8 is a very low -power system. The recommended S5/8 circuitry consumes only micro watts of power. RS232 consumes
about 50mW, RS422 more like a
1/4 watt. S5/8 is intended for use
in lightweight battery -powered
equipment. Yes, I would prefer to
see a bipolar system, if only
because S5/8 cannot interword
with RS423 (as used, for example, in the BBC micro), but S5/8
is a case of 'horses for courses'.
S5/8 is intended to be a 'plug
in and go' system. Hence the
fixed signalling rate and word
structure. No configuring, no
debugging, no technicians, no
test gear - just buy it and use it.
The increasing use of 'intelligence' (i.e. an on -board microprocessor) in items of equipment
which would use S5/8 means
that Mr Haywards 'differing requirements' will be catered for by
software in each product.
New RS232 interface circuits
are making designers' lives
easier - e.g. the MAX232 from
Maxim, incorporating two transmitters, two receivers, and
10V charge pump generators in
one 16 pin i.c. - but there is still
no easy way of designing a very
low power bipolar interface. C -
46
mos circuitry implementing a

high impedance version of
RS423 (with receiver input
threshold voltage control so as to
allow interfacing with S5/8 or
t.t.l. transmitters) would be a
great step forward, as long as a
transmitter and receiver could
be packaged in one i.c. running
off a single 5 volt supply. Semiconductor manufacturers please
take note.
Peter W Tomlinson
Managing Director, IOSIS
British Telecom
and the amateur
morse test
In September 1986 issue of your
magazine the reference in 'Com-
munications Commentary' to
BT's activities in connection
with the amateur morse tests
contained inaccuracies which I
should like to correct.
It was the Department of
Trade and Industry (DTI) which
decided to put to competitive
tender the contract for conducting the amateur morse tests. BT
have never given notice, formally
or otherwise, of a desire to relinquish its involvement in the
tests. Therefore your statements
that BT first decided to give up
the tests and then changed its
mind are quite untrue.
Also, I should like to explain
why BT issued a notice to its
employees to seek advice from
the appropriate Department before committing themselves to
assisting RSGB in running
morse tests. (BT did not 'order'
its employees to take no part in
running the RSGB tests as stated
in your article). The reason for
this was that due to the loss of
contract an additional redundancy was created in a small specialized workforce which is already
having to be reduced due to
other factors outside our control. BT hopes to have the opportunity of re -tendering for the
work in future and would not be
acting in the interests of its staff
if it supported the provision of
unpaid examiners to replace a
job.
No directive was ever issued to
our employees to give up their
existing RSGB activities such as
teaching morse or providing
equipment at test centres; I hope
they will avail themselves of the

enquiry facility included in the
notice before assuming that they
cannot participate in any RSGB
activity connected with the

amateur morse test.
F.R. Barnfather
British Telecom
`Q'and
bandwidth
In his stimulating article on 'Q'
(E&WW July 1986 pp51-3) Dr
Smith omits to mention a frequently overlooked fact concerning a series -resonant circuit in
which frequency (w or f) is the

variable - the 'approximate' relationship between Q0, the resonant frequency wo and Ow the
frequency range between the
-3dB points is exact. An outline
proof is given here.
Z=R[1+jQaf(w)]
(1)
where f(w)= [(w/wo)- (w/w)] (2)
The -3dB points occur at wH
and wL for which
(3)
Qof(WH)=-Qof(wL)=1
From (2) and (3), after some
al ebraic reduction,
Wo=WHWL
(4)
and Ow=(WH-wL)=(WO/Q0) (5)

Note that the derivation of (5)
does not require Qo to be 'large'
or Xw<<<wo
B.L. Hart
Leigh -on -Sea, Essex
Emir
-wog
Uncivil
Servants
In a letter (July, 1986) John C.
Rudge remarks "If any civil servants in the British Standards
Institute...". No government departments are called Institutes.
Certainly the Federal Bureau of
Standards is a government department in the States but the
Q
the author of an article with
the above title in your issue of
July 1949, perhaps I may be
allowed to comment on 'Q' by Dr
K.L. Smith in a more recent
issue (July 1986). As Dr Smith
starts his discourse by referring
to a student using a (presumably
direct -reading) Q -meter, I was
surprised he didn't go on to point
out that an instrument of this
kind (unless unknown to me it
has been radically redesigned)
does not read Q unless the tuning inductor has negligible self capacitance. For Q = Q' (C +
Co)/C, where Q' is the meter
As
reading,
Co
is the self -
capacitance and C the added

capacitance. And that is not the
only cause of error in these
meters.
And although the Q of a reasonant circuit can be correctly
measured from a resonance
curve (Dr Smith's Fig. 3), it is
perhaps desirable to mention
that resonance curves come in
many kinds, as I explained in
January 1953. Admittedly, the
differences are negligible unless
the Q is less than about 5.
Q is often equated with the
magnification factor m, but
again it is only for small values
that the differences can be
appreciable.
Cathode Ray
The author replies
Cathode Ray is quite correct in
pointing out the effect on Q
when an inductor with a self
capacitance co is measured. I did
not concentrate on methods of
measuring Q in my review article
on the topic, but any interested
reader could very well look up
Cathode Ray's original article, or
his books on laboratory tech-
nique.
One other interesting applicaBritish Standards Institution is tion that I omitted from my
independent.
article, is the Q of space itself.
I'm reminded of a note in that Lossless empty space has
an infiamusing publication "The Col- nite Q, so an EM vibration proplapse of Flats at Ronan Point, agates for ever without
losing
Canning Town" which blamed any energy - it is just dispersed
the Institution for a Standard it according to the inverse
square
had not even contemplated pro- law. On the other hand,
a lossy
ducing, on the robustness of region, such as the ionosphere,
tower blocks, without appreciat- has a Q given by the ratio of the
ing that the Institution had abso- magnitude of the displacement
lutely no responsibility to any- current density to the conducbody in these matters.
tion current density
Bernardlones
WE
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Active op -amp compensation

This general method for simulating non -inverting
voltage -controlled voltage -source building blocks
reveals several new structures, all with negligible phase
and magnitude error.
AHMED M. SOLIMAN
of the op -amp. Without any loss of generality
let Vol represent the output of the compensated non -inverting amplifier as shown in
Fig. 1. From equation 1 the generalized
expression for the transfer function of the
circuit, equation 3, can be written in the
form T(s) = (C/B) .E(s), where E(s) is an
The non -inverting voltage-controlled

voltage source is a basic building block
in active filters and oscillators. Unfortunately with the exception of some very low
frequency applications, the assumption of

ideal behaviour cannot always be sustained
and in particular the complex nature of the
voltage gain must be accounted for. It is
well-known that the finite gain-bandwith product of the operational amplifier degrades
both the phase and the magnitude of the
conventional v.c.v.s. building block'. Most
recently, active -compensated v.c.v.s. networks using two and three op -amps have
2-5.
been reported in the literature
This paper presents a method for generating the generalized active -compensated
non -inverting v.c.v.s. structures employing
three op -amps. Several novel actively compensated networks are given. The proposed compensated non-inverting amplifiers
have negligible phase and magnitude errors
up to an extended frequency range.
Figure
Resistive
network
Vol
bii
active -compensated non-inverting amplifier

employing three op -amps. The basic circuit
equations are represented by the matrix
equation 1, where ai and bit are real coefficients having magnitudes 51, and A is the
open -loop gain of the op -amp, which for all
practical applications is represented by the
single -pole models, Ai(s)es wti/s, (i = 1,2,3)
and where wt is the gain-bandwith product
TABLE
1.
Class
1
2A
2B
3
The signs of transfer function coefficients

as
+
+
+
+
This generalized compensated non inverting amplifier uses three op -amps. By

writing the transfer function in the form of
an error function and equalizing the s and s2
terms of its numerator and denominator
three classes of phase-compensated amplifier are identified Figs 2 to 5.
Fig.1..
a b for i,j =
22
a3
baa
b12
11313
0
0
0
0
0
0
0
0
1,2,3.
b21
b22
b23
b31
b32
b33
+
+
+
+
o
0
0
+
-
TABLE 2. Compensation conditions, normalized magnitude errcrs, where Ti= (K;+1)/wt;,
Compensation conditions
Class
Fig.2
KI=K2=K+a
Fig.3(a)
K2+1-2 -T3
Fig.3(b)
T1=Z=T3
Ti
2A
op -amps employed in the circuit. From

equations 6 and 7 it follows that b22 = b33 =
b23 b32 = O. Without any loss of generality,
take b32=0 and b234r0. The compensation
conditions for this class are
al__a2__a3
represents the generalized
error function and which ideally must have a

unity magnitude and a zero phase. It is
well-known that to reduce the phase and the
magnitude errors to negligible limits, the
coefficients of the s and s2 terms in the
numerator and denominator (equation 7)
must be identical,4.5
In the next section phase -compensated
non -inverting amplifiers are classified
according to the signs of coefficients ai and
bi1(i,j = 1,2,3).
Class 1 non -inverting amplifiers: In this
class the compensation conditions are independent of the gain-bandwith of the three
Normalized
phase error
4)((.0)
Normalized
magnitude error
y(w)
(K1+1)4/K2KI
-T2T2
i=1, 2,3
41K1+1\4
K2+1
2(K1+1)3
4(K1+1)4
b21
en=(Wt)3arg
E(jo1),1'n= (W`)4(E(jw)-1)
Class 2 amplifiers: Here a, = 1 and a2 = a3 =

b,, = b13 = b3, =b22 = 0 and the compensation conditions are given by:
23b32
1)332
T2
Fig.4
Fig.5
T1K2K3=2K2R3=Ts
(K3+1)
It is assumed that wt1=03,2=0313=031 and w
K2-K3
-1.31(3(K3+
< w1.
2[(KI+1)K2K31'' 4[(KI+1)K2K314
(K1+1)4/K1
(K1+1)s/K12
2b23b32 wt2
12b21 wt1
wt3.
The compensated transfer function for this

class is
1+2psn+2p2sn
T2`(s) -p1+2psn+2p2s,2,+2p3s3
233z
where p=-u12211,33
12 b 21b 33
2B
b3,
and it is thus not necessary to use matched

op -amps with this class of amplifier.
Examining the transfer function for this
class the coefficient signs are obtained and
given in Table 1. Fig. 2 represents a class 1
non -inverting amplifier generated from the
coefficient signs. This circuit is a special case
from the Ceiger-Budak zero second derivative
finite -gain amplifier4 after removing one resistor, also reported in ref. 7. Table 2 includes
the compensation conditions and normalized
compensated phase and magnitude errors
assuming matched op-amps are used. Normalized phase and magnitude errors are
defined as:
andsn=
Ohl
For this class the product b23 b32 must have a

negative sign. Thus two types are defined for
this class and are classified as types 2A and
2B with coefficient signs as given in Table 1.
Fig. 3 represents two circuits which belong
to class 2A and Fig. 4 represents a class 2B
49
Vol
vot
(b)
(a)
Fig.3: class 2A
Fig2: class
circuit. It
is
vol
worth noting that the circuit

a different
reported in reference 3 belongs to

type since it has negative b13 and
cients.
b22
coeffi-
Class 3 amplifier. Fig.5 represents a new

circuit whose properties are given in Tables
l and 2.
It is worth noting that the circuits reported in reference 7 do not belong to either
class 2 or 3 defined in this paper.
Dr Soliman is chairman and professor in the
electrical engineering department of the United Emirates University at AlAin, UAR. He
graduated from Cairo University and received
M.S. and Ph.D. degrees from the University of
Pittsburg.
Fig.4: class 2B
Fig.5: class 3
Equations
The basic circuit equations are represented by the matrix equation
Vol
Vol
b11b12b13
Al
Vol
Vo3
a3
A3
References
1. Budak, A., Peterela, D.M., Frequency limitations of
active filters using operational amplifiers, IEEE Trans.
Circuit Theory vol. CT -19, July 1972, pp.322-328.
2. Soliman, A.M. Ismail, M., Active compensation of
op -amps, IEEE Trans. Circuits and Systems vol. CAS -26,
Feb.1979, pp.112-117.
Reddy, MA., Operational amplifier circuits with variable
phase shift and their application to high -Q active RC
filters and oscillators, IEEE Trans. Circuits and Systems
vol. CAS -23, June 1976, pp.384-389.
Soliman, A.M., A generalized active compensated non inverting vcvs with reduced phase error and wide band with, Proceedings IEEE, vol.67, June 1979, pp.963-965.
Soliman, A.M., Classification and generation of active
compensated non -inverting vcvc building block, Int. J. of
Circuit Theory and Applications, vol.8,1980, pp.395-405.
Natarajan, S., Bhattacharyya, B.B., Design and some
applications of extended bandwith finite gain amplifiers,
J. Franklin Institute, vol.35, June 1978, pp.321-341.
3. Natarajan, S., Bhattacharyya, B.B., Design of actively
compensated finite gain amplifiers for high frequency
applications, IEEE Trans. Circuits and Systems vol.CAS27, Dec.1980, pp.113-1139.
4. Geiger, R., Budak, A, Design of active filters independent of first and second order operational amplifier time
constant effects, IEEE Trans. Circuits and Systems
vol CAS -28, August 1981, pp.749-757.
5. Soliman, A.M., Design of high frequency amplifiers.
IEEE Trans. Circuits and Systems Magazine, vol.5, June
1983, pp.9-11.
Soliman, A.M., Novel phase and magnitude compensated
non -inverting voltage amplifiers. Frequenz, vol.40
(1986)3, pp.71-72.
6. Budak, A., Passive and Active Network Analysis and
Synthesis. Houghton Mifflin. Boston, 1974, p.204.
7. Bhattacharyya, B.B. Lopes, P.B., Classification, generation and evaluation of actively compensated non inverting finite-gain amplifiers, IEEE Proceedings,
vol.131, Oct. 1984, pp.179-189.
50
(1)
b21b22b23
A2
b31b32b33 -
where a, and b,, are real coefficients having magnitudes

1. A, is the open -loop gain of the
op -amp which for all practical applications is represented by the single -pole model (ref.6):
(i=1,2,3)
(2)
where oh is the gain -bandwidth. From equation 1, the generalized expression for the transfer
function of the circuit is
T(s)=Vol=N(s)
V;
13)
D(s)
a1b22+ al
where N(s)=a1g11+a2B21+a3B31+a3b13-a1b33+azb1L
A3
A2
D(5)=-b11B11-b21B21-b31B31+
and
Bl1"+B22+B33AI
A2
A3
B11-b22b33-b23b32
B21=b131332-b12b33
B22=b11b33-b13b31
B33=b11b22-b12b21
b
A2A3
(4)
A2A3
b22
b33
AlA3
AlA2
A1A2A3
(51
B31-b12b23-b13b22
(6)
Using equations 2 to 5, the transfer function of the circuit can be written as:
T(s)=B.E(s)
1+1
E(s)-
where
C=a1B11+a2B21+a3B31,
B=-(b11B11+bz1Bz1+b31B31).
al
w13
w12w13
w12
l(a3613-a1b33+a2b12-a`b22)s+
L
s21
1+11(B11+B22+B33)s+(
B
wt
wt2
wt3
b11
wt2wl3
b22
wtlwt3
b33
ll
1
wtlwt2 1s2+ wllwt2wt3
s1J
(7)
p,Pi
ti2> -s)
.1.
\,o
-R9tet Q
QeaSaee
0
ea-ro
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tcot.
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GataG
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ttzo
`j`r a5% ooto PO ' oat

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51
Fifty years of
computer science
An appraisal of A.M. Turing's paper
"On computable numbers" published in November 1936
TOM IVALL
computer science can be

separated from computer
With the benefit of hindsight

this imaginative concept may
not seem all that remarkable.
If
technology, it can fairly be

said to have started half a century
ago, in November 1936. This was
But those who have lived

through the half century of development of the digital computer appreciate it fully. And
apart from the engineering perspective, Turing's whole idea of
introducing a theoretical but
when a young Cambridge mathematician. Alan Mathison Turing, published his now famous
paper "On computable numbers,
with an application to the Entscheidungsproblem".
Written as a contribution to
pure mathematics, this paper
nevertheless described, as a
central part of its method, the
essentials of the modern, automatic, stored -program digital
computer. Although the arrangement described was a
purely abstract, theoretical computing machine, and Turing
workable machine into a paper

on pure mathematics was quite
novel to the academic establishment of that time. As Norbert
Wiener, the American mathematician, remarked in his book
Cybernetics, Turing was perhaps
"first among those who have
studied the logical possibilities
of the machine as an intellectual
experiment...."
apparently had no engineering
not in any particular form of mechanical or
considerations in mind at that time, it was

nevertheless a feasible system. It had to be,
because a requirement of the paper was to
make concrete in the imagination a finite,
physical construction that would perform
systematically a sequence of logical steps
equivalent to those going on in the mind of a
human computer. It was a sort of 'thought
experiment'. Turing showed that the mental
operations a human can perform can be
analysed into sequences of the very simple
'mechanical' operations that his theoretical
machine was capable of going through.
A highly significant aspect of 'Turing
electrical hardware but in
machines',
as these theoretical
constructions later became known, was that
their internal functioning was entirely
described by groups of symbols. The
concreteness of a Turing machine existed
52
precise,
complete description of its rules of operation
-a "standard description" as Turing calls it a
expressed entirely in letters or numbers.

Rules of operation expressed in symbols
are what we now call instructions, and a
particular selection of these is what we call a
program. Since these rules of operation are
not permanently set in the machine as a
particular arrangement of hardware but can
be altered at will simply by changing the
symbols, the Turing concept was essentially
that of the stored -program computer. It was
Turing who first demonstrated that the
actions of computing machines, as well as
the data processed by these machines, could
be specified in the abstract form of
mathematical symbols. You could say he
invented software.
MATHEMATICAL BACKGROUND
To understand how Turing's paper came to
be written, we have to digress slightly into
the history of the philosophy of pure

mathematics. First, the title of the paper
requires a quick look. Here the process
implied by "computable" means computing
in the broadest sense at that time - as done
mentally by human beings, perhaps with the,
aid of mechanical desk calculators. Forget
electronic computing at this stage. When
Turing refers to a "computer" in his paper he
means a human computer.
The term "computable numbers" in the
title means numbers like it or ewhich can be
computed from well known formulae. More
generally, Turing explains, "The

'computable' numbers may be described
briefly as the real numbers whose
expressions as a decimal are calculable by

finite means... According to my definition, a
number is computable if its decimal can be
written down by a machine." Such numbers
include, for instance, the real parts of all
algebraic numbers.
The term "Entscheidungsproblem" in the
title can be translated as "decision problem".
It was written in German because this was
the name of a particular problem occupying
a group of German mathematicians at the
end of the 19th century. Prominent among
these was David Hilbert (1862-1943). Some
readers may already know him from the
Hilbert transform or the concept of the
Hilbert space (a multidimensional space). In
the paper, Turing refers specifically to the
Machine capable of having
finite
number of
m configurations
J
Head
for reading,
writing
and
erasing
Tope
"Hilbertian Entscheidungsproblem".
Broadly, the Entscheidungsproblem is a
problem in logic: that of finding a definite
method or algorithm that can be relied on to
decide whether a mathematical proposition*
can be proved to be true.
Hilbert was a formalist in his approach to
investigating the fundamental basis of
mathematics. (Other approaches are based
on logic and on intuition.) In other words,
he proposed that mathematics was a kind of
game played with symbols, in accordance
with a set of rules. It should not be regarded
as necessarily true, apart from these formal
considerations.
But the formalist view of mathematics
could be strengthened and validated if the
whole system could be proved to be
internally consistent, that is, free from
contradictions, and complete, in the sense
that every mathematical statement could be
either proved or disproved. This was
Hilbert's `programme', as it was called. He
and a group of other mathematicians
embarked on this project in the early 1900s.
The method adopted for the programme
was to justify the whole of mathematics,
including arithmetic and set theory, by
putting it in a formal system and proving
that this system was self -consistent. This
was to be done by the simplest and most
concrete methods of reasoning.
Mathematical statements were to be

represented by strings of symbols in formal
logic systems. Then proofs were to be given
of a consistency of such systems so that they
would be shown to be correct in describing
meaningful mathematical statements.
But the proofs were the difficulty. A
procedure was necessary to decide whether
consistency (lack of contradiction) was in
fact provable - what was called a decision
procedure. Finding a decision procedure was
called the decision problem, or Entscheidungsproblem. And this had been recognized as a problem in logic since the late
19th century. (Note that George Boole, the
originator of Boolean algebra, had published
his famous book The Law of Thought in
1854.)
But in 1931 Hilbert's programme received
a fatal blow from the now famous Gdel
theorem. The Czech mathematician Kurt
Gdel showed that it is impossible to prove
the consistency of a formal system within
the system itself. Mathematics was not
complete. Every mathematical statement
could not be either proved or disproved.
Tape can be moved to left

or right, one division at o time
Divisions on tape
some containing
symbols, some blank
Fig.1. Essentials of the computing machine described in Turing's paper.

By 1936 the Gdel theorem was, of course, conditions gl,g2,...qR which will be called
well known to Turing. He refers to it in the "m -configurations". The machine is
paper, saying that "conclusions are reached supplied with a "tape" (the analogue of
which are superficially similar to those of paper) running though it, and divided into
Gdel. These results have valuable sections (called "squares') each capable of
applications. In particular it is shown... that bearing a "symbol". At any moment there is
the Hilbertian Entscheidungsproblem can just one square, say the r -th, bearing the
symbol S(r) which is "in the machine". We
have no solution."
Nevertheless it was the Entscheidungs- may call this square the "scanned square".
problem which stimulated Turing to The symbol on the scanned square may be
consider a kind of left -over from the Gdel called the "scanned symbol". The "scanned
theorem: whether there could be some symbol" is the only one of which the
definite procedure for distinguishing machine is, so to speak, "directly aware".
provable from unprovable mathematical However, by altering its m -configuration the
statements. As related by Andrew Hodges in machine can effectively remember some of
an excellent biography of Turing,' this the symbols which it has "seen" (scanned)
happened as a result of his attending a previously. The possible behaviour of the
course of lectures at Cambridge on the machine at any moment is determined by
the m -configuration qn and the scanned
foundations of mathematics.
The lecturer was M.H.A. Newman, who, as symbol S(r). This pair qa, S(r) will be called
it happened, had taken part in an inter- the "configuration": thus the configuration
national conference in 1928 at which Hilbert determines the possible behaviour of the
had renewed his call for a project to machine. In some of the configurations in
investigate the foundations of mathematics which the scanned square is blank (i.e. bears
on a formalist basis. Hilbert's notion that no symbol) the machine writes down a new
there might be a definite method for testing symbol on the scanned square: in other
mathematical statements, as discussed configurations it erases the scanned symbol.
above, was interpreted by Newman as the The machine may also change the square
possibility of a "mechanical process" that which is being scanned, but only by shifting
it one place to right or left. In addition to any
would churn out answers.
This idea of a possible mechanical process of these operations the m -configuration may
apparently became firmly lodged in Turing's be changed. Some of the symbols written
mind. It started him thinking specifically down will form the sequence of figures
which is the decimal of the real number
about machines that manipulate symbols
for example, typewriters. He conceived a which is being computed. The others are just
computational answer to Hilbert's decision rough notes to "assist the memory". It will
problem in 1935, when he was only 23, and only be these rough notes which will be
this led to the writing of his paper "On liable to erasure.
It is my contention that these operations
computable numbers" in the ensuing
include all those which are used in the
months.
computation of a number. The defence of
this contention will be easier when the
TURING MACHINES
theory of the machines is familiar to the
Figure 1 shows the essentials of a Turing reader.
machine (though there is no such diagram
Turing then goes on to say that he is
in the paper itself). This is described by concerned specifically with automatic
Turing as follows:
machines. He defines an automatic
We may compare a man in the process of computing machine as one in which its
computing a real number to a machine motion at each stage "is completely
which is only capable of a finite number of determined by the configuration.." (in the
53
Pilot model of the ACE computer built at the NPL as an outcome of Turing's work there. A part of this machine can be seen at the Science
Museum, South Kensington, London. (Crown copyright)
above sense). The complete configuration at

any stage is described by the number of the
scanned square, the complete sequence of all
symbols on the tape, and the m configuration. In other words it is the

information itself which pushes the machine
along - not some external agency - so that it
becomes automatic.
Then Turing explains that the behaviour
of such an automatic machine can be
described by successive rows of symbols and
abbreviations in a table. This table has the
column headings:
m
configuration
symbol
operations
final m
configuration
The first column contains code letters: the

next contains tape symbols as defined above.
The 'operations' column contains

abbreviations like 'R' which means the
machine moves one tape square to the right
and scans that square. The 'final mconfiguration' column contains code letters
belonging to the same alphabet as in the first
column and having the same meanings.
In each row of the table the first two
columns describe a machine configuration.
For this, the operations indicated in the
third column are performed in succession
and the machine moves into the final m configuration in the last column. In the
context of the paper, this table is the
machine.
Turing then gives examples of how
different machines based on this general
principle can be mentally constructed to
compute different sequences of digits. He
actually uses the binary digits 0 and 1 in the
54
examples, but this has nothing whatever to

do with the fact that binary notation was
later used in practical computers to suit
two -state electrical and electronic devices.
MACHINE ACTIONS AS NUMBERS

After mentioning that the m -configuration
tables can be abbreviated for convenience in
performing frequently used, standard
processes, the paper goes on to demonstrate
that the rows of a table can be encoded as
letters of the alphabet. A group of these code
letters is a "standard description" of a

machine. What this describes is not some
arrangement of hardware but the rules of
operation of the machine.
Finally, Turing says, the letters can be
further encoded into decimal digits. As a
result "we shall have a description of the
machine in the form of an arabic numeral.
The integer represented by this numeral
may be called a description number... of the
machine." It determines the standard
description and the structure of the machine
uniquely. Further, there is a description
number for each computable sequence.
Thus at this point the paper is dealing with
certain computing machines (`Turing
machines') which are automatic and have
input, output and memory. This kind of
machine has an instruction code in the sense
that a given machine action is determined by
a code consisting of a symbol on the tape and
symbols representing the current machine
configuration. It has a program
though
fixed and not an alterable stored program in
today's sense
in that it carries out an
ordered sequence of steps to perform a

computation. But so far these machines are
special-purpose ones: each is mentally
constructed to compute one particular
sequence and that alone.
UNIVERSAL TURING MACHINES

The crucial point about the special-purpose
machines is that each machine is completely
described
that is, everything it does in
computing its particular sequence
by a
code number: its description number. Thus
machine operations are encoded
as
numbers, and as far as the machine is

concerned there is no distinction between
the numbers of the sequence being
computed and the operations performed on
those numbers: they are all just symbols.
Through these operation numbers the tables
can be put on the tape.
But in addition to the particular specialpurpose machines described, a table could.
represent the behaviour of any machine. It
follows that a single, general-purpose
Turing machine could be made to simulate
the actions of a variety of other, specialpurpose machines. Turing calls this allpurpose device a "universal computing
machine". It is possible, he says, "to invent a
single machine which can be used to
compute any computable sequence." If this
machine is supplied with a tape at the start of
which is written the standard description of
some particular computing machine then it
will compute the same sequence as the
particular machine.
In elaborating this general idea the paper
goes on to say that the universal computing

machine would have the rules of operation of
the special-purpose machine written

somewhere inside it. Then "each step could
be carried out by referring to these rules." In
modern terminology, the universal
computing machines has a stored program.

And the concept of such a stored program
introduced by the words
"We have only to regard the rules as being
capable of being taken out and exchanged for
others..." Remembering that the rules are
expressed as symbols, we see that Turing is
here talking about what we now call
software. There follows a detailed account of
the universal computing machine, all in
terms of symbols in tabular form.
being alterable
is
MATHEMATICAL CONCLUSION
The second half of Turing's 36 -page paper is
devoted to its main mathematical purpose:
to prove that there is a class of quite
elementary arithmetical questions for which
there is no decision procedure. As the author
states, the results obtained in the paper "can
be used to show that the Hilbertian Ent -t
scheidungsproblem can have no solution."
Having given a proof of this, he concludes:
"Hence the Entscheidungsproblem cannot
be solved."
LATER DEVELOPMENTS
Despite the purely abstract nature of the.
computing machines discussed in the paper,
Turing did go on in later years to build
experimental electrical and electronic systems for mathematical purposes. Moreover,
during the course of his brilliant code
decipherment work at the Government Code
and Cypher School in the 1939-45 war he
was in close contact with the building and
operational use of the Colossus, an electronic cryptanalytic machine constructed with
thermionic valves. As a result he acquired a
certain amount of electronic engineering
knowledge.
He learnt even more about the possibilities and limitations of the current electronics technology when he joined the then
new Mathematics Division of the National
Physical Laboratory at Teddington. He had
been invited there specifically to work on a
project officially described as "Investigation
of the possible adaptation of automatic telephone equipment to scientific r.),nputing"
and "Development of electronic counting
device suitable for rapid computing." The
Division was familiar with Turing's 1936
paper. It was also very much aware of
current American work in computing
machines, such as the Automatic Sequence
Controlled Calculator at Harvard University
and the ENIAC (Electronic Numerical Integrator and Calculator) at Pennsylvania University.
At the NPL Turing worked for three years
on its computing project, producing what
became in effect a specification for the ACE
(Automatic Computing Engine). This was
eventually built, first as the Pilot ACE and
later, in 1958, as a full-scale machine.
Meanwhile Turing moved to Manchester
University to do similar work there. The
Pilot ACE was later produced in commercial
form by English Electric under the name

DEUCE, while Manchester University's
machine was similarly developed into the
Ferranti Mark I computer. So Turing played
some part in the research which led to the
founding of the British computer industry.
There has been a good deal of discussion
about the relative contributions of Turing
and von Neumann to the concept of the
stored program digital computer. It was
John von Neumann, the Hungarian American mathematician, who became an

adviser to the ENIAC project and was associated with the idea of introducing a stored
program to replace the ENIAC's original
plug -and-socket method of setting up instructions. Von Neumann and Turing knew
each other. They were together for a while at
Princeton University and had discussions
there. Furthermore von Neumann had read
and was aware of the significance of Turing's
1936 paper. Commentators have therefore
suggested that Turing's paper provided the
fundamental idea of a program stored as
symbols which von Neumann later picked up
and utilized, consciously or unconciously,
for a practical purpose.
For example, Donald Davies of the NPL
has written: "Probably few of the early
pioneers had read the remarkable paper
(Turing's) but without doubt one man knew
it and understood fully its significance John von Neumann. His comments to Eckert and Mauchly when he first saw ENIAC,
and afterwards his own work with Goldstine,
led to the flowering of the stored program
computer in the USA, while in Britain
several influences were at work and one
influence was Turing himself."4.
Other authorities hold that von Neumann
was the direct originator of the stored-.
program concept, and probably from this
view comes the term "von Neumann
architecture' in general use today. Indeed it
is so firmly established that departures from
the principle are now being called `Non -von'
computers.
But this discussion about priority in no
way diminishes the fact of Turing's 1936
paper and its undoubted originality. Perhaps
the only way to assess its significance and
contribution to present-day computer
science/technology is to read it onself and
make up one's own mind.
111111111ea111V.m.rRtINrield.11eiu,rrillIlletyMen11111
ELECTRONICS
& WIRELESS WORLD
Two-
dimensional
Fourier
transform
Hard-disc
interface
6N000 family
Data
encrypt ion
Time dilation
Synthesized
I. f. waveforms
Measuring
settling time
Equipment
housing
NEXT
MONTH..
Two-dimensional
Fourier Transform
Weysel Orner follows up his article in the
June issue and describes the

transformation of two-dimensional data on
the BBC computer. The results can be
applied to image processing in applications
such as LANDSAT image analysis,
magnetic resonance imaging and filter
design.
Electronic encryption
Brian McArdle explains the protection of
data using the US Data Encryption
Standard and describes interfacing
between a DES i.c. and a Z80
microprocessor
Hard disc interface

Byte -for -byte, hard -disc storage is around
ten times cheaper than floppy -disc storage.
John Adams discusses interfacing a hard disc drive to a microcomputer with the
aid of a practical example.
References
Turing, "On computable numbers, with an
application to the Entscheidungsproblem", Proc.
Lond. Math. Soc. (Series 2), 42, Nov. 12, 1936, pp.
230-265.
2. K. Gdel, "Ober formalunentscheidbare Stze
der Principia Mathematica und verwandter Systeme, 1", Monatshefte Math. Phys., 38, 1931, pp.
1. A.M.
173-198.
3. A. Hodges, Alan Turing, The Enigma of Intelligence, Unwin Paperbacks, London, 1985.
4. Quoted from a foreword by D. W. Davies to a
reprint of Turing's original proposal to build a
computer at NPL; from a report on a discussion on
"The Foundations of Computer Engineering" in
The Radio and Electronic Engineer, Golden
Jubilee issue, 45, No. 10, Oct. 1975, pp. 598-602.
68000 processor family

Descriptions of the 68020 coprocessor
interface and pipelining are included in
David Burn's overview of the 68000 -series
16/32 bit microprocessors
Equipment enclosures
There is a vast range of cases, racking and
boxes in which to house electronic
equipment. If you need a 'reach-me-down'
enclosure and have no house -style
requirements, our survey will assist in
making a choice.
55
1al Hous:
IcOIVIPUTER
DON'T MISS THE CPM Deal

OF the CE TURY
*4. DISTEL
The ORIGINAL FREE OF CHARGE dial up data

base. Buy, browse or place YOUR OWN AD for
goods or services to sell. 1000's of stock items,
spares and one off bargains Updated daily.
ON LINE NOW. CCITT, 8 bit word, no parity.
For 300 baud modems call 01-679 1888
For 1200-75 baud modems call 01-679 6183
Your monitor from its computer!! For
only 24.95 it becomes a SUPERB
HIGH QUALITY COLOUR TV SET
FREE
The fabulous TELEBOX an INVALUABLE MUST for the owner of

ANY video monitor with a composite input colour or monochrome
Made by a major UK Co as a TOP QUALITY, stand alone UHF
tuner and costing OVER 75 to manufacture, this opportunity to
give your monitor a DUAL FUNCTION must not be missed! The
TELEBOX consists of a compact, stylish two tone charcoal
moulded case containing ALL electronics tuner, power supply etc
to simply plug in and convert your previously dedicated computer
monitor into a HIGH QUALITY COLOUR' TV SET, giving a real
benefit to ALL the family!! Don't worry if your monitor doesn't have
sound- THE TELEBOX even hasan integral4 watt audio amplifier
for driving an external speaker. PLUS an auxiliaryoutput for superb
quality television sound via your headphones or HI Fl system etc
Other features include: Compact dimensions of only 15.75' w x
7.5 d x 3.5 h latest technology. BRITISH manufacture, fully tuneable7 channel push button tuner, AutoAGC circuit SAW filter,
LED status indicator, fully isolated 240v AC power supply for total
safety, Mains ON-OFF switch etc Many other uses
LIMITED QUANTITY- DON'T MISS THIS OFFER!!!
The FABULSU CPM TATUNG PC2000

Professional Business System
A cancelled export order and months of negotiation enables us to offer this professional
PC. CPM system, recently on sale at OVER 1400, at a SCOOP price lust over the cost of
the two internal disk drives!' Or less than the price of a dumb terminal!'
Not a toy. the BIG BROTHER of the EINSTIEN computer, the DUAL PROCESSOR
PC2000 comprises a modern stylish three piece system with ALL the necessities for the
SMALL BUSINESS, INDUSTRIAL, EDUCATIONAL or HOBBYIST USER. Used with
the THOUSANDS of proven, tested and available CPM software packages such as
WORDSTAR, FAST, DBASE2 etc. the PC2000 specification, at our prices. CANNOT
BE BEATEN"
The central processor plinth contains the 64K, Z80A processor, DUAL TEAC 55F 5'/:'
Double sided 40/80 track disk drives (1 Mb per drivel, PSU, 4K of memory mapped screen RAM, disk controller, RS232,
CENTRONICS and system expansion ports and if that's not enough a ready to plug intoSTANDARD8" DRIVE port for up to FOUR
8' disk drives either in double density or IBM format The ultra slim 92 key, detachable keyboard features32 user definable keys,
numeric keypad and text editing keys even its own integral microprocessor which allows the main Z80A to devote ALL its time to
USER programs eliminating "lost character" problems found on other machines The attractive, detachable 12" monitor combines
a green anti-glare etched screen with full swivel and tilt movement for maximum user comfort Supplied BRAND NEW with CPM
2.2. user manuals and full 90 day guarantee. Full data sheet and info on request
PC2000 Wordprocessor System
PC2000 System
PC2000 Business System with CPM
with CPM and TEC FP25 daisywheel
with CPM Etc.
and 'Ready to Run' FAST Sales and
printer
COST OVER 1400
Purchase ledger, supports up to
9000 Accounts, VAT etc.
COST OVER 1700
NW
O
NOW only
Z399
NOW only 499

Carnage 8 Insuranc
SURPLUS SPECIALS ON
ONLY 24.95 OR 19.95 if purchased with ANY of our
video monitors Supplied BRAND NEW with full instructions and 2 YEAR PRESTEL - VIEWDATA - TELEX
warranty. Post and packing 3.50
'When used with colour crt
MONOCHROME
MONITOR SPECIALS
COLOUR
'SYSTEM ALPHA' 14" COLOUR MULTI INPUT MONITOR

Made by the famous REDIFFUSION Co. for their own professional computer
system this monitor has all the features to suit your immediate and future
requirements Two video inputs RGB and PAL Composite Video, allow direct
connection to BBC/IBM and most other makes of micro computers or VCR's,
including our very own TELEBOX An internal speaker and audio amp may be
connected to computer or VCR for superior sound quality. Many other features:
PIL tube, Matching BBC case colour, Major controls on front panel Separate
Contrast and Brightness - even in RGB mode Separate Colour and audio
controls for Composite Video input BNC plug for composite input 15 way 'D'
plug for RGB input modular construction etcetc
This Must Be ONE OF THE YEAR'S BEST BUYS. PC USER
Supplied BRAND NEW and BOXED, complete with DATA and 90 day
guarantee ONLY 149,00 as above OR IBM PC Version 165.00
15 Day 'D skt 1.00, BNC skt 75p BBC interface cable 5.50
DECCA 8016" COLOUR monitor. RGB input.
Little or hardly used manufacturer's surplus enables us to offer this special
converted DECCA RGB Colour Video TV Monitor at a super low price of only
99.00, a price for a colour monitor as yet unheard oft! Our own interface
safety modification and special 16" high definition PIL tube coupled with the
DECCA 80 series TV chassis give 80 column definition and quality found only
on monitors costing 3 TIMES OUR PRICE. The quality for the price has to be
seen to be believed! Supplied complete and ready to plug direct to a BBC
MICRO computer or any other system with a TTL RGB output Other features
are: in'ernal speaker, modular construction, auto degaussing circuit, attractive
TEAK CASE, compact dimensions only 52cm W x 34 H x 24 D, 90 day
guarantee Although used units are supplied in EXCELLENT condition.
ONLY 99.00 + Carriage.
DECCA 80 16" COLOUR monitor. Composite video input Same as above
model but fitted with Composite Video input and audio amp for COMPUTER,
VCR or AUDIO VISUAL use ONLY 99.00 + Carr.
REDIFFUSION MARK 3, 20" COLOUR monitor. Fitted with standard 75 ohm
composite video input and sound amp This large screen colour display is ideal
for SCHOOLS, SHOPDS, DISCOS, CLUBS and other AUDIO VISUAL applications Supplied in AS NEW or little used condition ONLY 145.00 +.Carr.
BUDGET RANGE EX EQUIPMENT MONOCHROME video monitors.
All units are fully cased and set for 240v standard working with composite video
inputs Units are pre tested and set up for up to 80 column use. Even when
MINOR screen burns exist - normal data displays are unaffected 30 day
guarantee
12 KGM 320-1 B/W bandwidth input will display up to 132 x 25 lines 32.95
12 GREEN SCREEN version of KGM 320-1. Only 39.95
9 KGM 324 GREEN SCREEN fully cased very compact unit Only 49.00
Carriage and insurance on all monitors 10.00
P
GOULD OF443 enclosed, compact switch mode supply with DC regulated

outputs of +5v @ 55a. +12v @ 0.5a, -12v @ 0.1a and -23v @ 0.02a. Dim 18 x
11 x 6 cm 110 or 240v input. BRAND NEW only 16.95
GOULD G8 -40A 5v 40 amp switch mode supply NEW 130.00
AC -DC Linear PSU for DISK drive and SYSTEM applications. Constructed on a
rugged ALLOY chassis to continuously supply fully regulated DC outputs of +5v
@ 3 amps, -5v @ 0.6 amps and +24v @ 5 amps Short circuit and overvoltage
protected. 100 or 240v AC input. Dim 28 x 12.5 x 7 cm NEW 49.94
Crriage on
all PSU's
300
i:442.11:1:1)11
Manufacturer's BRAND NEW surplus

DEC LA34 Uncoded keyboard with 67 'quality gold plated switches on X-Y
matrix- ideal micro conversions etc 24.95
AMKEY MPNK-114 Superb word processor chassis keyboard on. single PCB
with 116 keys Many features such as On board Micro, Single 5v rail full ASCII
coded character set with 31 function keys numeric keypad cursor pad
and 9600 baud SERIAL TTL ASCII OUTPUT!! Less than half price
Only 89.00 with data Carriage on Keyboards 3.50
56
.'
THE ALLADINS CAVE OF COMPUTER AND ELECTRONIC EQUIPMENT

NOT LINE DATA VASE
1000s OF
BARGAINS
FOR CALL
,l
..._
-_
only 99.00
DECCAFAX VP1 complete Professional PRESTEL

system in siimline desk top unit containing Modem.
Numeric keypad. CPU. PSU etc. Connects direct to
standard RGB colour monitor. Many other features
include: Printer output. Full keyboard input. Cassette
port etc. BRAND NEW with DATA. A FRACTION OF
COST only 55.00
ALPHATANTEL. Very compact unit with integral FULL
ALPHA NUMERIC keyboard. Just add a domestic TV
receiver and you have a superb PRESTEL system and
via PRESTEL the cheapest TELEX service to be
found" Many features: CENTRONICS Printer output.
Memory dialling etc. Supplied complete with data and
DIY mod for RGB or Composite video outputs. AS
NEW only 125.00
Post and packing on all PRESTEL units 8.50
EX-STOCK INTEGRATED CIRCUITS

4164 200 ns D RAMS 9 for 11 4116 os
1.50 2112 10.00 2114 2.50 2102 2.00
6116 2.50 EPROMS 2716 4.50 2732 3.00
2764 4.95 27128 5.50 6800 2.50 6821
68A09 8 6BB09 10 8085A 5.50 8086 15
8088 8 NEC765 8 WD2793 28 8202A
22 8251 7 8748 15 280A DART 6.50
Z80A CPU 2.00. Thousands of IC's EX STOCK
1
send SAE for list.
DISK DRIVES
Japanese 51/4" half height 80 track double sided disk
drives by TEAC. CANON, TOSHIBA etc
Sold as NEW with 90 day guarantee ONLY 85.00
TEC FB303 Double sided HH 40 TRK NEW 75.00
SUGART SA400 SS FH 35 TRK 55.00
SIEMENS FDD100 SS FH 40 TRK 65.00
carriage on 51/4" drives 5.50
Brand NEW metal 5'/.e DISK CASES with internal PSU.
DSKC1 for 2 HH or FH drive
29.95 +pp 4.00
DSKC 2 for HH drive
22.95 +pp 3.50
OKSC 3 As DSK1 LESS PSU
12.95 +pp 2.50
DSKC 4 As DSK2 LESS PSU
10.95 +pp 2.00
8" IBM format TESTED EX EQUIPMENT.
SHUGART 800/801 SS
175.00 +pp 8.50
SHUGART851 DS
250.00 +pp8.50
TWIN SHUGART851's2 Mb total capacity in smart case
complete with PSU etc
595.00
MITSUBISHI M2894-838" DS Mb equiv. to SHUGART
SA85OR. BRAND NEW at 275.00
+pp 8.50
DYSAN 8" Alignment disk
29.00 + pp 1.00
Various disk drive PSLrs Ex Stock SEE PSU section.
HARD DISK DRIVES
DRE/DIABLO Series 30 2.5 Mb front load
525.00
Exchangeable version 295.00. ME3029 PSU 95.00
DIABLO44/DRE4000A, B 5+5 Mb from 750.00
CDC HAWK5+5 Mb795.00. CDC 978280 MbRMO3
etc
00.
PERTEC D34225+5 Mb
405.00
RODIME 5'/a" Winchesters ex -stock from 150 CALL
Clearance items- Sold as seen - No guarantee
ICL 2314 BRAND NEW 14" Mb Removable pack hard
disk drive, cost over2000 with data
ONLY 99.00
BASF 8172 8" 23Mb Winchesters
199.00
Unless stated,all drives are refurbished with 90 day
guarantee Many other drives and spares in stock- call
sales office for details
MODEMS
Join the communications revolution with our super

range of DATA MODEMS, prices and specifications
to suit all applications and budgets......
BRAND NEW State of the art products
DACOM DSL2123 Multi standard 300-300, 1200-75
Auto answer etc
268.00
DACOM DSL2123A0 Auto dial, smart modem with
multi standard AUTO SPEED detect and data buffer
with flow control etc
385.00
DACOM DSL2123GT The CREAM of the intelligent
modems,
auto dial, auto call index. buffer
etc etc
Steebeck SB1212 V22 1200 baud FULL
sync or asyrlc optional auto dial
TRANSDATA 307A Acoustic coupler 300
duplex originate only, RS232 interlace
498.00
DUPLEX
465.00
baud full
49.00
BRITISH TELECOM full spec CCITT, ruggedised

bargain offers Sold TESTED with data Will work on
Ex
any MICRO or system with RS232 interface.

MODEM 13A 300 baud unit only 2" high fits under
phone CALL mode only
45.00_
MODEM 20-1. 75-1200 baud. Compact unit for use
as subscriber end to PRESTEL TELECOM GOLD,
MICRONET etc
39.95 +pp6.50
MODEM 20-2 1200-75 baud Same as 20-1 but for
computer end
85.00 +pp 6.50
DATEL 2412. Made by SE Labs for BT this two part
unit is for synchronous data links at 1200 or 2400
baud using 2780/37P0 protocol etc Many features
include 2 or 4 wire working self test auto answer etc
COST OVER 800. Ojr price ONLY 199 +pp 8.00
DATEL 4800, RACAL MPS4800 baud modern EX
BT good working order, ONLY 295.00 +pp 8.00
SPECIAL OFFER
MODEM TG2393. Ex BT, up to 1200 baud full

duplex 4 wire or half duplex over 2 wire line. ONLY
85.00 PER PAIR +pp 10.00
For more information contact our Sales Office.
MATRIX PR
SPECIAL BULK PURCHASE of these compact high

speed matrix printers Built in Japan for the Hazeltine
Corporation this unit features quality construction
giving 10ocps bidirectional, full pin addressable
graphics, 6 type fonts. up to 9 5 single sheet or
tractor paper handling, RS232 and CENTRONICS
parallel interface Many other features BRAND NEW
and BOXED. COST 420 Our price Only 199.00
Dry Fit MAINTENANCE FREE by Sonnenschein

& Yuasa.
A300 07191315 12v 3Ah NEW
13.95
A300 07191312 6v 3Ah NEW
9.95
A300 071 91 202 6-0-6v 8Ah TESTED Ex
1
Equip 5.99
VDU TE ' MINALS
Standard VDU data entry terminals

at give away prices)!
OUME OVT108. Current product, state of the art
terminal with detachable keyboard, 12 Green screen,
2 page RAM, TVI 925. Hazeltine, ADMSA emulations,
software setup, 25 x 80, Clock Swivel and tilt base,
Printer port, Function keys etc. BRAND NEW and
BOXED AT ALMOST HALF PRICE Only 425.00
AJ510 - EX RENTAL, Z80 controlled, 15 green
screen 24 x 80 display, graphics, cursor addressing,
printer port etc. Very good condition TESTED complete
with manual only 225.00
ADDS 520 - Dumb terminal, used, 12" b/w screen
interface and printer port.
TESTED.
RS232
ONLY 125.00. Carriage on terminals 10.00
100's of other terminals in stock. CALL for more details.
All prices quoted are for U.K. Mainland, paid cash with order in Pounds Sterling PLUS VAT. Minimum order value 2.00.
CT
i I1\1 Uii11v11iI' r_I -
1_I l
1_ I_
PLESSEY VUTEL, ultra compact unit, slightly larger

a telephone features A STANDARD
DTMF
TELEPHONE (tone dial) with 5 CPT monitor and
integral modem etc for direct connection to PRESTEL
VIEWDATA etc. Designed to sell to the EXECUTIVE at
over 600" Our price BRAND NEW AND BOXED at
than
Minimum Credit CardorderEl0.00. Minimum BONA FIDE account ordersfrom Government Depts., Schools, Universities and
established companiesE20,00. Where post and packing not indicated please ADD 1.00 + VAT. Warehouse open Mon -Fri
9.30-5.30. Sat 10.30-5.30. We reserve the right to change prices and specifications without notice. Trade, Bulk and Export
32 Biggin Way, Upper Norwood, London SE19 3XF

Telephone 01-679 4414 Telex 894502 Data 01-679 1 888
ERS
PRINTERS
- PRINTERS - PRINTERS
ASS
SUPER DEAL? NO - SUPER STEAL TELETYPE

THE FABULOUS 25 CPS "TEC STARWRITER"
/// 7//////////
Made to the very

highest spec the TEC
STARWRITER
FPI 500.25 features a
very heavy duty die cast
chassis and DIABLO
type print mechanism
giving superb
registration and print
a fraction of its
quality. Microprocessor
on ginal cost.
electronics offer full
DIABLO/QUME command compatability and lull con ro via CPM WORDSTAR
ETC. Many other features include bi-directional printing, switchable 10 or 12 pitch.
full width 381 mm paper handling with up to 163 characters per line, friction feed
rollers for single sheet or continuous paper, internal buffer, standard RS232 serial
interface with handshake. Supplied absolutely BRAND NEW with 90 day guarantee
and FREE daisy wheel and dust cover. Order NOW or contact sales office for more
information. Optional extras RS232 data cable 10.00. Tech manual 7.50. Tractor
Feed 140.00. Spare daisy wheel 3.50. Carriage & Ins. (UK Mainland) 10.00.
NOW ONLY 499 + VAT
DIY PRINTER MEN!

Brand New surplus of this professional printer chassis gives an
outstanding opportunity for the Student, Hobbyist or Robotics
constructor to build a printer - plotter - digitiser etc, entirely to their
own specification. The printer mechanism is supplied ready built,
aligned and pre tested but WITHOUT electronics. Many features
include all metal chassis, phosphor bronze bearings, 132 character
optical shaft position encoder, NINE needle head, 2 x two phase 12V
stepper motors for carriage and paper control, 9.5" Paper platten etc.
etc. Even a manufacturer's print sample to show the unit's capabilities!!
Overall dimensions 40 cm x 12 cm x 21 cm.
,Sold BRAND NEW at a FRACTION of cost ONLY 49.50 + pp 4.50.
DATA
Industry standard, combined ASCII

110 baud printer, keyboard and 8
hole paper tape punch and reader.
Standard RS232 serial interface.
Ideal as cheap hard copy unit
or tape prep. for CNC and NC
machines. TESTED and in good
condition. Only 250.00 floor
stand 10.00. Carr & Ins. 15.00.
EX NEWS
SERVICE PRINTERS
Compact ultra reliable quality built unit
made by the USA EXTEL Corporation.
Often seen in major Hotels printing up to
the minute News and Financial information, the unit operates on 5 UNIT
BAUDOT CODE from a Current loop,
RS232 or TTL serial interface. 'May be
connected to your micro as a low cost
printer or via a simple interface and filter
to any communications receiver to
enable printing of worldwide NEWS,
TELEX and RTTY services.
Supplied TESTED in second hand
condition complete with DATA, 50 and
75 baud xtals and large paper roll.
TYPE AE11
50 Column
Spare paper roll for AE
TYPE AF11 R 72 Col.
+ Ribbon
TYPE AH11 R 80 Col.
ONLY 49.95
1
4.50
65.00
ASCII/BAUDOT
185.00
Carriage and Insurance 7.50
20,000 FEET OF ELECTRONIC

AND COMPUTER GOODIES
PDP 1140 System comprising of CPU, 124k

memory 8 MMU 15 line RS232 interface.
RP62 40 MB hard disk drive.
TWO 9 track 800 BPI Mag tape drive, dual
track system. VT52 VDU, etc. etc. Tested and
running.
3,750.00
BA11-MB 3.5" Box, PSU, LTC
395.00
DH11-AD 16" x RS232 DMA
interface
1,900.00
DLV11-J4 x EIA interface
350.00
DLV11-E Serial. Modem support
190.00
DUP11 Synch. Serial data i/o
650.00
DQ200 Dilog - multi RK controller 495.00
DZ11-B 8 line RS232 mux board 650.00
KDF11-B M8189 PDP 1123
PLUS
1,100.00
L30 Printer and Keyboard
80.00
LA36 Decwriter EIA or
20 mA loop
270.00
MS11-JP Unibus 32kb Ram
80.00
MS11-LB Unibus 128kb Ram
450.00
MS11-LD Unibus 256kb Ram
850.00
PDP11 /05 Cpu Ram, i/o etc
450.00
PDP11/40 Cpl. 124kMMU
1,850.00
RT11 ver 3B documentation kit
70.00
RK05-J 2.5 Mb disk drives
650.00
KL8 JA PDP 8 async i/o
175.00
M18E PDP 8 Bootstrap option
75.00
VT50 VDU and Keyboard
- 20 mA
VT52 VDU and RS232 interface
MAG TAPE DRIVES

Many EX STOCK computer tape drives and spares by
PERTEC, CIPHER, WANGO, DIGIDATA, KENNEDY
etc. Special offer this month on DEI Cartridge tape
drives ONLY 450.00 each.
CALL FOR DETAILS
COMPUTER/SYSTEM CABINET & PSU

All in one quality computer cabinet with integral
switched mode PSU, mains filtering, and twin fan
cooling. Originally made for the famous DEC PDP8

computer system costing thousands of pounds.
Made to run 24 hours per day the psu is fully
screened and will deliver a massive +5v DC at 17 amps, +15v DC at
1 amp and -15v DC at 5 amps. The complete unit is fully enclosed
with removable top lid, filtering, trip switch, power and run leds
mounted on ali front panel, rear cable entries, etc. etc. Units are in
good but used condition - supplied for 240v operation complete with
full circuit and tech. man. Give your system that professional finish
for only 49.95 + carr. 19" wide 16" deep 10.5" high. Useable area
16" w 10.5"h 11.5"d.
Also available less psu, with fails etc. Internal dim. 19"w, 16"d, 10.5"h.
19.95. Carriage 8.75
DISCOUNT
175.00
250.00
Give your VT100 a Birthday!!!

Brand New VT100 Keyboards
only 85.00
1000's OF EX STOCK spares for PDP8, PDP8A

PDP11, PD P1134 etc. SAE. for list. or CALL
sales office for details.
ALL TYPES OF COMPUTER EQUIPMENT AND
SPARES WANTED FOR PROMPT CASH
PAYMENT.
ON
ELECTRONIC
NTS
EQUIPMEENT
Due to our massive bulk purchasing programme, which enables us to bring you the
best possible bargains, we have thousands of ICs, Transistors. Relays, Caps. PCBs.
Sub -assemblies, Switches etc. etc. surplus to OUR requirements. Because we don't
have sufficient stocks of any one item to include in our ads we are packing all these
items into the BARGAIN OF A LIFETIME. Thousands of components at giveaway
prices. Guaranteed to be worth at least 3 times what you pay. Unbeatable value and
perhaps one of the most consistently useful items you will every buy!!! Sold by
weight.
2.5kIs 5.25 + pp 1.25

1 OkIs 11 .25 + pp 2.25
massive purchase of these desk top

printer terminals enables us to offer you
these quality 30 or 120 cps printers
at a SUPER LOW PRICE against their
original cost of over 1000
Unit
comprises of full OWERTY. electronic
keyboard and printer meth with print
face similar to correspondence quality
typewriter Variable forms tractor unit
enables full width - up to 13.5 120
column paper. upper - lower case.
standard RS232 serial interface. internal
vertical and horizontal tab settings.
standard
ribbon.
adjustable
baud
rates. quiet operation plus many other
features. Supplied complete with manual.
Guaranteed working GE30 130.00.
A
GE1200 120 cps 175.00

Untested GE30 65.00 Optional floor
stand 12.50. Carr 8 Ins. 10 00
SEMICONDUCTOR
'GRAB BAGS'
Mixed Semis amazing value contents
include transistors digital, linear. IC's.
triacs. diodes. bridge recs. etc. etc
All devices guaranteed brand new full
spec with manufacturer's markings. fully
guaranteed.
50+ 2.95 100+ 5.15
TTL 74 Series. A gigantic purchase of an

"across the board" range of 74 TTL series
IC's enables us to offer 100+ mixed
"mostly TTL" grab bags at a price which
two or three chips in the bag would
normally cost to buy. Fully guaranteed all
IC's full spec. 100+ 6.90,
200+ 12.30, 300+ 19.50
ENGLAND'S LARGEST SURPLUS STORE- SEEING IS BELIEVING!
DEC CORNER
GE TERMIPRINTER
I/O TERMINALS
5 kls 6.90 + 1.80

20kIs 19.50 + pp 4.75
MAINS FILTERS
CURE those unnerving hang ups and data
glitches caused by mains interference with
professional quality filters. SD5A matchbox size up to 1000 watt 240 V
Load ONLY 5.95. L12127 compact
completely cased unit with 3 pin fitted
socket up to 750 watts ONLY 9.99.
EPROM COPIERS
The amazing SOFTY 2 The "Complete
Toolkit" for copying. writing, modifying and
listing EPROMS of the 2516, 2716.
2532, 2732 range. Many other functions
include integrai keyboard. cassette interface. serial and parallel i/o UHF modulator
ZIF socket etc.
ONLY 195.00 + pp 2.50.
"GANG OF EIGHT' ' intelligent Z80
controlled 8 gang programmer for ALL
single 5v rail EPROMS up to 27128. Will
copy 8 27128 in ONLY 3 MINUTES. Internal
LCD display and checking routines for
IDIO3.T
operation. Only 395.00 +
pp
00.PROOF
"GANG OF EIGHT PLUS" Same spec. as
above but with additional RS232 serial
interface for down line loading data from
computer etc. ONLY 445.00 + pp 3.00
Data sheets on request
COOLING
Fen
Keep your hot parts COOL and RELIABLE with our range of
COLING FANS ETRI 126LF21 240v 5 blade equipment Ian
Dim. 80
38mm r9 95. ETRI 99XU01 240v Sl,mline
80
Dim 92 x 92
25m,,, equipment glen, NEW E9.95.
GOULD JB-3AR Dim 3'
3' rr 2.5' compact very quiet
runnIng 240v operation. NEW E6.95. MUFFINCENTAUR38mm tans Order 110v OR
BOXER standard 120
120
240v. 3 or 5 blade, NEW at E10.50 or tested EX EQUIPMENT
C5.50, Low Voltage DC Fans BUHLER 69.11.22. 8 16v DC
micro
a,ature reversible. Uses brushless servo motor.
i
almost silent
running,`guaranteed 10.000 hr life r, Measures
62 = 22mm. Current cost E35.00 OUR PRICE
only 62
ONLY E13.95 complete with data. 120 o 120
38mm 14'
DC tansi. PANSONIC F13-12C12H 12v DC 5 blade E18.00
PAPST 4124X 24 - 28v DC 5 blade [18.00.
100's of other fens Es Stock.
Call for Details. Post S Packing on all l ans [2 00
1000's of other EX STOCK items including POWER SUPPLIES, RACKS, RELAYS, TRANSFORMERS, TEST
EQUIPMENT, CABLE, CONNECTORS, HARDWARE, MODEMS, TELEPHONES, VARIACS, VDU'S,
PRINTERS. POWER SUPPLIES, OPTICS, KEYBOARDS etc. etc. Give us a call for your spare part
requirements. Stock changes almost daily.
Don't forget, ALL TYPES and QUANTITIES of electronic surplus purchased for CASH
.,
tF
110,

57
APPLICATIONS SUMMARY
LOW-LOSS REGULATED SUPPLY
Voltage drop in conventional
three -terminal regulators is
above 1V. In this circuit, one of
11 described in Siliconix' 'Applications No 1', no voltage drop
occurs provided that input diode
voltage remains above the zener
will be as close to the zener

voltage as the op -amp common mode offset voltage allows.
By selection of the zener
diode, supply current is greater
than 100mA. Output voltage is
adjustable up to the input limit
voltage plus the product of the converter used.
ID X RDSon
The other ten circuits in the
Voltage is doubled by the 7660 eight -page note are a stepper
then regulated by the op -amp motor drive, high -voltage mosfet
and mosfet. For ID of 50mA.
totem -pole, current regulator,
two -channel video switch, j-fet
op -amp input, memory mapped
Vin =Vz(IDXRDSon)
=5.2V+(0.05x 1.2)
interface, simple a -to -d conver=5.26V
ter, bipolar d -to -a converter, a
sampler and
So as long as input voltage does
not drop below 5.26V, output
v
SI7660
or
SI7661
4
VN0300
1k
741
processor -
controlled multiplexer.
EWW300 on reply card
Vout
DISPLAY CONTROLLER
Hardware and software for turn- controller. The microprocessor
ing parallel data into video -form responds to special character
alphanumeric characters are de- codes to give automatic scrollscribed in Motorola note AN851. ing, carriage return, line -feed,
The design includes a micro- paging, screen clearing and curprocessor for display manipula- sor manipulation.
tion and interfacing.
Eight -bit character data,
Main components are a 6808 taken sequentially from screen
microprocessor and a 6845 c.r.t. ram, is turned into 7x9 dot
Address
MC6808
microprocessor
display characters and positioned on the screen by the c.r.t.

controller. Shift -register dot
clocking and sync generation is
also done by the controller.
The circuit and software produce 24 lines of 80 alphanumeric
characters but modifications are
outlined for graphics and semi -
graphics displays. Assembly language software for the screen manipulation functions is given
and described but both hardware
and software for parallel'or serial
interfacing are left to the user.
bus
Dato bus
Frimory bus
/8
Secondary
bus
High speed
timing
~8
MC6845
c
rtc
Address
bus
buffer
18
Dot clock
Character clock
Latch
Row address bu
Horizontal sync
m choract,-
generator
Vertical sync
ft register
Seno( dots
Cursor
splay enable
Cursor
Display enable
Clock
58
'ide.)
+12V
HALL -EFFECT
I.CS
- 115V to
230V
Comprehensive magnetic interfacing and characteristic
Load
Reg.
details for Hall -effect i.cs are

given in Sprague's CN207 applications booklet but there are
also one or two simple output conditioning circuits, such as
this one for s.c.r. driving.
On -state output current from
the Hall -effect switch is low so a
transistor amplifier is used to
step the 9mA output up to 80mA
to turn on the s.c.r.
The 40 -page booklet tells how
the Hall -effect i.cs work and includes sections on rotary activators, ring magnets, current sensors, magnet selection and operating modes.
AUDIO DELAY
40669
1k2
12
SURFACE MOUNTING
Lower manufacturing costs and
smaller board size are the main
benefits of using surface mounted components but there

is also a significant electrical
benefit.
An MF Electronics' note main-
DEVICES
Through holes add

consume space on
board, complicate
design and permit
sided component
Circuits for chorus, vibrato and

reverberation are given in Pana-
sonic's BBD data/application

catalogue for bucket-brigade devices. No circuit details are given
but the catalogue includes full
technical specifications of a
range of delay i.cs that directly
outlining the commercial

advantages of surface-mounting
technology for p.c.b. manufacturers points out that because
duced. Surface -mounted devices

also have shorter legs than conventional ones, which further
reduces these problems.
ly
surface-mounted components
are closer together, propagation
delay and r.f. emission are re-
Absence of through holes simplifies

multi -loyer board design and allows
components on both sides of board
to p.c.b cost
both sides of
multi -layer
only single
mounting
OIL package
Surface mounted
device
replace Mullard types.

The MN3005 is a 4096 -stage
device with 75dB s -to-n ratio for
delays from 20.48 to 205ms. This
100ms reverberation circuit is
accompanied by a p.c.b. foil pattern.
leads curl under package

to increase component density
1'
Bent leads miss holes during

insertion, damage board and
raise pc b defect rate
120k
4----"`/A4
100k
120k
120k
12F2o p
}3
120k
56k
43k
1,I
.r
3n3
100k
56k
MN3005
33s
6
AN6551
3n3
3n3
43
Gndb
Vvv1
220k
20
323
820p
47k
15k
3y3
220k
Echo
MN3 101
Vcc0
control
Ic2
'/t AN6551
1
120k
Gnd
323
b
J
*Adjust
to minimize distortion
59
rUPDATE
Stereo tv in US
wins award
Zenith Electronics Corp. in the
USA has won an Emmy award for
its Multichannel tv sound (MTS)
stereo tv system. The system
allows hi-fi stereo sound to be
broadcast with the tv signal. The
second channel can also be used
to broadcast a simultaneous audio programme which could, for
example be another language for
translations. According to
Zenith, more than 87% of the
continental US population is in
range of a stereo tv signal. More
than 300 stations are equipped
with the MTS system. The federal
Communications Commission
authorized stereo tv broadcasts
in 1964, following the endorsement of the Zenith system by the
Electonic Industries Association.
Euro
information
exchange
Millions of trade documents
could be virtually eliminated by
the adoption of ODETTE (Organisation for data exchange by tele transmission in Europe). The
documents will be replaced with
electronic traffic carrying the
same content but travelling
much faster than post and requiring no manual processing.
Odette was devised by a number of motor manufacturers and
suppliers with the aim of cutting
the cost of paperwork in vehicle
production and of improving bu-
siness methods, to provide instant response to a change, like

the Japanese 'just in time' system. They key to the system is
the Interbridge data standardization package. This translates documents into and back out of
standard formats on the United
Nations' Guidelines for Trade
Data Interchange. The scheme
has just been adopted by the
Society of Motor Manufacturers
and Traders and the systems will
be installed by Systems Designers, of Fleet, Hants.
Some logic array chips are programmed by lasers severing 2m
Electronic bus
data collector
Well actually it's a clipboard co-
vered with barcodes and is being

used by transport authorities
anxious to make their bus services efficient. Survey staff can
interview passengers and use a
portable terminal to record the
answers. Each clipboard has the
relevant details of the bus route
encoded on it. So a simple wipe
of the optical pickup provides
details of the stops, time, purpose of journey, use of travel
cards and the like. When the
terminals are plugged into a
computer, directly or remotely
through a modem, the results
can be transferred immediately
without any human interference. Merseyside passenger
transport executive are to get 32
terminals from GE Electronics
and are planning to survey 1200
routes.
In brief
The 1986/87 series of IEE Faraday Lectures, designed to inform
and educate young people, are to
be presented by ICL who will use
the title "The opportunity of a
lifetime" to promote the idea
that "information and its effective use can be the key to survival
and prosperity of Britain as an
individual nation."
60
links in the metal interconnection circuit. Siemens Production

engineers have developed a grey -shade image processing system
which can distiguish 256 different brightness values, locate the
exact position of a connection point within 30ms and position the
laser with an accuracy of 0.2m. Such a position is indicated by the
middle axis in the picture.
MEETINGSAND
LECTURES
30 October
Clock recovery and synchronization in digital radio. IEE colloquium at IEE, Savoy Place, London WC2. Tel: 01 240 1871 Ext.
269.
31 October
Future printer and plotter technology. IEE colloquium. As

above.
3 November
Millimetre wave component design. IEE colloquium. As above.
System required and system definition. IEE discussion meeting.
14.00h. Further details as above.
4 November
Adaptive man -machine interfaces. IEE colloquium. As above.
3D tv - solid future? IEE lecture
by Dr R Borner. As above.
5 November
High integrity systems - theory
and practice. IEE colloquium. As
above.
6 November
Designing on silicon the challenge for power engineers. IEE
Lecture by D. H. Roberts (GEC).
As above.
Nerve activity measurement
and analysis. IEE/IPSM colloquium. As above.
6 November
Creative digits the impact of
digital technology on tv production. Royal Television Society
1986 Shoenberg Memorial lec-
ture. At the Royal Institution,

Albermarle Street, London W1.
1900h. Details from the Society,
Tel: 01 387 1970.
7 November
The Domesday project - engineering aspects. IEE colloquium. As above.

11 November
Small terminal satellite communications systems. IEE colloquium. As above.
Sub -marine telecommunications. IEE lecture by Dr. T.
Rowbotham (BTRL). As above.
12 November
High definition tv - the technical
challenge. IEE lecture by T.S.
Robson (IBA).
17 November
Giotto - the mission accomplished. IEE lecture by R. Jenkins
(BAe) Electromagnetic Interfe-
rence: practical design and

construction techniques. IEEIE/
IEE symposium. City Conference Centre, Mark Lane, London EC3. Details from IEEIE,
Tel: 01-836 3357 Ext. 212.
[1JPDATE
Wafer
fabrication in
Scotland
In brief
Production has begun in Glenrothes at a new factory for diffused silicon wafers. Sememlab,
who manufacture transistors on
wafers supplied by other manufacturers, have set up the factory
to produce power mos-fet and
bipolar transistors with
3micron geometry. Most of the

products will be used by Sememlab themselves but there will be
enough capacity to supply wafers
to other manufacturers for transistors or mos i.cs compatible
with the processes available.
....and in
France
Construction work has begun in
the South of France of the
construction of a very large factory for the production of inte.
Take -away domestic satellite receivers are to be introduced by

Rediffusion Radio Systems. Two building blocks, RSR-30 receiver
and RKU-10 low noise block, form the basis for both domestic and
commercial systems. 1.2, 1.5, and 1.7m dishes are available and a
basic home installation is expected to retail at under 1000.
grated circuits using direct

electron-beam lithography to gives considerably more fanout.
In order to take full advantage of
provide rapid turnaround for the
these
advancements, it was
devices.
European Silicon Structure necessary to rearrange the power

and signal pins. These will help
(ES2) is a result of collaboration
between several leading systems to reduce noise and overcome
manufacturers in Europe inclu- the effects of simultaneous
ding Philips, Brown Boveri, switching within the devices.
Other changes will reduce the
Saab, Bull, Olivetti, British Aeself inductance encountered
rospace and Telefonica.
with some i.cs. The principal
The factory is specifically designed to produce application- changes will be that the supply
voltage and ground pins will be
specific i.cs which would be too
in the middle of d.i.l. Package
specialized for the large manuinstead
of the ends. Inputs will
facturers to tackle with their
surround
the supply voltage pins
conventional production and outputs
will be near the
methods. Design stages will be
developed on a silicon compiler, ground pins with control signals
a software system that reduces at the ends.
design time dramatically.
The shell of the building is to
be complete and equipment installed next spring; the first products to emerge in summer.
Acorn Computers achieved an
operating profit of 298k in the
first half of 1986, compared with
a loss in the previous six months
of 97k and the disastrous 10m
The joint development of adv- loss at the beginning of 1985.
anced c-mos (a.c.1) by Philip/ The turnaround has been achieSignetics and Texas aims to proved despite the expense of launduce the speed of advanced bi- ching new products and maintaipolar logic with the low current ning the same level of r & d
consumption of c-mos. The a.c.l. expenditure. Brian Long, Acorn
devices will be three times as fast managing director puts the sucas existing high-speed c-mos cess of the Master series at the
logic i.cs while offering 24mA of top of his list to explain the
output drive current, which recovery. There was also the sale
Acorn back in
the black
New pinouts for
new logic
of a licence to VLSI Technology

the produce the Acorn RISC
chip; the successful expansion
into specialist markets, such as
health care and doctors' records,
and o.e.m. sales to major customer for inclusion in their own
products. Long also points out
the loyalty of customers who can
continue to exploit their existing
investments by getting the latest

upgrades. Acorn's commitment
to continuity has played a cruicial role in users' loyalty, he said.
How safe are

VDUs?
There have been allegations of
adverse effects of working with
computer screens for pregnant
women. The second international meeting to examine the allegations of reproductive hazards
from v.d.u.s is to take place at the
Cumberland Hotel, London on
25th and 26th November. Speakers, mostly medical experts
from Scandinavia, North America and Europe, will present the
results of their studies. The meeting is organized by Humane
Technology, a consultancy specializing in the human aspects of
computer systems. Further details from HT, Telephone: Nottingham (0602) 475563
Finland is to become an associate

member of the European Space
Agency. It will participate in the
science programme and in the
Earth observation preparatory
programme. This latter is a fiveyear programme to prepare Europe's activities for a further ten
years.
The International Train, British Rail Engineering's attempt
to sell new rolling stock abroad,
has lots of electronics on board.
There is a cellular payphone linked to Cellnet. A prototype seat
reservation system transmits details t the train before_departure. This and other information
can be displayed to the passengers, individually or collectively.
The screens can also be used to
show films and tv programs.
British Telecom has provided all
this and is also proud of its
control and monitoring systems,
developed specifically for railway
applications.
CONFERENCES &
LECTURES
4-7 November 1986
Radio relay systems. European
conference in Munich. Details
from Dr P. Guls, ANT Nachrich-
tentechnik GmbH, Gerberstrasse 33, D-7150 Backnang,

FRGermany.
13-15 November 1986
The history of television. IEE and
others. International conference
at IEE, Savoy Place, London
WC2. Tel: 01 240 1871 Ext. 222.
18-22 November 1986
Computers in the city. Conference and Exhibition. Barbican
Centre, London. Online, Telephone 01 868 4466.
22-23 November 1986
Hands-on show Music recording
exhibition, with seminars.
Strand Palace Hotel, The Strand,

London WC2. Organized by Turnkey, Telephone 01-202 4366.
2-3 December 1986
Satellite Communications.
Conference. Tara Hotel, London
Online, Tel: 01 868 4466.
2-5 December 1986
Technospace International space
industries and technologies ex-
hibition. Bordeaux -Congres,
Bordeaux, France. Details: Technospace, 12 Place de la Bourse,

33076 Bordeaux Cedex, France.
61
PDATE
Still in the
picture
CONFERENCE
& EXHIBITIONS
3-4 December 1986
Satellite Broadcasting. Confer-
Television South has acquired

two systems for the storage of
still pictures on optical discs.
The pictures are stored in EBU/
SMPTE format and a com-
ence. Tara Hotel, London

Online, as above.
9-11 December 1986

Videotex International Conference and exhibition. Wembley
plimentary database system

keeps a comprehensive record of
the contents of each disc. Each
optical disc can store over 1000
full-sized broadcast quality pictures. An add-on option is Picture File which allows the stills
to be viewed in full frame or it is
possible to get 30 pictures onto
one screen for comparison.

Other options include video
manipulation of the pictures so
that they can, for example, be
flipped, changed in size, be cropped or repositioned: Art File provides a video "painting" system.
The Gallery 2000 system is produced and supplied by Logica.
DTI look into

parts of the
spectrum
The Department of Trade and
Industry has commissioned a
short-term study on spectrum
planning for fixed terrestrial
radio services in the unexploited
frequency range of 30 to 60GHz.
The study will review the future
of existing and potential microwave fixed links. It will pay particular attention to the competitive position of UK equipment
manufacturers and the likely developments in technology over
the next five years.
Outline planning for this band
has been completed but the DTI
would welcome contact with

those with an interest in this
frequency range. Comment

should go to the consultant, Graham Taylor, Ewbank Preece
Consulting Ltd, Prudential
House, North Street, Brighton
BN1 IRE.
Meanwhile, in another part of

the spectrum, more frequencies
are to be made available for cellular telephones in central London. The frequencies immediately below those presently used for
cellular radio are allocated to the
MoD. They have agreed that,
subject to certain restrictions,
these frequencies may be used by
cellular radio operators in Lon-
62
Conference Centre, London.

Online, as above.
23-27 February 1987

Fiarex 87 international electronics trade fair. Rai Exhibition
Centre, Amsterdam. Rai
Crest awards for young people

At work on his Swamp Rat air
boat is 18 -year -old Christopher
Cox, who designed it as a pilot
project for the Crest Award

scheme. Crest stands for Creativity in Science and Technology;
and the aim of the scheme is to
do for young people's scientific
and technical awareness what
the Duke of Edinburgh's award
has done for overall personal
development.
Launched by the British Association for the Advancement of
Science at its 1986 meeting in
Bristol, Crest offers awards at
gold, silver or bronze level for
knowledge, problem -solving

ability and perseverance.
Young people aged 11 to 18
can take part either as individuals or as teams. And their entries
may consist of straightforward'
scientific investigations or design and construction studies.
don. Initially a further 200 channels will become available to

each operator - compared with
the current 300. If the demand
justifies it, a further 120 channel
each could become available.
The MoD restriction is that the
area of operation should be limited to a 6-mile radius around
Charing Cross.
Yet more news from the DTI is
that they have published a consultative document on the possibility of establishing an independent third -party quality assurance scheme within the radio
communication industry. This
in effect could lead to a self
regulating radio frequency spectrum, devolved from the RRD.
The scheme could also reduce
the number of international
Prospective gold award winners are to be encouraged to

form links with industry and
higher education for help and
advice. The scheme will undoubtedly give job -hunting
school leavers a useful record of
achievement to supplement
their examination results. But
the organizers hope it will encourage scientific and technological activity among all
secondary school pupils and in
doing help to reduce Britain's
present shortage of skilled engineers.
Financial backing for Crest
has come from Philips Electronics, BP, the Wellcome Foundation and the Department of
Education.
For more details, write to
Crest at the British Association,
Fortress House, 23 Savile Row,
London W1X lAB.
Gebouw, Europaplein, Amsterdam.

3-6 March 1987
International Open Systems

Conference (and a MAP seminar,
4 March). Barbican Centre, London. Online, as above Semicon
Europa 87 exhibition of semiconductor equipment and materials. Zuspa Convention Centre,
Zurich. Enquiries to Cochrane
Communications, Tel: 01 353
8807.
24-26 March 1987

Cadcam 87 exhibition. NEC
Birmingham.
EMAP int. Exhibitions, Tel: 01
608 1161.
25-26 March 1987

Instrumentation Bristol 87 Exhibition. Bristol Crest Hotel. Trident Int. Exhibitions, Tel: 0822
4671.
6-8 April 1987
Offshore computers conference
and exhibition. Heathrow Penta
Hotel, London. Offshore Conferences, Tel: 01 549 5831.
assessments needed for type approval. Manufacturers who are

certified to certain levels of product conformity will produce 28-29 April 1987
better goods. If the responsibility Cellular and mobile communicafor type approval is put directly tions Conference. Barbican Cenon the manufacturers and im- tre, London. Online, as above.
porters, the loophole, that allows Value-added network services
illegal good to be sold legally (VANS) Conference. Barbican
would be closed. Copies of the Centre, London. Online as
document, full title of which is above.
"Proposal for the establishment
within the radio communica- 28-30 April 1987
tions industry of an independent City 'communications exhibithird party quality assurance tion. Barbican Centre, London.
scheme under the aegis of the Online, As above.
National Accreditation Council
for Certification Bodies" are
obtainable from the DTI, Room
409, Waterloo Bridge House,
Waterloo Road, London SEI
8UA.
18-20 June 1987

Television measurements, Third
international IERE conference.
Montreux, Switzerland. IERE
Tel: 01 388 3071.
Broadcast radio -data

As the BBC and IBA prepare RDS services for next
year's start, this review describes radio -data on both
v.h.f. and 1.f.
D.T. WRIGHT AND S.M. EDWARDSON

For more than a decade, broadcasters
have been adding auxiliary data signals

to their normal radio and television
transmissions in such a way that they go
unnoticed by viewers and listeners not
equipped to receive them. Probably the first
application of this kind, which barely warrants recognition as a one -bit data signal,
was the addition in the early 1960s of a
23kHz tone to BBC monophonic v.h.f./f.m.
radio broadcasts to control the powering of
unattended relay transmitters.
For some years after that, attention in the
BBC was focused on television. Insertion
Communication Equipment (ICE) was an
in-house system designed in the early 1970s
to add data signals to an unused line in each
field blanking interval for such applications
as the control of opt -out switching at regional centres, the synchronization of television
waveform generators at remot sources, and
to provide low -speed teleprinter channels.
Teletext, a public information service
which came into use in 1974, made much
more ambitious use of the field blanking
interval by cramming into each line 40
useful bytes of information, corresponding
to one row of characters. Using two data
lines per field and 24 rows per page, this
allowed a magazine of 100 pages of text to be
transmitted in a cycle lasting no longer than
25 seconds. Teletext facilities were included
in 20% of television receivers sold or rented
in the UK during 1985 and use of the system
is widespread abroad. It has been extended to
provide for the transmission of computer
programs (telesoftware) and, by means of
Datacast, for the delivery of specialised
information to closed user -groups.
Meanwhile, the possibility of using radio
broadcasts also as a means of conveying
extra digital information was being investigated.
Around 1978, work was started on a
means of adding data signals to v.h.f. radio
transmissions. It soon became evident that
an additional data-modulated subcarrier
offered the best promise. The main aim was
to assist in the operation of v.h.f. receivers by
providing identification of the transmitter
and the programme service; but other uses
were envisaged, such as the conveying of
brief messages which would appear on a
display built into the receiver.
International discussions resulted in an
EBU Radio Data System (RDS) specifications
which has also become a draft CCIR recom-
mendation.
The BBC intends to operate a regular RDS
service from late 1987. Sweden began a
service earlier this year and the Federal
Republic of Germany plans to start in the
spring of 1988.
This development prompted the search

for a companion service for use on l.f. and
m.f. radio, but it was eventually realized that
it would be both more convenient and
cheaper to include information relating to
I.f. and m.f. broadcasts in the v.h.f. data
signals. However, by this time a data channel
for l.f. and m.f. had been devised which,
though of limited capacity, could have a
number of useful applications particularly to
closed user -groups. The UK electricity supply industry uses l.f. radio -data regularly for
various uses in its Radio Teleswitching electricity load management system. Other uses
are foreseen.
RDS ON V.H.F.
In the v.h.f. radio -data system2, a subcarrier
at 57kHz is added at low level to deviate the
main carrier by approximately 2kHz. The
data signal modulates this carrier using
double-sideband suppressed-carrier modulation. The overall bit rate of the data
stream is 1187.5 bit/s (1187.5=57000/48)
which, with biphase encoding and the specified data-shaping filtering, gives an overall
bandwidth after modulation of 4.8kHz.
The data is structured in 104 -bit groups,
each comprising four 26 -bit blocks. Each
block contains 16 message bits' and 10
protection bits. Two kinds of message are
..
*
m;,
carried by the data blocks - short ones

repeated rapidly for automatic tuning and
longer ones repeated less often for display to
the user.
OTHER SYSTEMS
number of specialist information systems

are in operation in the USA. For example, a
service called Telerate provides a data channel using the SCA subcarrier at 67kHz
frequency -modulated by data at 4800baud. If
this system were used in Europe, its higher
bit -rate might prove incompatible with
many older receivers. Moreover, because of
the high spectral density of v.h.f./f.m. transmissions in some parts of Europe, the
question of adjacent -channel interference
would need careful study.
A
RADIO-DATA ON L.F.
At about the same time as work on l.f. and
m.f. radio data systems was beginning to

succeed, the UK electricity supply industry
(ESI) approached the BBC expressing interest in a low bit -rate data channel with
national (l.f.) coverage.
The requirements for radio -data on I.f.
and m.f. called for the same balance between
compatibility (existing reception not impaired) and adequate ruggedness of the data
signal. In addition, for l.f. operation there
e,,,weemeremeneen,,:meatemeasemag
maw
BBC plans for RDS

intends to provide RDS radio data signals on all v.h.f. transmissions
in England by September 1987. The
initial service will include
quency would be a better signal having the

same PI code. This code is not intended for
direct display.
programme identification
programme service name
alternative frequencies
frequencies for other networks
clock time and date
These data items are the simplest to provide
at the programme source, yet at the same time
are those which give the greatest help with
receiver tuning, both automatic and manual.
In this way, the initial service represents the
most economic way of encouraging the development of advanced receivers which make
use of the new signals.
PS codes provide text of up to eight characters

for display on the receiver to tell the listener
what programme is being broadcast by the
station to which it is tuned. An example of a
name could be "BBC R4". The length of this
name is restricted to keep down the cost of the
receiver. The programme service code is not
intended to be used for automatic tuning.
The BBC
--CTPI
PS
AF
ON
PI codes enable the receiver to distinguish

between countries and areas in which the
same programme is transmitted, and identify
the programme itself. The code is assigned to
each individual programme, to distinguish it
from all other programmes. One application of
this information would be to enable the
receiver to search automatically for an
alternative frequency in case of bad reception:
the criterion of change -over to the new fre-
AF codes list the frequencies of transmitters

broadcasting the same programme in adjacent
reception areas. Receivers equipped with

memory can store the list and use it when
switching to an another transmitter, as a
faster alternative to searching. Up to 25 frequencies can be transmitted. This facility is
particularly useful in the case of car and
portable radios.
ON codes can provide up to 25 alternative
frequencies for each of up to eight other
networks. The relation to the corresponding
programme is established by means of the
relevant PI code.
63
any of the other 29 time -slots in each
minute.
;lnput
RADIO TELESWITCHING
doto sequence
Although this system is

application rather than
11
a-225
Biphose
coded doto sequence
Fig.1. Radio -data modulation of an I.f. carrier as a function of time. Above is the input
sequence; below, the same sequence

biphase-coded.
Time code
block
Minute
edge
Fig2. Arrangement of data blocks on the

BBC's 200kHz I.f. service. Block 0 begins
exactly on the clock -time minute.
was the special problem of the use of a
synchronized group of transmitters whose
carrier frequency was used as a standard.
Accordingly, the basic phase -modulation
parameters already shown to be suitable for
use on m.f. and l.f. were further developed
specifically for use on the BBC's 200kHz
Radio 4 UK 1.f. network3, which uses only
three transmitters to cover the whole of the

British Isles. This development as carried
out under a collaborative agreement between the BBC and the ESI.
Because the 200kHz transmissions are
used as a frequency standard, the data was
biphase-encoded to ensure that there would
be no d.c. component in the phase modulation (Fig.1). The symbol rate was
50baud and the data rate 25 bit/s.
The data is divided into 50 -bit blocks each
lasting two seconds. Of the 50 bits, one is a
synchronizing prefix, thirteen are used for a
c.r.c. check (which also plays a part in the
synchronizing process) and four are in effect
a packet address, identifying the block as
belonging to one of 16 data channels. The
remaining 32 bits in each block yield an
overall useful bit rate for addressed data
channels of 16 bit/s.
Since each block takes exactly two
seconds to transmit, there are 30 blocks per
minute; and the block boundaries are phased
so that one of them occurs exactly on the
clock-time minute (Fig.2). The block immediately before the minute carries a data
and time code and is identified as channel 0.
The remaining 15 channel numbers, or
packet addresses, can be used arbitrarily in
64
a closed user -group

a
broadcast service,
is described here because many of its

techniques are likely to be relevant to other
it
broadcast applications.
The ESI's interest in the data channel is
primarily for the remote control of electronic time -switches. These switches, which
are known as radio teleswitch receivers, are
expected to become increasingly costeffective replacements for the mechanical
time -switch driven by a synchronous motor
with a clockwork (spring) reserve. The electronic time -switch possesses the great
advantage of automatic time resetting,
which is especially valuable during changes
between winter and summer time. Moreover, after a mains failure, the clock is reset
automatically from the time code.
In addition to their use of the time clock,
the ESI have contracted with the BBC for the
use of up to five of the remaining 29 data
blocks in each minute. Each such block can
be used to set a group of radio teleswitches
with new on and off times. This service has
been running with duplicated transmission
equipment since 1 April, 1985.
Given such monitoring, the transmitted

clock time could be guaranteed accurate to
within 5ms at any point in the UK. At present
the absolute accuracy is 0.5s (but the error
value is very stable!).
SIMILAR SYSTEMS
For many years a system developed by the
Barry Research Corporation of Palo Alto,
California, has used phase modulation to
carry teleprinter signals on h.f. broadcasts.
Certain local electricity supply authorities in
the United States use a nearby m.f. transmitter to carry control data connected with
electricity metering5 and, in East Germany,
RFZ at Dresden use a transmitter to carry
asynchronous data at up to 100bit/s6. This
four-fold increase over the BBC system is
possible because the transmission is not a
frequency standard and hence there is no
need to use biphase encoding; and because
there is no insistence on avoiding disturbance to existing receivers under worst -case
mush area conditions.
WEATHER INFORMATION
Several other uses for the remaining unused
capacity of the I.f. radio -data channel have
been considered but none has yet been
implemented.
The most likely use is for coded weather
forecast information for sea or land areas.
TRANSMISSION CHAIN
Such a service conveyed by a data channel
Where two or more transmitters carrying would make possible an automatic gale the same modulation share a common car- warning alert for boat owners who might not
rier frequency there are areas of of mutual be listening to the radio when the spoken
interference, known as mush areas, between warning was given. It would be possible to
the transmitters where the field strengths code a complex gale warning for a single sea
are almost equal. The mutual interference area in no more than two data blocks (64
can give rise to severe distortion and a loss of bits) which could be transmitted in only 47.
A possibility which makes slightly less
service area, particularly where near cancellation occurs. Timings of the modula- efficient use of the data channel but offers
tions from the transmitters involved are a the prospect of completely automatic operavery important consideration and ideally tion is dictionary encoding of already should be coincident at all frequencies. This existing forecast texts. A five-minute forecondition is difficult to achieve in practice, cast could be retransmitted in dictionary particularly at high audio frequencies which encoded form at least once per hour.
demand a timing accuracy of about 30s, This paper was presented at IBC, Brighton in
but a useful improvement is nevertheless September
obtainable'.
References
A similar requirement applies to timings
1. Specifications of the radio -data system RDS for
of the data signal modulations. Both data VHF/FM sound broadcasting, European Broadany
differmatch:
content and timings must
casting Union, 1984. EBU technical publication
ence in the phase modulations can give rise
3244-E.
to phase -to-amplitude -modulation (p.m.-to- 2. D. Kopitz, Development of Radio-data transa.m.) conversion, which can be heard on a missions from the European point of view, IBC 82,
normal a.m. receiver. Fortunately, because IEE conference publication No.220, 273-275.
the data waveform contains only low fre- 3. D.T. Wright, LF Radio -data: specification of
BBC phase -modulated transmissions on longquencies, timing requirements are much
Research Department Report no.1984/
less stringent than for the audio signals. The wave. BBC
19.
required tolerance in data signal modulation
4. D.J. Whythe, Reduction of mush -area distorbetween any two transmitters is lms.
tion in common -frequency m.f. transmitter netProvided this is achieved, interference from works. The Radio and Electronic Engineer, vol. 44
the data signal is found to remain inaudible no.8, August 1984.
even in the worst nulls of the mush areas
5. L. Martinez, Narrow band paging or control
where the programme may be severely dis- radio system, 1980. United States Patent no.4 208
torted. Recovery of the data itself if substan- 630.
tially unaffected by modulation timing 6. F. List, A system for the transmission of
supplementary information in amplitude errors less than about 5ms.
The clock frequency of the source data is
locked to a rubidium reference and so the
transmitted time code is suitable for use as a
time standard provided that the means are
available to monitor its continued accuracy.
modulation sound broadcasting. Proceedings of

the 14 Verkehrswissenschaftliche Tage, 10-13
September, 1984, ppV/7-V/10.
7. C.P. Sandbank, D.T. Wright and R.P. Rogers,
Broadcast information transmission. UK Patent
GB 2087468B.
Programmable logic
design
This decoder for 68020 dynamic bus sizing is an example
of how one programmable logic device can replace a
number of standard logic i.cs.
CHRIS JAY
The M68020 is the first full 32 bit
implementation of the 68000 microprocessor family. It has a 32 bit address

bus and 32 -bit -wide data path. Data -bus
transfers of 32 -bit long word, 16 -bit and byte
width, Fig.1, are possible using the processor's dynamic bus sizing capability.
When the 68020 writes data it drives all 32
data lines and when reading data it assumes
that the port, whether memory or peripheral, is 32 bits wide. The processor receives
acknowledgement of the size of the port
through two data-size acknowledge inputs,
DSACKo and DSACKI. These signals correspond
to the DSCAK input of the 68000 microprocessor, Table 1.
The one-of -four binary code at the DSACK
inputs indicates whether the port currently
being accessed is byte, word or long -word
width, or whether wait states should be
inserted.
During each bus cycle the port size is

indicated to the microprocessor via the DSACK
inputs, so the processor can dynamically
determine the port size during bus accesses.
During execution, optimum performance
is achieved when all operands are aligned.
Misaligned operands can cause additional
bus cycles which degrade overall execution
Operands may be accessed on any byte

boundary but op -code alignment is restricted to even -byte boundaries for execution efficiency. Aligned -word operands commence on even -byte boundaries and aligned
long words reside on even word boundaries.
Any misplaced operands from a base address
are considered misaligned.
TABLE 1.
DSACK
Insert wait states in current bus cycle

Complete cycle- data -bus port 8 bits
Complete cycle data -bus port 16 bits
Complete cycle data -bus port 32 bits
o
0
A,
Offset bytes
+o
+1
+2
+3
TABLE 3. SIZE output encodings.
slzl
sizo
Size
Byte
Word
3 byte
Long -word
0133
31
operand
0P2
OP3
15
Byte operand
OP3
0
Fig.1. Internal operand representation.

During a processor read cycle the 68020 Data -bus width of the 68020 can be adlatches the logic states of all 32 data-bus bits, justed dynamically.
initially assuming that the port is 32 -bits
wide. If the data -size acknowledge input
MC 68020
reports that the port is long word, operation
OP1
OP2
OP3
OPO
continues with the next cycle.
3
2
Internal
If the port is 16 -bits wide, two read cycles source/dest.
are produced, the first word followed by the
second. A byte -wide port is read over four Multiplexer
Routing and duplication
separate cycles. Data bus allocation for long
word is on data lines 31 to zero, for word
transfers 31 to 16, and for byte transfers over External
031-024 023-016 0154
07.00
data bus
Multiplexing for routing or duplicating

any operand bytes is shown in Fig.2. Normal
aligned placement for opo would be D31-24,
but in a misaligned transfer opo could be
routed to any other byte boundary.
Addressing can be considered to be longword addressing through address lines AL_31
with A01 providing a four -byte location offset
from the long -word base address, Table 2.
Address
Long words are subdivided into four bytes on

the data bus, op,,.,. Normal data routing
assigns opo to data lines D31_24, oPi to 023-16,
oP2 to D15.8 and op3 to D7_o. This would be the
case for aligned data transfer.
To allow misaligned transfer, data bytes
020.3 may be routed to any byte section in the
32 -bit wide data bus. The microprocessor's
size outputs S1z0,1 and address outputs A0,1
can be decoded to route data bytes to their
appropriate positions on the data bus. Table
3 shows the SIZE output encodings for longword, three-byte, word and byte transfers.
The encoded state on siz0.1 indicates how
many bytes are to be transferred on the next
bus cycle. Numerical encoding of the SIZE
outputs will be equal to or greater than the
number of bytes to be transferred. For
example if a long -word port is read and a
transfer to a word -wide port is executed,
n+0
Byte
Byte
IByte
Byte
32 -bit
Address
Address
n+0 Byte
n+2 Byte
0
2
Byte
Byte
n+0 Byte
Byte
n+2 Byte
n+ 3 Byte
n+1
DATA ROUTING
codes and results.
TABLE 2. Address offset encodings

A,
Word
0P2
OP1
OPO
operand
efficiency.
31 to 24.
DYNAMIC BUS SIZING
Long -word
16
port
-bit port
-bit port
2
3
68020 interface to various port

sizes. When a byte -wide port size is
selected, bytes pass sequentially.
Fig.2.
Long -word operand

OP() I OP1
10P2I OP3I
0
31
Dato bus
031
016
Word memory
m s h
l s.b.
Memory control
MC68020
SIZ1 SIZO A l A
DSACK
DSACKO
OPO
OP1
0P2
OP3
Fig.3. Example of long-word
transfer to
word bus with control -signal states.
65
outputs will indicate a four byte transfer, but only two bytes will be moved.
An example of this is the transfer of data
from a long-word port to a word port, which
occurs over two cycles with the most significant word first. Initially, and while
slzo,l
transferring the most -significant word, the

SIZE outputs indicate a long -word transfer
and indicate a word transfer when the
remaining least -significant word is transferred, Fig.3.
Figure 4 shows the condition of the SIZE
outputs and states of 4,1 in a long-word
transfer to an eight-bit port. Table 4 shows
conditions required for an internal -to external data-bus multiplexer. If an aligned
long -word to byte transfer is performed the
long word is latched into the data inputs.
Writing to a byte port is performed in four
cycles. Firstly state 1 in Table 4 is performed;
SIz1,0 and A1,0 are all low as OP0 is written to
1)3124. Next, state 2 indicates three more
bytes to be transferred at an address offset of
one, i.e. 1101 on slzl,0 and A1,0 outputs.
Operand oP1 is placed on lines D31-24.
In the third cycle, state 3, s121,o and A1,0
contain 10x0 respectively and ope is placed
on data lines D31_24. In the final cycle, op3 is
sent to data lines D31-24, with slzl,tl and A1,0 in
the logic condition of Olxx, as in Table 4,
TABLE 4. 68020 internal -to -external data -bus multiplexer
Source/destination,
external data -bus connection
Address
Size
Transfer size slzl
seZO
Al
Ao
D3124
D23-16
015.8
07.0
Byte
OP3
OP3
OP3
OP3
OP2
OP3
OP2
OP3
OP2
OP2
OP3
OP2
OPI
OP2
OP3
OPj
OPI
OPI
OP2
OP3
OPI
OP2
OPI
OP2
OPI
OPI
OPI.
OPI
OP0
OPI
OP2
OP3
OP0
OPO
OPI
OP2
OPO
OPI
OPO
OPI
OP0
OP0
OPI.
OP0
Word
State 4
State 3
3 byte
State 2
Long word
State 1
'0n write cycles this byte is output, ignored
on read cycles
x = don't care
OP labels on the external data bus refer to a partiuclar byte of the operand
that will be read or written on that section of the data bus.
state 4.
TABLE 5. Data -bus activity for byte, word and long -word ports.
MISALIGNED TRANSFERS
Misaligned data can occur for word or
long -word operands. Examples of misaligned tranfers are words transferred to
odd -address boundaries and long words
transferred outside the four -byte boundary
of a long word.
Figure 5 shows a long -word transfer to a
word -wide port, the DSACK outputs indicating
a word -wide port. Three cycles are required.
The word boundary is even but opo must be
routed to an odd byte boundary, to the l.s.b.
Contents of the m.s.b. must remain un -
Transfer size
Byte
Word
Three -byte
operand
Long-word
OP3
OR
Long -word
31
Data bus
Note,
srz1
SIZo
Al
Ao
Data -bus active sections

03124
D23-16
B,W.L
W, L
B.W
B.W.L
0
0
W,L
W,L
B. W
B.W.L
0
0
W,L
W,L
B. W
B.W,L
o
0
0
0
0
0
1
1
are byte, W are word and
D15-8
07.0
W
W
W,L
W,L
B.W
are long -word ports.
D24
D31
MC 68020
Byte memory
Memory control
SIZ1 SIZO A7
AO DSACK
OPO
OP;
0P2
OP3
DSACK
Fig.4. Example of long -word transfer to

byte bus.
Long -word operand
TABLE 6. Fuse -plot output from the PALASM assembler for the PAL12L6 bus -size decoder, see Fig.8.
11
0123
-X-
16
-X-
OPO
31
OP1
OP2
016
Word memory
m.s.b
Lsb.
xxx
OPO
OP;
OP2
OP3
xxx
MC
SIZ
68020
SIZ
Memor
A2 At AO DSACK1
control
-X X-X-X
-X- X-
50
51
Fig.5. Misaligned long -word transfer to

word bus example.
-XX-
1111
1111
2345
6789
2222
4567
---
2233
8901
AO'A1
SIZO'/SIZIYA1
/A1'/AO'SIZ1'/SIZO
Al
Al
X
-X
SIZO'/SIZ1'iA0
-X
SIZO'/SIZ1'iA0
-X-
-X
X-
-X
X-
= fuse not blown (L,N,O), - - fuse blown (H.P,1)

Number of fuses blown = 384
X
2222
0123
AO
48
49
DSACKO
-X-
-X-
D31
-X-X
40
24
25
Data bus
-X
X-
32
OP3I
XX-X
-X
17
I
8901
-X-
8
9
10
4567
--
AO
SIZO'/A0/S121
SIZ1'/AO'/A1
SIZO'/A1'/SIZ1
AO'/A1'S1Z1'/SIZO
LIST 1. Bus -sizing logic design specifications from the

PALASM assembler.
UUD
CHIP DECODE PAL12L6

AO Al SIZO SIZ1 NC NC NC NC NC GND
NC NC LLD UD LD UMD UUD LMD NC VCC
EQUATIONS
/UUD = AO + Al
/UMD = Al + SIZO'/SIZ1'/A0
/LMD = AO'A1 + SIZO'/SIZ1'/A1 + /A1'/AO'SIZ1'/SIZO
/LLD = SIZO'/AO'/SIZ1 + SIZI'/A0'/A1
+ SIZO'/A1'/SIZ1 + AO'/A1'SIZ1'SIZO
UMD
/UD = AO
/LD = SIZO'/SIZ1'/A0
SIMULATION
TRACE-ON AO AI SIZO SIZ1 UUD UMD LMD LLD UD LD
SETF /A0/A1 SIZO/SIZ1
SETF AO/A1 SIZO/SIZ1
SETF /AO Al SIZO/SIZ1
SETF AO Al SIZO/SIZ1
SETF /AO/Al/SIZO SIZ1
SETFAO/Al/SIZO SIZ1
SETF /AO Al/SIZO SIZ1
SETF AO Al/SIZO SIZ1
SETF /A0/A1 SIZO SIZ1
SETF AO/A1 SIZO SIZ1
SETF /AO Al SIZO SIZ1
SETF AO Al SIZO SIZ1
SETF /A0/Al/SIZO/SIZ1
LMD
SETFAO/Al/SIZO/SIZ1
SETF /AO Al/SIZO/SIZI
SETF AO Al/SIZO/SIZ1
TRACE -OFF AO Al SIZO SIZ1 UUD UMD LMD LLD UD LD
Note: In PALASM, oblique replaces the negating bar

and the asterisk replaces the multiplication sign.
changed during the data transfer. Lines sizo,l

indicate a long-word transfer.
The next cycle transfers op1,2 with sum
indicating a three -byte transfer. The final
cycle indicates the transfer of op3 to the
m.s.b. with the contents of the l.s.b. remaining unchanged. Outputs sizo,1 indicate that a
single byte is being transferred,
Aligned and non-aligned transfers are
further detailed in the 68020 user's manual.
DATA-SELECT GENERATOR
Hardware for decoding size and address

information, Fig.6, must comply with the
requirements of the data -bus activity shown
in Table 5.
The decoder can be constructed from a
number of And and Or gates designed to
decode the 68020 address and slzE outputs or
alternatively the logic may be condensed
into programmable -array logic (pal) -which
reduces the number of packages required
from about six 14-pin packs to one 20 -pin
d.i.l. pack. Reliability is also improved due to
fewer packages and interconnections.
This implementation, Fig.6, consists four
true and complement inputs, derived from
68020 lines Ao and sizo,1, feeding an array of
internconnections. These drive a sum of
products configuration.
Decoded outputs UUD, UMD, LMD, and LLD ar.
used for accessing 32 bit ports and are
designated upper -upper data, upper -middle
data, lower -middle data and lower -lower
data. Upper and lower-data lines UD and LD are
used in accessing 16 -bit wide ports. The
relationship of these signals is shown in
1
Table 5.
PAL CONSIDERATIONS
other
combinational function, digital designers
To select a pal to perform this or any
LLD
UD
LD
Ao
A1
UUD
Upper upper data (32 -bit
UMD
Upper middle dota
LMD
Lower middle data
LLD
Lower lower data
UD
Upper
L D
Lower
SIZO
SIZ
dato
(16
port)
-bit port
dato
11
Fig.6. Byte data -select logic for 16 and 32 -bit ports.
need to make two initial observations about

the logic circuitry.
First the number of inputs and outputs to
and from the circuit should be fewer than or
equal to the number of inputs and outputs of
the pal itself. This constraint is imposed by
the number of pins on the d.i.l. package.
Secondly the number of product terms or
And gates available in the pal device and,
equally important, their distribution to the
summation or Or gates must be considered.
Figure 7 is a simplified view of a pal device.
Inputs are connected to true/complement
buffers, outputs of which drive a large fuse
array. In bipolar devices, the array consists
of titanium -tungsten fuses whereas in c-mos
types, floating gates are used.
The fuse array connects to And gates or
`product terms', each column representing a
discrete input to the product term. Output of
the product term drives
non -
programmable interconnecting array connected to 'sum terms' (Or gates) which drive
the output pins through buffers. Using a pal
programmer, the logic designer removes all
unwanted fuses in the array.
The byte data -select generator for 16 and
32 -bit ports shown in Fig.6 is an ideal circuit
for encoding into pal. One potentially suitable device is the PAL12H6. There are 12
inputs to the 12H6, only four of which would
be needed for microprocessor outputs Aa,1
and slzp,l. All six outputs of the 12H6 would
be needed for decoded outputs signals WD.
UMD, LMD, LLD, UD and LD.
Signals LLD and LMD require four product
terms each and UMD and LD both require three
product terms. Of the six outputs, two are
the summation of four product terms and
four are the summation of two product
67
I,
12
13
Io
'OR'array
IW W?
I--
(fixed)
Fig.9. States of the dynamic bus sizing

logic generated using the PALASM2 pal
assembler.
XX
r.
XX
XXX
XXX XXX
x
XXXX
J
J
SIZo
J
) )
SIZ,
UMU
)
J
input
UUD
)
) )
XX
x
r-Ao
LMD
LLD
r
UD
AND gates
array
(programmable)
'AND'
LO
output generated from test

vectors.
Test vectors ore derived from the PAL
design specification by running the
simulate option in PALASM2
VTRACE
Fig.7. Simplified programmable array logic. The And gates are referred to as product
terms and the Or gates as sum terms. Equivalent logic for the true/complement buffers
driving the fuse array is shown separately.
terms each. This means that the product

term allocation of the 12H6 is unsuitable for
this application.
Using Karnaugh-map manipulation to reduce the number of product terms though, a
12H6 device with active low outputs the
12L6 - is suitable, Fig.8.
COMPUTERDESIGN
Fuse plots of earlier pals can be assembled
using a program written in Fortran called

PALASMI. A more advanced assembler written in Pascal for both newer and older
devices
PALASM2
is currently under
development. This new software runs on
IBM p.cs under PC -DOS, or VAX under the
VMS operating system.
From the original design specification
shown in List 1, PALASM2 automatically
converts the Boolean statements into a fuse
plot as shown in Table 6. Positions marked x
on the fuse plot remain intact and positions
marked are programmed. Numbering at
the fuse -array column heads relates to individual inputs to each product term. In the
12L6 there are 32 inputs to each product
term. Row numbering on the left-hand side
of the fuse array indicates the individual
product terms. Here, only product terms
with programmed fuse inputs are shown.
Although there are only 16 product terms in
a 12L6, the numbering system assigned to
the array is general for a range of pal devices
68
with a varied distribution of product term

input and product term distribution.
In PALASM, the original design specification is entered as a Boolean entry design file,
List 1. First comes a documentation field
giving the user information about the design. After the reserved word CHIP the
assembler expects to see a single description
word, in this case DECODE followed by the pal
type, PAL12L6.
Next is the pin assignment or input constant declaration section. Any string
constant equations may also be declared
here, but no string constants were used in
this specification. The assignment section is
terminated by reserved word EQUATIONS.
All the Boolean equations are written in
the equation field up to reserved word
SIMULATION. From these equations PALASM
generates a fuse plot and Jedec* output file
This file can be transferred to a pal programmer through an RS232 serial interface
using a software -programmable interface
package. The Jedec fuse -plot standard is
favoured by most programmer manufacturers.
To generate test vectors automatically
from the design, the designer can write a
simple simulation program to exercise set
.
*Joint Electronic Device Engineering Council's

'Standard data transfer between the data preparation system and programmable logic device programmer'.
and reset functions on some or all inputs of

the pal. When running the simulator, logic
inputs and outputs can be traced using the
option to verify whether or not a

design will function correctly before cornmiting it to the pal's fuse array.
The hardware analogy is the logic analyser
where probes are tied to nodes in the circuit
and a multiple signal trace is produced on a
c.r.t. With PALASM, test vectors are generated as logic high or low conditions in a
tabular form. Using software called VTRACE a
graphical waveform output can be generated, Fig.9.
All possible input combinations, shown in
Table 5, are generated in the simulation
section of the design specification as SET and
RESET (more accurately SET and INVERSE) operations on NA and sIzo,I.
Running PALASM2 on an IBM p.c. or
compatible system is quite straightforward.
The program is menu driven and prompts
the user for commands.
Once the designer has created a design file
with a text -editor package, the file may be
assembled into a fuse plot as shown in
Table 6.
If a simulation section is included in the
TRACE ON
specification file, then selecting 'simulate'

from the menu results in the generation of a
further three files containing test vectors.
One file is the Jedec programmer file with
the test vectors appended to the end of the
19
18
11
17
16
17
Product
terms 0-63
24
25
16
32
15
33
14
40
41
13
51
12
11
Interna numbering
for fuse plot
12
13
16
17
20
21
24
31
Fig.8. Logic diagram of the PAL12L6. Each And gate has many inputs each connected to
one vertical line by a fusible link.
fuse -plot information. The second is a trace

file containing all test vectors generated for
input and output pins that are qualified by
the TRACE ON command. Thirdly, a history file
containing a full test -vector plot of logic
high and low conditions on every signal pin
in the pal is produced.
Test vectors are appended to the end of the

Jedec file so that the pal may be functionally
tested after programming has taken place.
The programmer sequentially exercises inputs from the individual vectors and compares the actual pal output conditions with
those logic states supplied by the current
test vector.
Writing of the simulation to generate test

vectors is similar to writing commands in a
high-level language program. Logic conditions to input pins can be set high or low by a
command; SETF A will set input A high

and conversely SETF/A sets it low.
For repetitive events, a FOR LOOP directive
may be used; <FOR N := TO 16 Do> causes a
statement or statements between BEGIN and
END to be executed 16 times. Conditional
branching or control is possible with IF or
WHILE directives. A more comprehensive
guide on writing programs for test vector
generation is given in chapter five of the
MMI Programmable logic handbook mentioned later.
With the data-byte selector design,
PALASM2 has provided a route from logic
design to silicon and the simulator gives the
designer confidence in the functional integrity of the design. Using a pal in this
application has saved approximately six dil
packages and simplified printed -circuit
board, layout.
SETF
Further reading
Programmable -logic handbook, MMI, Lynwood
House, 1 Camp Road, Farnborough, Hampshire.
M68020 32 -bit microprocessor user's manual,
Motorola, 88 Tanners Drive, Blakelands, Milton
Keynes MK14 5BP.
Chris Jay is with Monolithic Memories.
69
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MICROSYSTEMS urn 55 Telex 846396
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on the standard bus

An 8MHz 80188 processor,
256 kbytes dynamic RAM, serial I/O
and PROM
for 680! It can run
concurrent CP/M 86, and it interfaces
to the STE bus, the new IEEE P1000
standard for instrumentation and
systems designers. STE is a modern
alternative to buses like STD, but
with many advanced features:
processor -independence, 1 Mbyte
memory addressing, 4 kbytes of I/O
space, and multiprocessor
facilities. It's equally cost-effective in
single -processor designs or
high-performance systems that many
would consider VME for.
Call for details.
Oscom
ONTROL SYSTEMS LTD
Arcom Control Systems Limited

Unit 8, Clifton Road, Cambridge, CB1 4WH
Phone (0223) 242224
Distributors:
Dage (0296) 33200, New-Tek (0223) 211211

CERCLE 49 FOR FURTHER DETAILS
The new standard

for high performance
ion STE
Control Universal, the largest UK manufacturer
of single Eurocard products, have established the
CUBE range as the most popular choice in industrial
and laboratory applications.
Control Universal have now designed Celeste to

maximize the real-time performance of the new
generation of 16/32 bit processors on the STE bus.
,eleste/188
Hardware:
80188 8MHz
8259 PIC
825E MUART
128K: bytes EPROM
64K aytes SRAM
Full system-ccnttr-oller-/b1s,:=
arbit
intltupt-r
-celst-w00$-"
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Hardiwre:
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Control Universal Limited

137 Ditton Walk,
Cambridge CB5 8QF

Telephone (Sales) 0223 2,14447
--64Kbytes
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______
STE
Standard Eurocard bus
Applications of Standard Eurocard bus
range from simple control to multi -processor
systems and all boards are interchangeable.
ANTHONY WINTER
In low -to-medium complexity designs,

STE bus suits the kinds of applications
that buses like STD are currently used
for, but with performance, security and cost

advantages.
Being based on the DIN connector and
Eurocard, STE can be used with other buses
to form relatively low cost multiple -bus
systems. And, in relation to edge connectors,
the DIN connector is more reliable.

Although designed for eight -bit data buses
STE can be used with the latest generation of
8/16 -bit processors. The bus was first specified in 1982, and the first boards were
available in mid 1984. Since then, it has been
widely adopted by board manufacturers.
There are now hundreds of processor,
__>I,_,
\s
peripheral and signal -conditioning modules. Moreover STE is a standard backplane

bus and so you can mix boards from any
sources.
Processing units now available span a
broad application range, with microprocessors from the popular Z80 to newer and
more powerful devices like the 80188, Fig.!.
In the UK so far, STE has an estimated 100
users and at least 18 companies manufacturing boards, backplanes and packaging. Applications range from software development,
through real-time control, to laboratory
computing.
345
,PPNILIPY11iJ
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BUSES ARE CHANGING
r74LS240NCA
aeV98509 F
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more complex v.l.s.i. circuits become

available, backplane buses have grown in
importance helped by their recent improvements in quality. Most growth is in the
high-performance 16 -bit buses such as VME
and Multibus-II, which include advanced
features and are based on the Eurocard
standard and DIN connector.
If you are looking for a standard at lower
performance levels, however, choice is limited. Two current popular choices, STD
and S100, are edge -connector based, with
outdated signal schemes originally designed
for a single 8 -bit processor family. Although
they have been modified to take account of
more advanced processors and large memories, the patches are showing.
The situation is similar with Eurocards.
Thre are dozens of single -Eurocard buses
____,_
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but almost all are designed for a single

processor family and intended for simple
one -processor systems. Here, none has
emerged as a standard with worldwide use
and support.
A typical example is G64, which uses
Motorola 6809 signals. The G64 bus has now
been 'enhanced' to cope with other processors, often at the expense of compatibility
with earlier designs.
STE was originally conceived as a Eurocard replacement for STD. It is similar to
VME, and can be viewed as an 8-bit version of
that standard but, unlike VME, STE has been
designed from scratch to be an independent

bus, suitable for a broad range of processors
and tasks.
BUS ATTRIBUTES
The STE signal scheme may be summarized

as an eight-bit data path, with 1M -byte of
memory space, 4K -bytes of i/o space, asyn-
chronous data transfer, board position independence, multiple master capability

and inter -module flags for interrupts or
d.m.a. Using Eurocard form boards with
64 -way (rows A/C) DIN connectors makes
STE reliable.
An eight -bit data path is used, but this is
not a disadvantage. There are already good
bus standards for 16 -bit data paths like VME
is no standard eight -bit Eurocard
bus. Also, STE goes beyond most existing
eight-bit buses in two respects. First, it can
accommodate the latest generation of eight bit processors, and of course, most 16 -bit
processors are also made in eight-bit versions. Secondly, the bus has multiple master capability; up to three processors
may work in a system. Another point worth
noting is that almost' all peripheral i.c.s are
designed for eight-bit operation.
The bus is equally at home in simple
systems with a single processor and a few
expansion modules. Used as a vehicle for
systems using familiar and popular processors like. the Z80, it suits applications for
which STD is currently being used.
Another advantage of STE over STD is the
expansion potential given by the Eurocard
packaging. The bus can be used alongside
VME as a low-cost i/o channel for instance,
or as a local bus for processing.
Many systems are hampered by the restricted addressing ranges of earlier buses,
which were generally designed around processors limited to 64K -byte. STE provides
two separate addressing fields; 4K -byte of i/o
locations and a 1M -byte memory addressing
space.
Processors like the Z80 can switch the top
four address lines with a latch. This form of
bank switching is used to advantage in
operating systems like CP/M-plus, which
uses this extra memory to speed up disc
operations by a significant amount.
Input/output capability is similarly large.
Twelve i/o address lines provide 4096 i/o
locations, enough for most conceivable
small -to-medium systems. Processors with
no i/o space, like the 6809 pr 68008, can set
aside a 4K memory block for bus i/o accesses.
A significant problem with nearly all buses
is their inability to work with boards designed later in the standard's life. This is
primarily because most buses use synchronous operation.
Data from a peripheral board, for example,
must be available to the c.p.u. within the
defined time. Processor speeds are currently
doubling every four or five years, and
peripherals may not be able to keep up.
To overcome this lifetime limitation, STE
uses asynchronous handshaking. For example, slave boards need to acknowledge that
they've received data from a master. This has
two main advantages. It makes it easy to
interface devices of differing speeds, and
provides technology independence. As better
devices become available, they will still work
with boards based on earlier technology.
but there
STE
compared with other popular backplane buses.
Feature
STE
STD
G64
Signal lines
Address range
Data path
I/O space
Multiple masters
64
56
64K -byte'
64
8 bit
1K -byte
Error checking
Primary board size
Connector
error line
100x 160mm
256 -byte'
off -bus
connection required
none
114x 165mm
Edge
1M -byte
bit
4K -byte
8
up to 3
DIN
64K -byte
bit
yes
yes
100
160mm
DIN
'various expansion schemes
CONFIGURING STE
MASTER
Users of only modest experience should be

able to assemble systems successfully. STE is
free from 'levels of compliance' which means
that all boards are compatible with all other
boards and no slots are reserved. Boards are
Activate address lines

assert ADRSTB after is
truly position -independent.

Another feature is STE's multiple processor or multi -master ability. Up to three
processors may reside on the bus, taking
control of the common bus resource after
going through an arbitration procedure.
Typically, masters are c.p.0 boards and
d.m.a. devices. A bus slave must be able to
respond to bus signals to produce an acknowledge signal when addressed.
The bus is used for communicating between boards, for example to transfer data or
handle interrupts. Often, if there is enough
circuitry on one board, a master can do its
processing locally, freeing the STE bus for
other masters to use.
For example, the Arcom SC88D board
includes an 80188 processor, 256K -byte
ram, and serial i/o. It only needs to use the
bus to program an eprom or, say, read a
value from an a -to -d converter module.
Simultaneously (within a microsecond or
so) another c.p.u. could be processing the
converter values stored in ram on a common
memory board.
Using multiple processors allows highly
fault -tolerant designs to be made or reduces
the cost of high-performance systems by
allowing several simple low-cost masters to
take the place of an expensive state-of-theart c.p.u. board.
The STE specification permits up to three
bus masters, one default and two others
termed 'potential'. A default master is a
board with a bus arbiter and a master, for
example a c.p.u. The bus arbiter deals with
requests from the master on its own board
and from any other potential masters in the
SL AVE
Decode address
Activate command lines

assert DATSTB after is
Decode command
is
-setup
time
Activate data lines

assert DATACK after is
Accept data
release ADRSTB and DATSTB
Release address lines

release command lines
Disable data bus drivers

release DATACK within th
th - hold time
LBegin next operation
system.
DATA TRANSFER
An important feature of STE is asynchronous operation which increases a system's useful lifetime by
allowing mixing of devices of different generations and operations speeds for example. An example of
a read operating illustrates how this works in practice.
Data transfers from a slave to a master are designated read sequences. First, the master places the
address of the memory or i/o location to be selected on the address lines. After a set-up time, during
which the address lines become valid, the master asserts the address strobe noRsrs. The master then
activates the command lines to indicate the type of transfer, i/o or memory read, asserting onrsTe after
an appropriate set-up time, thus indicating that it is ready to accept data.
The addressed slave now enables its bus drivers, placing the requested data on the data lines, then
asserts onrcx after a set-up time to indicate that data is available. In response to this signal, the master
accepts the data and then releases n5RSTe and onisre. When the slave sees this operation, it disables its
data bus drivers and releases oeTecx to indicate a completed sequence.

No time restrictions are placed on this operation, but designers have the option of specifying an 8s
timeout value, which serves to notify the c.p.u. of a board failure.
73
Bus arbitration works at high speed so

that if the bus is free the master requesting it
will be granted access without unnecessary
delay, typically 125ns. If the bus is busy,

there may be a delay of a few hundred
nanoseconds while the new master takes
control, and the arbiter ensures that no
contention takes place during this process.
A system error signal provides integrity of
data transfer. This is asserted by the system
controller if an acknowledge is not returned
within a reasonable period of time. The
signal can also be asserted by a slave should a
local error occur during a transfer.
Integrity of the bus is also aided by careful
layout of the signal lines on the DIN connector to facilitate connection while minimizing crosstalk. Ground lines are evenly distri-
buted across the connector. Another contributing factor is increased reliability compared with edge -connected arrangements
through use of the two-part DIN 41612
connector (64 -way, rows a/c).
There is an intricate system for dealing
with inter -modular communication, using
up to eight 'attention -request' lines. Such
communication usually occurs when interrupts or d.m.a. signals need to be processed,
although the STE bus specification does not
limit designers to these.
Interrupts can be processed in several
ways. At the simplest level, no acknowledge
is necessary (a power -fail interrupt for example), and an attention -request line is
asserted (pulled low) by the interrupting
module. With a common interrupt, the
interrupting module is acknowledged by a
read or write operation on one of its registers; this is also easy to arrange.
Bus -vectored interrupts are the most
powerful. Here, an interrupt handler uses
the command modifier lines to indicate an
acknowledge cycle and puts the encoded
attention -request line number onto the
address bus as a three-bit address. The
module which interrupted on this attention request line can then put an interrupt vector
onto the bus, which the handler reads in the
acknowledge cycle.
PACKAGING
Boards for STE can be either single or double
Eurocards, though the single card is the
preferred size, and is expected to be used by
the majority of suppliers Board depth is
160mm and extended versions are not
accommodated. Small boards allow a high
degree of system partitioning, i.e. they allow
boards performing a narrowly -defined function such as digital i/o, serial i/o, memory
etc. to be used which conceptually simplifies
the system and eases fault-finding.
However some modules, especially processor boards, can be very high -density. This
allows the board to work with few bus
Standard progress
Specification of STE is nearing completion. The
P1000 Working Group, formed at the request of
the IEEE Microprocessor Standards Committee,
recently voted to accept draft 3.2, and the
standard is now awaiting final approval. We
should see publication in late -1986.
74
STE BUS PIN -OUT

Below is the 64 -signal STE bus pin -out defined on rows a and c of a DIN41612 connector. Address lines
provide 1M -byte of main -memory addressing. Depending on the cycle, A0.11 are used to address
the 4K -byte of i/o space and A0.7 provided a three -bit ackowledge address.
Lines D0.7 are the eight bit data bus. Signals AORSTB and DArsre are address and data strobes. Lines
CM0_2 define the type of bus cycle in progress, i.e. whether it is memory or i/o read or write, or an
acknowledge; three codes are free for future expansion.
Request lines BUSRQ0,1 are for use by temporary masters, BUSRQO being higher priority. The bus is asynch,onousand DATACK is asserted when a master accepts data (on a read cycle) or when its data is valid (during
wnte) signalTFERR is used if data from a slave is wrong.
Signals 11io.7 are attention -request lines and Svsc1K and
3sr are for 16Mkz system clock and reset
functions. Remaining lines are for power with fully distributed grounds.
A0.19
s-,
avoiding the potential bandwidth

limitation that any bus imposes and thereby
increasing system-throughput potential.
Most users buy boards off -the -shelf, but in
some cases specialized i/o is required. With
STE bus, making special i/o is relatively
simple because the majority of protocol
conversion circuitry required for interfacing
is concentrated on the master c.p.u. boards.
These boards are the ones most likely to be
bought off-the -shelf and designed by a specialist board maker.
To interface a simple slave i/o board is
relatively easy. A design has been published,
by the STE manufacturers and users group,
and prototyping i/o boards, are available
from Arcom.
accesses,
APPLICATIONS
Where will STE be used? The answer is in all
areas from data -acquisition and control to
information-processing applications. These
areas range from those currently catered for
by STD to many of the less demanding VME
applications.
Simple data acquisition and control systems are a first example. Being single Eurocard, STE allows the same kind of system
partitioning as STD, but it can be used for
simple control as well as for advanced 8 -bit
processor and multi -processor systems. An
example is a Z80 c.p.u. running a disc
operating system such as CP/M Plus on the
same bus as a secondary Z80 board doing
real-time process control; both these boards
are available.
Data processing systems are another application for STE bus. Reliable rapid movements of large data blocks are possible using
d.m.a. transfers and STE has a large memory
addressing range.
For example, Arcom's SC88 can access
1M -byte of memory on the bus directly, and
uses the on -board d.m.a. system to transfer
data from the floppy and s.c.s.i. controllers
at high speed, powerful operating systems
like Concurrent DOS from Digital Research
can be used.
Being capable of accommodating advanced processors and having other advanced
design features, STE will certainly take some
of the lower-level applications for which
VME is often considered. It goes a step
further, however.
Eurocard compatibility means that designers will be able to mix buses in a system for
the best cost/performance ratio.
By selecting STE as an i/o channel for
instance, you can cut costs by removing the
unnecessarily complex bus -interface circuit -
Pin
Row a
Row c
ov
ov
+5V
+5V
D2
D4
D1
D3
DS
6
7
AO
A2
ov
A1
A3
A4
10
A6
11
443
A5
A7
12
Alo
13
Al2
A31
A34
A13
14
15
16
17
18
19
A16
A15
A18
A17
CMp
A19
CM2
(
A9
CM1
ADRSTB
OV
39-ffltrt
oV
20
21
22
23
ATNRQo
SYSRST
KeRQZ
ATNRQ1
ATNRQ4
ATNRQ3
MN%
A3
24
25
ATNRQ6
26
ov
ATNRQ7
27
BUSRQp
BUSRQ1
28
BUSAKa
29
SYSCLK
30
-AUXV
+AUXV
31
+5V
+5V
32
ov
+VSTBY
ov
ry of VME which also increases the system's

effective bandwidth by removing slow or
lengthy i/o transfers.
Boards with dual -bus interfaces for this
new kind of architecture have been appearing for around two years and you can now
buy a VME-to-STE interface board for dual bus systems. You will probably soon see a
VME board with secondary STE bus interface
on the second connector.
Anthony Winter is with Arcom Control

Systems in Cambridge.
. J
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'lt!
COMPREHENSIVE STE bus HARDWARE SUPPORT

As you'd expect from a company with BICC-VERO's
reputation, we're supporting fully the increasingly
recognized STEbus architecture.
We offer you STEbus backplanes, terminators,
extenders, and prototyping boards with interface,
all complying fully with IEEE Standard P1000, Draft 3.2.
our comprehensive range of STEbus
better still
And
support products includes all the additional hardware, fully
compatible with STEbus, you need to build your STEbus
system. The range includes:Power supplies: Single or multi -output plug-in
modules, or open frame switchers, up to 500 W.
Prototyping boards: A wide range of general
purpose boards, plus PTH microboard and Speedwire with
STEbus interface.
Cardframes: Choose from the well-known industry
standards, KM6 or KM7.

Racks and enclosures: Of all types, to suit your
STE application.
Connectors: An extensive selection of two-part IEC
603-2 (DIN 41612) connectors, including pressfit.
Contact us now for more information on our STEbus
hardware support products.
For immediate action, phone: 04215 60211 (South)
or 0744 24000 (North). Or write to:
BICC-VERO Electronics Limited, Flanders Road,
Hedge End,
SOUTHAMPTON, SO3 3LG.
Tel: 04215 66300.
B'CC' ELECTRONICS
Fax: 04215 64159. Telex: 477984
VERO
LEADERS IN STEbus TECHNOLOGY

A MEMBER OF THE STE
MANUFACTURERS AND USERS GROUP
VIDEO FRAME STORE

With this versatile unit, video images can be captured,
processed and displayed. Later articles will introduce the
rapidly developing field of image processing and analysis.
D.E.A. CLARKE
future developments in robotics
and industrial automation will involve
the application of image analysis techniques. Image analysis is becoming necessary
because the limitations of dumb sensors and
mechanical actuators in the current generation of industrial robots restricts their use to
only the most basic of repetitive, well -ordered
tasks.
The addition of vision sensors with interactive computer image processing dramatically increases the range of useful tasks a
robot can accomplish and enables it to compensate for the disorder of the real world.
An ability to acquire and process images
electronically is useful in many other fields.
For example, an image can be stored, manipulated and transmitted over an ordinary telephone line at a rate the limited bandwidth of
today's analogue telephony circuits can handMany
76
le. Thus, an X-ray picture can be digitized and

transmitted from one hospital to a specialist at
another for diagnosis, and the image enhanced using computer techniques to bring
out relevant features and mask unwanted
ones. Similar techniques are useful for remote
surveillance and finger-print matching, for
example.
Once a computer has the means to acquire
and process an image and to display the result,
these and many other exciting applications
become possible.
APPLICATIONS
The original impetus for this project came
from an idea for fund-raising at a Christmas
bazaar. The scheme was to use a tv camera, a
frame store and a computer to print portraits
on a standard dot-matrix printer.
The prototype frame store was constructed
and a program written to print portraits such

as that in Fig.l. Experiments with dot patterns for simulating grey scale and pixel dither
for smoothing contours proved interesting
and I shall discuss these techniques in a later
article.
Weather satellite pictures are transmitted
in the 136-138MHz band by polar orbiting
satellites. Decoding methods for these broadcasts have been described in Electronics &
Wireless World and construction kits are
available: but the full range of grey levels
cannot normally be displayed on a low-cost
computer.
Displaying the received pictures on a
monochrome monitor using a frame store is
an attractive alternative. The full range of 256
grey levels gives a high quality tv picture
suitable for photography, such as the example
shown in Fig.2. The computer can be used to
enhance certain features and a colour look -up

table may be programmed with a suitable
range of colours for display on a colour
monitor.
Figure 3 shows an X-ray plate which was
captured with an inexpensive tv camera. The
contrast has been boosted and the result
stored on disc, along with the original image,
for future reference.
Version shown here (on top of monitor) has the colour palette fitted.
Fig.1. This 16 -level image was reproduced by a
dot-matrix printer.
3-D DISPLAYS?
Commercial units are now appearing which
exploit the dual image nature of interlaced
raster-scan displays to produce pseudo-threedimensional effects. The principle is simple:
each of the two fields which constitute a frame
is arranged to be a separate view of the object,
as would be seen by each eye of the viewer. The
viewer wears liquid crystal spectacles which
blank each eye alternately in synchronism
with the field scan of the tv monitor, thus
producing a 3-D illusion flickering at 25Hz.
With the enhanced frame store in 512 x 512
(interlaced) mode and a pair of the special
l.c.d. spectacles plus scan interface, the user
could try interesting experiments with
computer-generated 3-D images.
Another possibility (which I have not tried),
might be the generation of 3-D illusions with
alternate fields in different colours (say red
and blue). Cheap spectacles with appropriately
coloured filters for each eye (such as those
issued for recent 3-D broadcasts on tv), may
give a similar illusion. To implement this
77
scheme, the colour palette board to be de

scribedin a later article would be used to
switch colours between successive fields.
These applications are a few I have experimented with; others such as slow -scan tv,
surveillance, picture processing I leave to your
ingenuity.
Fig.5. This prototype system is built on single -height Eurocards.
video sources
r
-1
"tom 'or
Frame
store
Videa
TYPICAL INSTALLATION
small system (Fig. 4) might comprise a basic

frame store (with or without a colour palette),
a black and white tv monitor (or a domestic tv
plus u.h.f. modulator) and a computer with an
eight-bit parallel output port and a bidirectional eight -bit parallel port. The frame
store could then be used to display weather
satellite pictures, slow -scan tv pictures or
high quality computer generated images.
However, any source capable of providing
1V peak -to -peak video would be suitable: this
could be a tv camera or even a video cassette
recorder. Images could then be captured,
stored, manipulated and displayed.
With the colour palette option, spectacular
colour effects can be achieved on an r.g.b.
(t.t.l. or 1V p-p) colour monitor.
The unit has a manual freeze switch, so it
could even be used without the aid of a
computer to produce amusing strobe effects
with a tv camera, for example.
Second-hand tv cameras can now be easily
obtained for well under 100 and are the ideal
video source for experimenting with image
processing.
The frame store described here is of the
variety commonly referred to as a frame
grabber. The frame grabber is distinguished
A
78
uuiiiiii
Computer (optional)
Manual
freeze
picture -processing system. The frame store can instantaneously

picture from any standard video source.
Fig.4. Layout of a basic
capture
by its ability to acquire a tv image in a single
frame interval. Other less versatile designs use

slow analogue -to-digital converters with
sample -and -hold amplifiers, and acquire the
image over several seconds. They have the
disadvantages of slow capture rate with consequent loss of definition on moving or unstable
parts of the picture.
The present unit suffers from none of these
disadvantages and yet is simple to build,
operate and expand. Two key developments
have made it possible:
- the arrival of cheap, high density (64K and
256K) static rams, which has simplified
control circuitry, reduced power consump-
tion and eased computer interfacing.

the recent introduction of low-cost `flash'
analogue to digital converters (a.d.cs) and
fast digital to analogue converters (d.a.cs)
with high resolution (7/8 bits) at video
rates.
COMPONENTS
semiconductors for this project will be
available from Technomatic Ltd, 17 Burnley Road,
London NW101 ED.
The video converters (PNA7518 and PNA7509)
have proved popular because of their low prices
and may be in short supply. It would be advisable to
order these parts early.
A kit of
FEATURES
single frame acquisition from tv camera, v.c.r.
etc.
resolution (64K ram):
256 x 256 x 128 -bits
(8 bits displayed)
resolution (256K ram):
512 x 512 interlaced

512 x 313 non -interlaced
variable sampling frequency (to over 11 MHz).
with variable sampling window.
computer interface for read/write access to
frame memory
colour palette option:
16 colours from palette of 4096
- t.t.l. r.g.b. outputs
-1V p -p r.g.b. outputs
external r.g.b. inputs for programmable
colour -keying on main picture
dual image storage in 512 x 512 mode.
modular construction allowing retrospective
enhancement.
Link options enable straightforward upgrading to
256K rams when their cost becomes reasonable.
a)
b)
The latter has been brought about by developments in digital television technology and the
need to produce low-cost digital signal processing circuitry for the new generation of tv sets.
Fig.2. Weather satellite picture from NOAA-9 (1 August, 1986), showing a large weather
system directly over the UK. France and the Bay of Biscay are visible at bottom right.
CONSTRUCTION
The basic unit can be constructed on five
single -height Eurocard breadboards as follows:
1 Data conversion and signal conditioning
board with an on -board video test gener-
ator.
2
Control and computer interface board.
3 Static ram board: 64K -bytes, upgradeable
to 256K -bytes.
4 Colour palette board (optional)
supply board (optional)

The frame store is shown as a block diagram
in Fig. 6. The colour palette can be added at
any time after the basic system is constructed.
Spectacular real-time video effects can be
achieved with simple devices such as adders
and shifters connected to the video bus.
Alternatively, extra memory, an arithmetic
logic unit and control circuitry could be added
to achieve real-time image manipulation or
time -averaging for noise reduction. Such
enhancements will be the subject of a further
series of articles.
The host computer interface consists of
eight control lines which would typically be
connected to an eight-bit output port. Data is
transferred to and from the memory via an
eight-bit bidirectional port. A push-button
freeze control has been found very useful for
setting-up and operating the unit.
5 Power
Fig.3. Image processing applied to an X-ray plate: the original image (left), and (right)
contrast -enhanced version. Note extra detail at bottons right.
Fig.6. Block diagram of the frame store. The colour palette option offers 16 colours from
a
range of 4096.
+
+1ov
RGB
politics.
video
peak to peak
video
Overlay video
1V
RGB
Cajou
palette
+5V
+10V
Video i/p
Video
converter
Control
e-
Sync
8
4
-SV
Data
Control
Freeze
Host
Address
computer
Don Clarke is an electronics engineer in the

telecommunications industry. After studying for an HNC at Colchester Institute whilst
working as a trainee technician, he went on
to Essex University where in 1981 he gained
an honours degree in computer systems.
Leisure interests include preserving historic
buildings, the technical side of theatre, and
RGB
Control
To be continued
Control
Data
Memory
64k/256k
+5V
a c. input
+5V
Video
effects
i
ii
n
1
800mA
+10v
250mA
low ripple
Power
supply
1
79
Analytical
Software for
Electronic
Engineers
from "Those
Engineers"
INDUSTRIAL
STE
INTERFACES
THOSE ENGINEERS,
formerly Seasim
Engineering Software,
have moved. Please note
our new address: Those
Engineers Ltd, Unit D1,
Fairoaks Airport, Chobham,
Surrey GU24 8HX.
Tel: Chobham (09905) 6565
FOR MS DOS COMPUTERS (256k+ RAM recommended)

(state computer type when ordering)
ECA -2's 1986 edition expands the analytical power of the original to include Fourier
analysis and sweep commands and adds graphics output to include Bode plots, DC transfer
curves and transient timing diagrams. ECA -2 is now the most potent analogue circuit
simulator available. It offers friendly interactive control and an optional batch mode. A
proper diode model. temperature effects, bias & operating point analysis, a transmission
line model, non-linear effects wherein polynomials (to any order) or piece -wise linear
characteristics are supported. Tolerances are used to compile worse case and Monte-Carlo
analyses. Macro -models, complex models (eg capacitors with inductance and resistance)
may be used. Voltages, currents, dissipations and power volts (a useful transistor
secondary breakdown indicator) may be looked at anywhere in the circuit. Similar flexibility
is offered for the input to a circuit which may come from a file or the output of a previous run.
Sparse matrix techniques allow ECA -2 to model typically 500 nodes in a circuit (depending
on memory available). Price: 465 + VAT incl. p&p. Updating service available, please ask
for details.
EC -Ace is a subset of ECA -2 also offering AC, DC and transient analysis and high quality
graphics output. Although it lacks some of the more advanced features of ECA -2, it can
accommodate a very useful 100 circuit nodes and is available at the irresistible price of 110
+ VAT incl. p&p. Upgrade to ECA -2 available.
For the BBC MODEL B, B+ and MASTER

(State 40 or 80 track when ordering)
Microspice. This
Kemitron's new range of STE boards is a

real breakthrough. Each one is packed with
features which reduce the board count and
increase reliability. Our rear termination
method eliminates yards of ribbon cable
and allows boards to be withdrawn without
disturbing plant wiring. Just some of the
new range include:
SPC-180 Processor
HD64180 CPU (Z80 code compatible) 6MHz.
with DMA and 2Mb addressing, 4 Serial,
RTC, timers, watchdog, maths processor. Floppy disk
controller, hard disk interface. STE bus
768K16 RAM/ROM
SDC-180 Digital I/O

32 User configurable input/output/counter/timers
Opto -isolated I/O, Darlington drivers, feedback sensing
10 Channel programmable CTC, opto -isolated, MHz
max. Front panel LED indication of all channels.
1
SAN-180 Analogue I/O

64 Single ended or 32 differential analogue inputs.
Independent analogue outputs. 12 bit plus sign DAC
12 Bit plus sign ADC, I 2.5usec conversion speed Sample
and Hold, programmable gain, current in/out. Front panel
LED indication of channel, status, etc.
8
For full details of the range of boards,

systems and software available from
Kemitron - call us now.
is a remarkable suite of programs for simulating DC and AC analogue

circuit behaviour including non-linear effects. Features such as its transistor modelling (20
parameter Ebers Moll) and an excellent manual have been quietly earning this program a
reputation as the most useful ever produced for modelling small circuits. Price 99 + p&p'
+ VAT. ('E2 UK or 5 overseas.)
Orders accepted from existing customers and educational bodies. Otherwise please send
cheque with order to our new address. You may prefer to contact us through our One to One
mailbox which can also be accessed by telex. Telex no. is 8950511 (ONEONE G) and our
mailbox number which should be quoted at the start of the text is 23332001.
Happy Memories
Part type
4164 15Ons Not Texas
41256 15Ons
2114 200ns Low Power
6116 150ns Low Power
6264 15Ons Low Power
2716 450ns 5 volt
2532 450ns
2732 450ns
2732A 250ns
2764 250ns Suit BBC
27128 250ns Suit BBC
27256 250ns
Low profile IC sockets: Pins
Pence
off
25-99
.95
.90
2.25
2.15
1.75
1.40
2.40
1.60
1.25
2.15
2.60
4.85
2.40
2.85
2.20
2.60
3.45
2.75
5.40
2.60
3.30
2.45
2.75
3.70
100 up
.87
2.05
1.55
1.20
2.05
2.45
4.50
2.25
2.75
2.05
2.40
3.30
8 14 16 18 20 24 28 40
5 9 10 11 12 15 17 24
Please ask for quote on higher quantities or items not shown.
Data free on memories purchased, enquire cost for other.

Write or 'phone for list of other items including our 74LS series
with DIY discounts starting at a mix of just 25 pieces.
KEMITRON
INDUSTRIAL
&
SCIENTIFIC COMPUTERS
Kemitron Limited,
He
warden Industrial Park, Manor Lane,
Deeside, Clwyd CH5 3PP

Telephone: (0244) 536123 (6 lines) Telex: 61471
Please add 50p post & packing to orders under 15 and

VAT to total. Access orders by 'phone or mail welcome.
Non -Military Government & Educational orders
welcome for minimum invoice value of 15 net.
HAPPY MEMORIES (WW),

FREEPOST, Kington,
Herefordshire HR5 3BR.
Tel: (054 422) 618
80
VEW PRODUCTS
Remote controlled
oscilloscope
Multifunction
calibrator
An infra -red remote controller,

similar to that used with tv sets has
Datron has produced the 4700

Autocal calibrator which offers direct
and alternating current and voltage,
and resistance ranges of a suitable
accuracy to calibrate mid -range 5.5
and 6.5 -digit d.m.ms. It can be used
by itself or automated into a
calibration system. Also from Datron
is a range of pulse generators and
waveform analysers.
237 on reply card
been added to the 350MHz Philips

PM3295 to produce the PM3296. The
remote unit permits the selection of
up to 25 front panel settings
(optionally expandable to 75). Each
setting must be preset manually or
through the GPIB, rather like tuning

the tv, and a `save' button on the
hand unit is pressed to store the
selection. Each setting can then be
recalled by dialling the appropriate
number on the remote controller.
This facility is useful when there is no
need for an external controller, for
routine measurements, particularly

in conditions where it may not be
possible to touch the instrument.
Examples are in climatic chambers
or in high -voltage environments.
To make this possible all the
internal controls on the oscilloscope
have been digitized, including the
rotary potentiometers. The
instrument, like its predecessor has
two input channels, real and delayed
timebases, trigger view and versatile
triggering.
220 on the reply card
Microwaves
counters "2/3
competitors price"
20MHz oscilloscope
Latest in the Hameg 203 series is the
203-6 a dual -trace oscilloscope with a
20MHz bandwidth and a maximum
sensitivity of 2mV/division. It is
possible to display the sum and
difference of two signals. Triggering
facilities include h.f. (up to 40MHz)
and d.c. as well as line and tv sync
triggering. The time resolution is
2Ons/div. including a 10x
The Systron Donner division of

Thorn -EMI have a new signal/sweep
magnification. The c.r.t's internal

graticle gives parallel -free viewing
over a wide angle. The instrument
has a built-in component tester with
test voltages and currents at a
suitable level, for in-circuit testing
and semiconductors. The
oscilloscope was designed for general
purpose use and it ease of use makes
it suitable for training.
Two new microwave frequency
counters operating are also being

introduced, to be sold at "two-thirds
the prices of competitive
equipment."
Also new is the Model 1720
microwave signal synthesizer which
provides precise signals between
50MHz and 18GHz from a single
output connector. Automatic
internal and external levelling
control provides "extremely flat
response over the full frequency
range." Accurate control, from -100
to + 10dBm, is provided by a step
attenuator and vernier control.
236 on reply card
Precision
capacitance bridge
Digital pulse and

delay generator
Five picoseconds is the claimed
resolution of the Stanford DG535
delay/pulse generator. It has four
separate delay channels each with a
1000s range. The internal trigger can
be operated in single -shot or burst
modes and is programmable from

0.001Hz to 1MHz. The output levels
are continuously adjustable to
precise settings but can also be seen
to select standard levels such as t.t.1.
or e.c.l. Both high and low
impedance loads can be driven with a
slew rage of 1V/ns. The four outputs
can be programmed directly through
the front panel with confirmation of
all settings on the display. Delay
levels can be entered individually or
linked to follow each other in any
desired sequence. A non-volatile ram
can hold up to nine instrument
settings which can also be set by
computer through the GPIB.
Available through Lambda
Photometrics.
generator which can be externally

programmed for automatic testing.
Audible logic probe

In addition to the standard green/red
leds, the 610B logic probe offers an
audible bleeper to indicate high or
low state, pulse state and pulse trains
above and below 200kHz. Suitable

for both t.t.l. and c-mos circuits, the
minimum detectable pulse width is
3Ons. Exclusively in the UK from
Global Specialities.
360 on reply card
Eight-digit accuracy with a

resolution of 1ppm or 0.5attofarad is
possible with the 2500 capacitance
bridge, from Lyons Instruments.
Stability is lOppm/year.
Measurements are made at 1kHz
over the range -0.015F to
+0.154 (microsiemens). Eight
digits are displayed but up to nine
can be sent to a remote device.
The instrument is a true ratio transformer bridge incorporating a
fused -silica reference capacitor. Four
different loss units plugs deviation
measurements are provided,
averaging time and maximum test
voltage are selectable. RS232, GPIB
and scanner interfaces are provided
and allow internal corrections and
calibrations against an external
standard to be performed
automatically. Apart from its use in
metrology and component
measurement, the instrument can be
combined with the appropriate
transducers to measure a wide range
of physical phenomena.
81
DATABANK
ADVANCE
BRYANS
ANALOGIC
LTD
INSTRUMENTS
Advance Bryans brings you the best of all worlds in oscilloscope

operation: The DS. 1520 series has a 20MHz bandwidth for normal
dual channel real time applications. as well as an advanced 2MHz
digital storage specification. The many sophisticated technical
features some unique
result in outstanding performance and
versatility for an instrument in its price range.
Four versions are available giving hard copy output to Advance
Bryans XY recorders or digital plotters as appropriate.
Analogic announces a new catalogue of data conversion rroducts as

part of its programme to remain a world leader in high speed-high
accuracy data conversion products. exemplified by the Adam 826 a
16-bit half megahertz ND converter which sells for approx. 600.
The company intends to be aggressive and has appointed distributor Consort Electronics to provide increased service to cus-
tomers.
14pm Srorage Osot n<op-,,
DS t520sene.,
20 MI, Red ro,r
MHz 0.n no, Brom).
CIRCLE 34
CIRCLE 55
FOR FURTHER DETAILS.
MS
COMPONENTS
P.S.P.
LTD
P.S.P. Electronics have updated their free short form literature
which includes photographs and information about their complete
The latest edition of the MS components catalogue features 1.1100

new product additions. Bringing the total to 10.000 line items. All
products are priced. In stock and despatched on the day of order.
The 316 page catalogue details batteries. power supplies. books.
cable, capacitors connectors. fuses. circuit breakers, hardware.
indicators, meters. instruments, modems, opto, relays. resistors.
security, semiconductors, service aids, soldering, suppressors,
switches, tools and transformers.
range of connectors,
The literature is in full colour, includes stock range additions
such as the Sounau 651 series, and can be obtained by circling the
number of the Free Product Information card.
N.S.Y. is a franchised distributor for ITT Cannon. Thomas &
Betts. Transradio, ITf Pomona Electronics, Panduit and Souriau
and. as always. P.S.P. are able to provide technical advice and services to meet clients' particular needs.
Manufacturers' catalogues with full product specifications can
also he supplied on request.
CIRCLE 56
CIRCLE 66
ELECTRONICS & WIRELESS WORLD
DATA
BANK
let your brochure do the selling
Databank is the small space with the big selling opportunity.
At less than
1/5 of a penny per reader, it's guaranteed to be the most

cost effective way of reaching your potential customers.
Or, as a special offer, book 3 or more insertions and the cost will be just
200 each. Whichever you choose, it's an incredible offer.
It gets your sales brochure seen in precisely the right place

inside the
covers of Electronics & Wireless World.
And for only 250, you can take an eighth page advertisement in full
colour, showing your latest brochure together with up to 60 words of
description and its own individual reader enquiry number, and reach
over 120,000 potential purchasers.
If you want to get your product information into the right hands fast,
call Ashley Wallis on 01-6613130, or return the coupon.
DATA BANK
Order Form
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Position
Company
Address
Please telephone to discuss my requirements

Please reserve 1/2th page in DATABANK for the
issue,
and telephone to confirm
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L._
82
Published by Business Press International, Electrical-Electronic Press Division, Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS. Telex 892084 BISPRS
G.
(VEW PRODUCTS
Ultrasonic wire
tracer
RS232 monitor
A pocket serial monitor, the
Cablefaker from Compondex, can be
attached to any RS232c port to
monitor the signals. A liquid crystal
displays the line status and the
instrument features a breakout and
patch field together with pulse catch
and positive or negative logic
monitoring. The instrument is
powered from the line and needs no
A diagostic tool from Cablecheck

helps to overcome the risk of damage
to senstive components by using an
ultrasonic method of tracking wires,

indentifying and locating open or
short circuits. Ultratrace consists of
two instruments, transmitter and
receiver. The transmitter is attached
to a suspect wire by a alligator clip
batteries.
and the receiver scans the wire, the

system works through walls and
under floorboards and can trace
cables through metal sheets or other
materials.
Modular meter
The Jay range is claimed to have the
unique ability to accept a series of
plug-in modules to turn the main
and also accepts calibration and

simulation modules. The carrying
case includes a pack of batteries,
re -charged through the instrument.
instrument into a d.m.m,
CIL Electronics Ltd.
temperature, strain or other meter
261 on reply card
NU
aftelftiammaminumemim
Surface mounted
asic oscillator
In our picture, the circular crystal
has been removed to show the
ceramic substrate of the M1000 clock
oscillator. The i.c. includes links to
select the frequency from between 4
and 48MHz, with guaranteed
stabilities of 0.01, 0.05 or 0.1%. The
devices consumes less than 55mA,
and the oscillators deliver a 4V
square wave output, capable of
"Lowest priced
d.s.o."- Hameg
Paxton Instruments distribute the
Hameg range of oscilloscopes
including the HM203-6 dual -trace
oscillosope which has all the features
of the HM203-5 but adds an active tv
sync separator and two probe kits all
for 285 (+ tax). Also making its
debut is the HM205 digital storage
oscilloscope which offers 20MHz
real-time readings and 100KHz
digital sampling. Complete with
probe kits for 448 (+tax) it is
claimed to be the world's lowest
priced d.s.o.
235 on reply card
Dynamic board
testers use d-mos

Dynamic testing of both analogue
and digital products is possible with
the Spea Digitest 100AD. Using easy
to programme multi -mode
architecture, the instrument is
claimed to offer considerable cost
saving in test program generation
times. With the use of very highspeed d-mos electronics, there is a
great reduction in transmission time
delay which eliminates the need to
'descew' the software. The
instrument uses a single -chip driver
as opposed to the driver circuitry of
rival automatic test instruments.
Landis & Gyr Communications.
238 on reply card
driving up to 10 t.t.l. loads. The

output has better than 60/40
symmetry and the oscillator begins
]cock -pulse generation within 10ms
of power up. All is included in a 4 -pin
J -lead surface mounting package.
From MF Electronics Corp in
Scanner/switcher
controlled at the front panel or

through an RS232 port with a local
Up to 512 analogue inputs can be
display to echo the all setup
scanned and switched between the

transducers and analysed/logging
equipment with the Kite Series 16
scanner. The channels are scanned in
a user-programmed sequence in
units of 1, 2, 4, 8 and 16 output to the
analysis system for further
processing. The instrument can be
information including which

channels are currently active.
Lab power supply

New from Thurlby Electronics is the
PLK series of laboratory bench power
supplies. Each has three independent
outputs; a high current 5V output
which can be varied between 4 and 6V
and which incorporates a crowbar
over-voltage protection; The other
two are fully variable between 0 and
30V and can be fully isolated and
independently adjustable or can
track each other so that one control
adjusts both outputs together.

Digital metering has an accuracy of
America.
266 on reply card
Applications include machine health
monitoring, noise and vibration

signal aquisition, testing of
electronics systems and laboratory
multi -way signal routing. Kite
DevelopmentsLtd. 263 on reply card.
10mV or I mA. All outputs are

current limited and protected
against overloads and short circuits.
One of the outputs has fully variable
current controls and can be used as a
constant current source. Line and
load regulation offers less than
0.01% change fora 10% line change
and 0.02% for 100% load change.
Remote sense terminals ensure the
maintenance at the load point
regardless of lead impedance. 60W
and 120W version are available
83
The Archer Z80

-
bC
The SDS ARCHER The Z80 based single board

computer chosen by professionals and OEM users.
* Top quality board with 4 parallel and 2 serial ports,
counter -timers, power -fail interrupt, watchdog timer,
EPROM & battery backed RAM.
* OPTIONS: on board power supply, smart case,
ROMable BASIC, Debug Monitor, wide range of I/O &
memory extension cards.
from 185 + VAT.
The Bowman
-
68000 SDC
The SDS BOWMAN The 68000 based single board

computer for advanced high speed applications.
* Extended double Eurocard with 2 parallel & 2 serial
ports, battery backed CMOS RAM, EPROM, 2 counter timers, watchdog timer, powerfail interrupt, & an
optional zero wait state half megabyte D -RAM.
* Extended width versions with on board power supply
and case.
from 295 + VAT.
Mcrwood Da aytenw Lei

Sherwood House, The Avenue, Farnham Common, Slough SL2 3JX. Tel. 02814-5067
HART
- The Firm for QUALITY
LINSLEY HOOD 300 SERIES AMPLIFIER KITS

Superb, HART designed, integrated amplifier kits derived from
Linsley -Hood's articles in 'HiFi News'.
Ultra easy assembly and set-up with sound quality to please the
most discerning listener. Ideal basis for any domestic sound
systems if quality matters to you. Buy the complete kit and save
pounds off the individual component price.
K300-35. 35 Watt, Discount price for Complete Kit
K300-45, 45 Watt, Discount price for Complete Kit
RLH485. Reprints of Original Articles from 'HiFi News'
SATELLITE TELEVISION
98.79
102.36
1.05 no VAT
LINSLEY-HOOD SYNCHRODYNE AM RECEIVER

Very high quality kit for this recent design featured in 'Wireless World'. Advanced construction
system, approved by the Author. uses 3 double sided PCBs in a stacked layout for total stability, ease
Buy direct from the manufacturers, low cost full

band satellite TV systems.
Complete satellite receiving system from
495.00 + VAT.
Write or telephone for details, or call in at our
factory showroom.
NETWORK SATELLITE
SYSTEMS LTD
of construction and minimal wiring. This module will form the AM section of an ultra high quality
AM/FM switched bandwidth tuner to match our 300 series amplifiers. Power supply and tuning gang
will be included with the FM section.
Special Price 59.95
K450 JLH Synchrodyne Kit
Units 7-8
Newburn Bridge Industrial Estate
Hartlepool, Cleveland TS251 UB
Tel: (0429) 274239 or 869366
LINSLEY-HOOD CASSETTE RECORDER CIRCUITS

Complete very high quality low noise signal handling stages for any stereo cassette recorder.
Separate record and replay sections for optimum performance. Switched bias and equalisation to
cater for chrome and ferric tapes. Very easy to assemble on plug-in PCBs. Complete with full
instructions.
33.70
K800 Complete Stereo Record/Play Kit
8.70
860X Stereo Mic Amp Kit to suit
75p no VAT
REH 8 2 Reprints of Original Articles
1
HIGH QUALITY REPLACEMENT CASSETTE HEAD

Do your tapes lack treble! A worn head could be the problem. Tape
heads are constantly improving and fitting one of our latest
replacement heads could restore performance to better than new!
Standard mountings fit most decks and our TC1 Test Cassette will
make it easy to set the azimuth spot on. As we are the actual
importers you get prime parts at lowest prices. All our heads are
suitable for Dolby machines.
HC20 Permalloy Stereo Head. Good quality standard head filled as original equipment on many
7.66
decks
HS16 Sendust Alloy Super Head. Quite simply the best. Longer life than permalloy, higher output than
ferrite, fantastic frequency response
14.86
HQ551 4 -Track head for auto -reverse or quadrophonic use. Full specification record and play head
14.60
2.49
Special Offer Stereo R/P Heads
3.50
4 -Track Auto -Reverse Play Head
6.70
HS9510 2/4 Stereo DC Erase Head
H0751 E 4/4 Erase compatible with HQ551
39.70
Full data on these and other heads in our range are contained in our free list.
HART TRIPLE-PURPOSE TEST CASSETTE TC1

inexpensive test cassette enables you to set up VU (Dolby) level, head
tape speed without test equipment. Vital when fitting new heads. Complete with instructions
One
azimuth
and
4.66
Send for your FREE copy of our lists with full details of our complete range of Kits, Components, PCBs.
Cassette Heads and Decks: -Overseas please send 5 IRCs for Airmail Post.
Please add VAT to all prices. Postage on orders up to 10- 50p. 10 to 49 - 1. Over 50 - 1.50.
MEELECTRONIC KITS LTD
Penylan Mill, Oswestry, Shropshire SV 10 9AF

24 hr SALES LINE (0b911 bb[t594 Please add VAT
1,
84
SMALL SELECTION ONLY LISTED - RING US FOR YOUR

REQUIREMENTS WHICH MAY BE IN STOCK
Racal Solid State Communication Revel.
van -
Mechanical digit readout 1

Racal RA17L Communication Receivers 500KC/S to 30MC/S in 30
175 - All receivers are air
bands 1MC/S Wide
tested and calibrated in our workshop - operation
with
dust
cover
supplied
instructions - circuit - in fair used condition.
frequency
(Decade
Racal
Synthesisers
1.6MGS to 31.6 MC/S generators) MA250
100. MA1350 for use with RA17 receiver 100. MA259G
precision frequency standard
5MC/S - MC/S - 100KHz 100 to 150. RA137
40
and RA37 LF convertors 10 to980KC/S
to 75. RA98 SSE-ISB convertor - 50. RA121
SSB-ISB convertor - 75. Plessey PR/55G
60KC/S 30MGS - 300.
Solid State receivers
5 level
Transtel Matrix Printers AF11R
for print out on
up to 300 bauds
baudot code
50. Army Field
plain teleprinter paper
RA1217
30MC/S
300.
F L and J - large quantity

- 6 to 15 depending on type and
quantity. P.O.R. Don 10 Telephone Cable Night
half mile canvas containers - 20.
periscopes
- twin
Infra -red
Viewing
eyepiece - 24 volt DC supply - 100. EA.
Original cost to Government over 11,000. EA.
Static Invertors - 12 or 24 volt input - 240 volt
various wattages. P.O.R.
AC sinewave output
various
XV Plotters and pen recorders
P.O.R. Signal Generators - various - P.O.R.
Power meter - 50. Racal
TF 893A
50. Tektronic
frequency counter type 836
plug -ins 1A1 50. 1A2 40. 1A4 100. M 50.
items
are
bought direct from H.M.
All
Government being surplus equipment. Price is
ex works.
S.A.E. for enquiries. Phone for
appointment for demonstration of any items;
also availability or price change. V.A.T. and
carriage extra.
Telephone sets type

in stock
EXPORT TRADE AND QUANTITY DISCOUNTS
JOHNS RADIO, WHITEHALL WORKS,

84 WHITEHALL ROAD EAST, BIRKENSHAW,
BRADFORD BD11 2ER. TEL NO: (0274) 684007
WANTED: REDUNDANT TEST EQUIPMENT -VALVES-PLUGS-SOCKETS,
SYNCHROS ETC. RECEIVING AND TRANSMITTING EQUIPMENT
STEW PRODUCTS
AI and p.c.b.
autorouting
We often read about RISC processors
and what a marvellous contribution
they will make to our futures. Now
we have a practical example: The
Novix Forth processor is being used
in the Calay c.a.d. system for p.c.b.
design. It includes an expert system

artifical intelligence program for
autorouting tracks and can take into
consideration the requirements of
high -density boards with new
component and soldering methods.
Boards with over 1000 connections
can be automatically routed and
optimized 'overnight'. The Calay
system uses a DEC 11/73 c.p.u. and
the Novix processor is incorporated
into a co -processor board plugged
into the Q -bus. A five -fold bus
structure enables five operations to
be carried out in parallel. A designer
is not restricted to a standard set of
design rules and can set up any rules
for a particular board. A special rules
memory hold these and an inference
calculator derives the precise
instructions for the router. A single
pass then implements the
instructions in the layout. It is also
possible to generate automatically
several different versions of the same
layout and select the best or the best
combination to achieve the optimum
layout. The RPR -3 hardware
accelerator can be retrofitted to any
Calay system. UK agents are
Automation Systems Ltd.
Logic analysis on the PC
32 -bit workstation
An interface package and software

allow the Thurlby LA160 logic
analyser to be linked to an IBM PC.
Data is taken from the 16 or 32 -
The new Clipper 32 -bit processor

from Fairchild is implemented on
three chips and can work at a rate of 5
million instructions/s. It is
incoroporated in the 32C desktop
workstations from Intergraph and
claim to be faster than most multi-
channel logic analyser and loaded

into the computer through the
RS232 port. The control program
produces colour graphics on the
computer screen and makes full use
of the computer's facilities to provide
stored records on disc and print-outs
if needed. The screen can display the
timing of 16 channels vertically with
either 64, 256 or 1024 samples
horizontally. The channels can be
named and displayed in any order.

The screen also shows the value of
the cursor and pointer positions and
the difference between them.
Another display mode lists 32 words
of the logic state, rapid scrolling,
word search and comparisons with
test patterns are all possible.
The LA -PC Link consists of a rom
program for the analyser and
software on disc for the computer. A
cable is provided to connect the serial
ports.
Taking a leaf from Amstrad's book,

Acorn have come up with the BBC
Master Compact. This is a cut -down
version of the BBC Master but comes
with a built-in disc drive and a
monochrome or colour monitor.
Another departure is the division of
the keyboard from the power supply
and the 3.5in disc drive which is
housed in a separate box. It lacks
some th of the expansion facilities of
the Masterand has less built-in
software, some of which is included
on the Welcome/utlities disc. It is
aimed at primarily schools and the
home market. 500 (+ tax) for the
colour version.
225 on reply card
D.S.P. with
program memory
The latest digital signal processor
An interactive, computer -aided
or independent electronics
engineers. Available from First
Publishing Ltd. 264 on reply card.
STE -bus industrial
computer
Based on the Hitachi HS64180, an
enhanced Z80 processor, the
Kemitron STE/RIO computer, offers
an STE connector on each circuit
board but also connects through the
company's own rear input/output
connector. The c.p.u. board offers up
to 512K d -ram, 256K eprom, or 96K
Direct memory managment

for up to 2Mb. There are four serial
channels, three timers, a watchdog
timer, real-time clock and battery
floppy and hard disc interfaces and an
STE-bus controller. All is housed in a
standard rack unit. 265 on reply card.
s -ram.
production environments, the more

compact InterPro has one screen for
the normal office environment. Both
have high resolution graphics and
can show 32 colours at one time from
a palette of 4096.
New BBC
Board designer for

Atari ST
design systemf ro p.c.bs has been
developed to run on the Atari 520ST
or 104ST. Its facilities includes
autorouting of tracks, rerouting and
redrawing if required. The program
is intended for the smaller business
processor microcomputers. InterAct

32C has two screens for full-time
Chearest clone (so far)

Claiming to be IBM PC compatible
and running MS-DOS (not PC -DOS)
the Amstrad PC 1512 starts at only
399 (+ tax). The basic model is
monochrome with one disc drive and
512K of ram bug at the top of the
range come a 20MByte hard disc
model in full colour at less than

1000. There is not intention to
produce an AT -compatible model
(yet) and any future IBM
developments are to be ignored for
some years.
from Motorola offers 10.25mips and

56bit operation. The DSP56001
features 512 words of on chip
program ram, two preprogrammed
data roms, two 256, word data rams
and special on -chip bootstrap
hardware to allow easy loading of
user programs into the program
ram. Without the need for preprogrammed roms, the device
becomes an off -the -shelf product. It
offers no contention over the use of
the memory bus. Programs can be
changed dynamically.
The on chip x and y rams come
preprogrammed with A -law and Mu law -to-linear conversion tables and
with a sine table for waveform
generation, discrete and fast Fourier
transformation. The chip has a wide
range of communications interface
ports and seven buses. Applications
include speech and other
communications, instrumentation
and control, image processing and in
navigation. Available for sampling
early in 1987, the device comes in an
88 -pin ceramic grid array package. A
software package of simulator and
macro cross -assembler is available
now. 267 on reply card.
85
LTD
LANGREX
SUPPLIES
Streatham, London
Climax House, Fallsbrook
Rd.,
RST Tel:
ail
131)183
0.75
B237
035
0C184
13(212
13('2(3
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01-677 2424 Telex: 946708 RST
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35.111
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MXI64
42.01
17.51
12.110
17.511
OA2
0A3
9.00
OA4
?.IMI
TD13-I0
7.511
1'D113-IIIF 35.00
11S
51.00
T121
37.51
PCL80.5/85
105(11)
1E.06-4110 45.(0
2.5(0
PFL2110
PL36
PL81
2.51
pLBIA
2.00
1.511
PL8112
6.141
PY33
2.50
PY81
"
5.5)
6.11)
6.10
IB35A
PY510A
PY810
4.01
1.50
U25
U26
PY8111
1.5(1
L137
01451
82.5)
48.30
OOV06-01A
46.00
00V07-5)76.65
00Z11640A
0.16
41.35
11.36
640211.3h
2C43
7(1.(X1
fi88
6BA6
6BA7
6BA8A
98.1X1
2170A
383.10
613C4
6131(6
21700
21(25
336.00
125.(0
66116
6BJ6
3410Z
115.10
6BK4
35(X1Z
1110.00
3A5
3B24
3828
3.10
11.01
20.00
VCR517('
1(1.110
SADPI
7411
55.4X1
7312
7413
30L17
2.0)
8.00
3.01
3.50
5.75
30134
2.50
2.51
3.00
607
6P225
4.1X)
607
3.75
61(7
3.25
61211118 61098
6SA7
150BA
3.(X)
)5(1B3
3.1X1
150C2
I50C4
4.011)
6557
2.75
723AB
4.01
61_15G
3,541
1.50
2.50
2.25
4.51
85.00
4.50
1)5.00
6118A
2.25
4.25
803
805
807
1.75
2.50
4.00
4.00
4.25
3.50
2.25
2.00
5.00
1.50
45.01
2.00
613X7GT
1.75
01341
O).fX)
6C4
11.48
7451)
n30
0.36
0.36
0.36
0.36
7451
(1.311
7453
7454
11.311
746)
030
11.48
0.36
0.36
7470
7472
7473
7474
7475
7476
11.36
41.36
0.30
030
0.yg
41.4f)
11.4?
11.36
74811
1132
036
74111
(I.36
7483
11.18
11.55
036
0..65
0.48
FOR FURTHER DETAILS
3.50
6.(0
6,00
1.50
5,00
2.75
1.25
3.0)
7Y4
7Z4
12AH8
I2AT6
I2AT7
I2AU6
I2AU7
2.5)
;4i6
iizi
0.72
0.36
0.54
749(1
7491
7492
7493
7494
7495
7496
7497
74100
741117
7411N
74110
74111
74116
74119
74119
(1.54
0.78
0.65
0.60
3.90
0.84
0.7
U.54
U.48
0.51
1.50
1.20
1.50
6I46A
235.0)
200.00
12.00
1201
6189
6201
19.10
9.50
11.40
6442
6550
20.00
8.00
688313
12.50
6973
7025
7.50
3.00
7027A
8.110
6.25
15.0)
7551
7586
7587
10.49
11.53
931A
1624
1625
2050
4212E
555IA
74I47
1.511
74148
74150
74154
74154
74156
74156
I1.40
74190
74191
74192
74193
74194
74195
74196
74197
74198
74199
11.61
11.48
609713
18045
18046
922
74181)
1.40
14110
6097A
16.50
2.50
6.00
11.53
11.46
0.J6
6.110
12.00
0.71)
1.61
3.75
10,25
11,75
6.00
8068
8136
8417
18042
74141
74143
74145
1.30
0.72
6163
6064
6067
813A
18.33
812A
35.00
813 valve 65.00
833A
193.16
866A
20.03
872A
20,00
0.54
0.55
0.61
12.34
6.00
23,00
56.00
6.01
74172
74173
74174
74175
74176
0.70
0.60
6058
6159
6161
7895
5544
5545
1.75
2.5(1
4.50
12.25
7868
421211
12AV6
2.25
6)57
760
1.75
2.50
5.00
3.25
6.00
35.00
125.00
25.00
2.50
3.50
45.00
3.75
2.50
6CB6A
6CD6GA
74122
74123
74125
74126
74128
74136
211
20.00
20,00
8,45
6.50
8.35
5.1X1
17.50
5965
6015
6121
61466
6459B
92AG
92AV
95AI
31.50
5876A5879
5886
5963
6.0(1
14.54
15.45
90CV
4.1X1
4.00
12.00
5842
6072
6081
3.51)
7B7
7C3
7C6
4.00
4.50
5814A
5840
4.51
7.50
6,45
20,01
20.00
90AG
90AV
90CG
6X5GT
5.50
6.015
85A1
85A2
6SL7GT
6SN7GT
6S07
6X4
731
11.37
7.05
2.50
75C1
651(7
6V6GT
1.811
4,45
4.50
28.00
6.00
4.50,
75B1
90C1
65R74.00
2.(10
3.00
1.80
1.00
1.50
10110
3,41
1.811
155.35
9,010
5)C4
65117
6517
3V4
4-65A
4-125A
1.25
30PL14
30PL15
35W4
3.25
3.25
1.50
5.00
3S4
11.48
311PLI
1,50
(917
3E29
7442
31119
3.00
2.50
4.50
2.10
7441
3005
3.00
2.75
2.51
3.10
3.25
6SC7
1.75
1.85
148
3.110
2.50
2.50
2.51
3.00
6N2P
6N3P
6BW6
6BW7
Terms of business; CWO. Postage and packing valves and semiconductors 50p per order. CRTs 1.511. Prices excluding VAT, add 15%.
Price ruling at time of despatch.
In some CaSCx prices of Mullard and USA valves will he higher than those advertised. Prices correct when going to press.
Account facilities available to approved companies with minimum order charge 111. Cartage and packing 1.511 on credit orders.
Over III,INNI types of valves, tubes and semiconductors in stock. Quotations for any types not listed. S.A.E.
86
3.(10
613S7
0.36
13
2.10
1.50
12.110
7432
7433
7437
7438
7439
CIRCLE
311FLI2
31111I4
3011
616GT
25.00
11.4K
1.61
1.61
1.38
3C24
3CX1111IA
7416
7417
7420
00
1741.(0
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2.010
3C23
6B26
65,141
12E1
13E1
31FLI2
2.25
2.501
2.511
12E14
3.00
3015
3.00
1.511
2.25
341C18
UBC41
UBF89
UCC84
UCC85
UFC80
UCI142
6BT8A
3.00
28,00
5,5()
8.93
4.75
7.50
2.75
3.01
13B41
47.0)
12EII71
3110
UAF4?
2.50
12.(0
2.75
12BY7
2.50
6J4
616
7R7
7S7
7430
113fi
1136
8,75
1.25
5.01
1213117
3.010
6116
7117
0.55
0.i6
66L6
6BL7GT
6BM6
8.66
2.50
2.110
2.111
6.0)
74117
74N
6AS6
6AS7G
6A1'6
2.5)
67.25
3,50
740,
7418
2A05
1.511
4.00
9.69
6.02
4.75
3.50
3.25
5642
5654
5651
5670
5675
5687
5696
5718
5725
5726
5727
5749
5751
5763
3(C15
3IC17
2,010
41.42
11.42
11.18
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5552A
1.75
4.01
3.51
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613R7
1176
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5.99
2.50
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6L6GC
6L6GT
6L7
5.0I
3.511
14.00
2.75
61307A
7404
61(136
61.6G
3,00
4.75
12B4A
12BA6
I?BE6
47.511
61306
74113
74115
6K7
6K8
4.25
3.01
1.511
I2AX7
I2AY7A
19115
15.35
20.05
17.51
17,50
7422
7423
7424
7427
7428
111P
3.411
3.1X1
6137
INTEGRATED CIRCUITS
740
740
61E6
8,10
1.6)
33.50
3829
3B24)84
36241M
11C118
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13,75
2.51)
617
1.75
1.75
1650.000
1.25
2.5(I
UABC811
38.011
25,01
3.51
2.51)
6-30L2
60.IX1
245.111
597,0D
5L4GT
I1.5
3.25
8.25
35.00
4.00
2.50
2ASI5
2C39A
1,75
1.75
1.75
56.0)
5140
5'Z3
6AU5GT
6AU6
6AVSGA
6AV6
6AX5GT
2155
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00V03- 0126.25
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3.011
25.110
48.0X1
64.110
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611319
6AM4
6AM5
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6AN5
6AN8A
1.M1042
113301'
1624
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6AK6
19.36
16.66
17.77
63.75
2.511
2.511
9.01
9.00
9.00
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ZM1041
13,011
6CL
6CW4
6D2
601(6
600613
4EA8
6EB8
6EW6
616
2.50
8.110
9.111
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2,51)
6C116
0
1
1.M10111
25,01
6CG7
87.00
6123
6128
6133
6A116
OAKS
ZMI0211
ZMI0211
ZM1022
8(1.00
211.00
1211.00
58.1X1
5,50
25.1X1
1'Y7 -60110A
U18.211
'
Z803U
Z259
2E26
2J4Z
579,(1)
5B25M
XRI-64141151100
YD1120 395.00
YDI2411 490.I10
XRI-3211IA
1'Y6511X1W
446.01
'l'Y7[,1110W
4CX250B
4CX350A
4X151A
4X15110
6AB4
6AB7
6AC7
6AF4A
6AG7
395.1102021
TL41
3WPI
10.00
TY6-5IMNIB
53.75
II(1.110
236.0)
'IY6-800 231301
''Y66-50010A
1.51
1.51
1.25
74111
6'1I
XRI-320I
440IA
5Y3GT
185.111
XRI-1601IA
1S5
1'1'4
54.00
30.(0
X02-641)
IRS
2.00
111.1X1
8.00'
37.5(1
-6).010
78.75
100.111
X05-5111
11550
PY88
O0V02-6
35.0I
XGI-2500
1B63
py83
7401
12_.511
111,141
UY81
VL5631.
88.211
1'Y4-400
'I-Y4-500
'1'Y5-500
pY82
VCR.517B
VCR138A
1500VCR139A
1Y2-125
2.511
35,141
141.1M1
'I11110
55.00
76,01
Prices on
113.12
12.00
1972
1.75
PLOW
3111
3112
S1P7
31(11
3RP1
2.50
2.50
6.10
4.50
63.32
65.00
56.83
3.141
6.341
application
0113 -SI
D117 -I
VCR138
P(I8(3
PCL84
PCL85
PCl-86
6.00
CRT sockets
5,(0
SU41
SU42
14.(13,
25311
EC sockets
'Texas
low profile
8 pin
14 pin
16 pin
SI'V28(L8021.(41
1.70
73E
PL519
4(1.IMI
15.11)
58117
58.(17
1.70
2.5()
7115
5U P7
DG7-5
411.111
1.70
2.51)
11.37
SCPIA
5PI5A
007-31
007-32
007-36
RR3-2511
RR3-12501 45.75
6534I
SIIEI2
6.00
SERI
6.(41
SI3OP
Sl'V28(1-40 14,01
PL5(I4
pL5(X4
PL. 09
25.52
147.10
51(1()
15.0)
3,25
2.51
6.10
6.I0
3.40
3.01
9.24
2.50
59.50
RG3-251A 32.68
RG3-1250 59.01
RG4-1250 61.61
RG4-3000 99.45
1.50
pCL82
566.80
46.00
R18
R19
R20
RG3-1250
2.50
2.10
3.25
3.25
1.511
5(,,7(1
N78
1,75
2.00
2.50
17.25
131.25
152.25
21115
MXI68
OZ06-211
R
R17
2.50
1.6)
1.60
2.00
2.00
PCF805
2018.110
0Y5 -3000A
2.00
2.511
MX152
MX161
9.111
0Y5-510
1.511
pL84
MX145
MXI6,
0Y3-65
0Y3-(25
0Y4-250
1.50
pL113
115.0)
MXI51
0Y4-4110
PL82
14
MXI23
1.75
1.75
1.75
S.(Ml
7.50
MXII9
PCC84
PCC85
PCC88
PCC89
PCC189
PCC805
PC(1816
PCE82
P('F80)
PC182
K1146
PC187
PC1200
PC1201
PCENO
PCFB(R
V08-)(XI
8.25
M82?4
1.50
1.50
331)
3.50
3.50
p('97
V(4-7
2.50
2.50
3.50
2.50
2.50
11.75
175
9.01
GN4A
GN4A
6.51)
1.75
MU
01,3711
G55IK
12.25
3.00
1.75
1.75
EZ91
1175
10.85
2.511
11.81
8.15
8,01
10.30
7.511
2.50
PC'88
PC95
1C18115
6,00
EZ41
OZ4
1086
PCFtBM(
810
M9144
M8149
M8161
M8162
M8163
EZJII
003
111.43
6.181
018140
M8141
M81-12
EYW)?
EZ35
0(3
10.25
M8198
M8199
M8100
M8136
M8137
M8225
M8248
MD2901
1W4-5410
1W4-8111
EC! -85
8.41
8,25
'/.8?
9.69
MN195
M8196
M8204
M8212
M8223
9.24
EMU
8.111
12.34
M81911
2.511
2.511
1.50
1.50
1.75
13.27
815
EL8?2
1.75
3.51
3.00
2,51
2.51
1,51
8.?5
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I0.110
EL%21
3.00
E.C1183
1.86C
E.88C
1.88C
310
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ECM
2.00EC9135
E82CC
183CC
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1.511
EXICC
EXIL
M8I197
E('C'8117
EC1142
1('1181
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M8496
2.75
2.50
4.75
1.50
110I1'
M8083
8.511
E0485
EMK7
DM 1611
DY87
E81('F
7.35
8.93
2.10
ECF82
KTW63
M8079
31110
EC'C11
12.5(1
2.X1
DOC('
EOM
8.110
EC'C489
2.50
2.50
K'1W6?
2.00MK091
ELI56
EM34
EMWI
EM81
EM84
2.50
3.50
Lion
12.00
KT88Gold
Lion
241.01
KI'W61
2.511
2.75
3.25
2.I0
ECC88
5110
K1770o1d
M81180
M811XI
M81182
E('('89
EC'C'86
DLS19
DM71)
DM71
DY8112
E55L
1.75
1.75
1.75
1.75
1.75
2.50
2.80
2.51
18.50
5.25
6.01
2.25
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4.14)
4.50
5,50
4110
4.75
4.00.
1.50
1,75
4,511
GZ34
EI33
EL34MLI1
1.25
462.00
0Z33
15.111
4.95
1.51)
EC92
EC175
ECC33
ECC35
ECC41
E('C'81
ECC82
EC'C83
1211)
401
(303
OC2
400PC1X)
1510
EBflB)
1.75
1.75
3.111
K'166
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18.7(1
G -L32
0Z37
K'l'fil
EBC'KI
EC)I
2.101
211.(10
1.50
354.811
129.911
22.01
22.10
25.00
GXU51
0Y501
1.75
349.15
C:3A
25.40
44.50
0XU4
2.01
2.00
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20.I0
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2.50-
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1,50
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200
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C'L33
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01.94
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2.51)
11341
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5.94)
E18(14S
E11815S
EAflf(II
185.110
44.115
2.511
3.51
61.01
5895
11119
1.50
1.25
58.11)
DL92
EP3
EAC9I
EAF4?
S810
10(96UK
17.511
35.48
32.25
2,51
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13501
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0X132
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8.91
22.51
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DE'124
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2111M1
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15.1X1
DA41
DA42
DAF91
25.011
211.00
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17.511
25.111
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2_.95
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B'1215
C'BL 31
16,00
GI'IC'
2,511
11861
A252I
0'117
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3.50
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13'15
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13.25
9.01
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35.(0
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12.05EF86
13,50
A1834
A2087
A2134
A2293
A2426
AZ31
10.51
6.00
18.51
4110
3.50
7.50
Tested
Ex -Equipment
300.00
300.00
110.10
4CX250B8.50
CV Devices
150010
120.00
Pnceson
application
72f
4.0)
0.72
0.60
1.00
1.00
1,48
1.20
1.20
1.10)
0.61
1.10
(1.72
1,00
1.00
2.20
2.20
Large stocks
TAA630S
TAA701
TBA4800
TBA52110
TBA530
TBA5500
TBA560
TBA673
TBA700
TBA7010
TBA75(g
1.50
1.50
1,50
1.75
1.75
1,75
1.50
1.75
1,50
TBA801
TBA920
1.110
TCA27(10
TCA761A
I'
TBA990
Telephone 01-677 2424/7

Telex 946708
E. & O.E.
Open to callers MondayMonda Frida 9 a.m.-5
iis
3.01
Fridayp m.
WW
1.75
1,50
1.00
[NEW PRODUCTS
Telephone -radio
interface
Hand portable radios

The Landmaster III from Pace
Communications is supplied with
one channel already crystalled, a
flexible aerial, 500mAh battery and a
trickle charger. V.h.f. and u.h.f.
models are available. Manufactured
in Japan, the sets are claimed to be
designed and constructed to a high
specification and yet remain
competitively priced.
A telephone and radio inconnect

system, the 27A300 Phone -patch
from Racal Acoustics, connects a
simplex radio set with the public
telephone network. The instrument
can monitor the radio and telephone
lines and can link them. If either line
offers poor reception the operator
can manually dial the radio.
Automatic keying of the radio is
achieved by a voice operated switch.
Racal cite search and rescue
operations as being a specially useful
application where radios at the scene
of an accident can access the public
telephone system, giving a greater
range.
Professional c.b.
radio
Telecomms claim to market the only
934MHz citizens' band tranceivers
available in the UK. The Nevada
range of equipment includes
transceivers and all related
equipment. Several transceivers
have been purchased by BT for
communications at the Goonhilly
satellite station.
Telecomms also have a wide-band
aerial for use with cellular radio. The
855 to 955MHz beam aerial can be
used to access cellular radio from
areas that are not within the cells.
Satellite receiver front end

Where the smallest antennae are
desired, the FB -1 range of low -noise
block -converters (1.n.bs) can be used
to receive satellite tv signals. The
1.n.b. is positioned at the focal point
of a dish antenna and can collect,
convert and amplify the satellite
signal. Particular care has been taken
over the tuning of the gas-fet stages
to offer greatly improved
performance over previously
available systems, with noise figures

as low as 1.8dB at 20C and a
guaranteed noise level of <2.1dB
over the entire frequency band and
temperature ranges covered. Special
versions, for data communications,
offer highly stable oscillator circuits
with phase noise eliminated.
Available through Space
Communications (Sat -Tel) Ltd.
262 on reply card
Plug in panels for Storno two-way

radio equipment offer c.t.c.s.s.
encoding and decoding. With the
CTL Radiocom panels installed, the
radio has the added facilities of p.t.t.
phone
A single -channel mobile radio, the
UKV62 from Communique (UK), is
designed and made in the UK. At
presenmt it is available in the v.h.f.
160 to 175MHz band but a u.h.f. 420
to 470MHz version will be available
soon. Various signalling options are
available including c.t.c.s.s.
encoding and lockout, selcall and
base -station adaptors enable the set
to be integrated into new or existing
systems.
are fully synthesized in the Sealine

MC -56 hand-held v.h.f.
selectable between 1 and 3W.

Marconi test set
timer, hookswitch monitor, busy

lockout, with or without a warning
tone and p.t.t. duration limiter. All
the additional options can be
defeated by links, operated from a
Low cost radio-
All 55 international marine channels
radiotelephone from Shipmate. Also

included is the UK Marina channel.
The Coastguard channel '0' can be
added for authorized user and
Channel 16 can be selected instantly
by push-button. The set includes a
dual -watch facility and comes with a
battery charger. The output power is
Encoders for mobile

radio
rocker switch assembly thus

enabling the host radio to be applied
to many varying system parameters.
...and at sea
Radio test sets

Two instruments from Farnell make
testing easier. The PTS1000 is a
portable transmitter test set that
operates from a battery pack, a
vehicle battery or a.c. main power. It
has an operating frequency up to
1GHz. It integrates all the
instruments normally required to

check the performance of a
transmitter up to 100W continuous
rating: r.f. counter, modulation
meter, r.f. and a.f. power meter, a.f.
voltmeter, distortion analyser,
weighing filters and r.f. power load.
It can also measure aerial efficiency
using an optional remote directional
power head. Combined with a signal
generator the set can be used as
complete transceiver test set with

only four connections to the device
under test. This facility adds
frequency, distortion and sensitivity
measurement of a receiver.
Another set for communications
testing is the CTS520, designed for
the service or production testing of
simplex or duplex radio transceivers.
This adds synthsized r.f. and a.f.
signal generators, a sinad meter and
a c.t.c.s.s. tone generator to the
facilities incorporated in the other
instument. The synthesized signal
generator offers the benefits of drift free measurement, absolute setting
accuracy, low r.f. leakage and direct
offset frequency measurements.
Designed for bench and field work,

the Marconi 2955 radio
communications test set can test all
types of amplitude, frequencyand
phase -modulated mobile radio
equipment. Applications include
low -power hand portables and
mobiles using selective calling, full
duplex radio telephones, base
stations and repeater equipment.
Facilities include r.f. and a.f. signal
generators, r.f. frequency and power
meters, modulation, sinad and s/n
meters and an a.f. frequency meter.
The integral digital storage
oscilloscope offers single or
repetitive sweep in transmitter,
receiver and audio test modes,
calibrated for a.m. f.m. and p.m.
Selcall encoder/decoder facilities are
available as is a GPIB interface. Buy
from Electronic Brokers, 212 on the
reply card, or hire from Electroplan
Hire, 213 on the reply card.

87
from
the highest quality
the most competitive prices
Hitachi OsciIloscopes
139h5
299
+VAT
lituclu Oscilloscopes prusidc the t(ualit\ and pertunnance that srni',I

espect train such a tanutus name. \\ lilt a nests -estended 14 model 1.111/c
that represents t11/ hest salue lot runes sailable an\sshere.
Q.
\ -6sO
V-212/222 20MHz Dual Trace

20MHz Sweep Dela\
V-223
(illustrated)
20111-1i Alini-Pututble
\ -209
\-42_2
\ -423
ra
1O\1 Hi Dual
4011Hi Sssecp Drl:n
5011Hi
-5(19
61111H Dual
\ 1100
\-134
I(K)\111i D11\1 Counter
II0MH/ Iuhe sIiiiage

Ill \I Hi I)iciial 'si iii ace
40MHi Digital titolage
\C-(,(11>
\ C-(,141
\lini -Portable
inthtsc
111111111
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Quad I lace
IOIIMHi Tour (hamlet
-1(h11
Prices start at .290 plus vat (20MHz dual trace) including a 2yr. warranty.
1'te hold the range in stock for immediate deliser
I
-or colour brochure en ing speed icatlons and pitres riot, (0480) 63570
St. Ices, Cambs. PEI 74BG
thurlbs Electronics Ltd, New Road,

IEEE -488 controlled laboratory Power Supplies -at low cost

the new Thurlby PL- GP series
30V/2A and 15V/4A single and twin units
Constant voltage or constant current operation
Programmable to 10mV and 10mA resolution
Readback of current demand via the bus
Twin units have fully independent outputs
Remote sensing terminals provided

Bench mounting or 19" rack mounting
Singles 395 + vat, Twin units 598 + vat
Thurlby Electronics Ltd
New Road, St. Ives, Cambs. PE17 4BG
Tel: (04801 63570
III
Thurlbyjp
designed and built in Britain
The world's most advanced low-cost bench multimeter!

Thurlby 1905a 349+ VAT
A complete high performance bench DMM
nA.
0V, 1m f2
5 1/2 digits; 0.015% acc;
Full ac and current functions as standard
A sophisticated computing and logging DMM
Linear scaling with offset; null/relative
Percentage deviation; running average
dBV, dBm general logarithmic calculations
Limits comparison; min and max storage
100 reading timed data logging
RS232 and IEEE -488 interface options
1

New Rudd, Si Ises Cambs. PE17 4BG
CHICLE
33 FOR
Tel: (0480) 63570

FURTHER DETAILS
III
Now Thurlby makes logic analysis affordable !

the new Thurlby LA -160
channels, expands to 32
Clock rates up to 20MHz
State and timing displays
Selectable display formats
16
Thurlby/
from
395+vat
2K word acquisition memory

Non-volatile reference memory
Search and compare facilities
Hard -copy data print -ou'
An oscilloscope and logic probe are not enough to unravel the complexities
of today's electronic equipment. A logic analyser is as essential for
observing digital signals as an oscilloscope is for observing analogue
signals, and now Thurlby puts one within every engineer's reach.
Contact us now and get the full technical data.
III Thurlby/

New Road, St.lves, Huntingdon,
Cambs. PE17 4BG, England. Tel:
104801
63570
flNEW PRODUCTS
Graphics design kit
BBC or IBM control
A complete
system
package provides a
comprehensive full -colour bitmapped graphics capability. Six
chips comprise the kit which can be
interfaced with almost any
microprocessor to provide screen
resolutions from 256 to 256 pixels up
to 4096 by 4096. The Texas
TMS34061 video system controller
eliminates the need for separate text
and graphics systems. A video palette
offers almost unlimited colours and
the kit is completed by two 64K by 4
video rams two 4 -bit shift registers
and a 68 -pin socket for the
controller. Full documentation,
application notes and data are
provided. We have had identical
notices of the kit from two sources;
VSI and Online.
Miniature d.c.
converters
5,12 and 15V versions of the Newport
d.c./d.c. converters are as small as
integrated circuits. NM0505i, 1212i
and 1515i produce their respective
voltages (plus and minus) at 750W
from a 5N/supply. Input -to -output
isolation is 500V. With high
efficiency and a wide operating
temperature range, the modules can
be used at points of load on p.c.bs,
elminating complex power bus

tracks.
A Eurocard -based control
system for
laboratory or factory is produced by
Paul Fray. The system is designed to
run with Spider, the real-time
software package that uses BBC Basic
to program complex control
sequences. A five -card rack connects
to the BBC 1MHz bus through an
expansion card. Alternatively a 6502
processor card running BBC Basic
and Spider software can be
connected with up to nine interface
or memory cards and built-in disc
drives. This system is self contained
but can be programmed through its
serial port by a terminal, either a
BBC or an IBM PC. The 5 -card
version can also be used with the
terminal's discs and printer used for
recording/storage of data.Spider is
now available as a plug-in rom
cartridge for the BBC Master.
ECL/TTL logic arrays

Different logic families; e.c.l. or t.t.l.
or both can be combined on a single
chip with the AMCC Q3500 series of
logic arrays. Three devices have the
equivalents of 1300, 2400 and 3500
gates and support respectively 76, 98
and 120 input/output pins with a
typical gate delay of 0.275ns. The
arrays use 3 -level series gating
techniques to provide both density
and speed improvements.
The QM1600 series can provide up

to 1600 equivalent gates in e.c.I.
coupled to 1280bit of e.c.l. ram
which maybe organized to any bit,
byte or word configuration. Suitable
design software for modelling and
testing the devices runs on most
c.a.e. workstations. Exclusive
distribution is handled by Hi -Tek
Electronics.
Single -chip data

system
transformers
Designed and made in the UK, these
toroidal transformers come in a
range of five power ratings from 15 to
130VA, 48 to 60Hz. Maximum
ambient temperature is 55C.

Intended for applications requiring
low magnetic field and low
temperature rise, the transformers
incorporate a copper screen between
primary and secondary windings.
High efficiency ratio with low weight
and small size make them useful in
many applications.
PAGE 83
An analogue -to-digital peripheral i.c.

is claimed by Texas Instruments to be
a complete data aquisition system on
32 -bits and 12.5

mips
single chip. It includes an internal

systems clock, sample -and -hold, 8 bit a -to -d converter, data register and
control logic. It is designed as a serial
interface for a processor or
peripheral through a three-state data
output and an analogue input. The
on -chip systems clock operates
typically at 4MHz and allows the
device to work independently of
serial input/output data timing. Used
in conjunction with the i/o clock this
allows high-speed data transfer and
sample rates of 40 000 cycles/s.
Suggested applications include

engine and machinery analysis,
remote sensing, analogue -to-digital
controls such as joysticks in
computer applications, and in
battery -operated portable
instruments. The conversion
accuracy is 0.5 of the 1.s.b. in less
than 19s, while power
consumption of the c-mos device is
typically 6mW.
Toroidal
Switch -mode control chip

Switch -mode power supplies with
increased efficiency and simplified
design are made possible by Rifa's
new control circuits; RL3525 for
voltage mode and RL3846 for current
mode. All functions of a highperformance controller are
integrated, needing only a small
number of external components to
complete the supply. Included are

dual totem -pole outputs with high
drive capability, soft start, under voltage control, p.w.m. and voltage
references. Wide operating voltage
range and high switching frequency
range increase the areas of
application.
Motorola's 25MHz version of the

MC68020 32 -bit processor and the
20MHz version of the MC68881
Floating-point co -processor have
been produced. The new processor
can operate in bursts of 12.5million
instructions/s buta more realistic
figure is a sustained throughput of
5mips; seven times as fast as the
16 -bit 68000. It owes its speed to the
on -chip cache instruction memory,
the three -stage instruction pipeline,
the instruction set and the
addressing modes. It is constructed
in high-speed c-mos with 1.5micron
geometry. The maths co-processor
offers ove 40 floating point functions.
It handles full extended precision
(80 -bit) for trigonometry,
hyperbolics, logarithms, square
roots etc. all in hardware. The coprocessor works concurrently with
the c.p.u. and is transparent to the
systems programmer.
89
01-208 1177
TECHNOMATIC
5.25" Single Drives 40/50 switchable:

TS400 400K/640K
PS400 400K/640K with integral mains power supply
5.25" Dual Drives 40/80 switchable:
TD800 800K/1280K
P0800 800K/1280K with integral mains power supply
PD800P 800K/1280K with integral mains power supply and monitor stand
3.5" 80T DS Drives:
TS351 Single 400K/640K
PS351 Single 400K/640K with integral mains power supply
TD352 Dual 800K/1280K
PD352 Dual 800K/1280K with integral mains power supply
395 (a)
319 (a)
BBC MASTER Foundation computer 128K

BBC MASTER Econet computer 128K (only ANFS)
Turbo (65C -02) Expansion Module
105 (b)
43 (c)
ADF13
Rom Cartridge
13 (b)
ADF10
Econet Module
Ref. Manual Part II
ADJ22
Ref. Manual Part 1
14.95 (c)
ADJ23
14.95 (c)
19.50 (c)
ADJ24
Advanced Ref. Manual
BBC MASTER COMPACT
A free packet of ten 3.5" DS discs with each Compact
SYSTEM 1 128K, Single 640K Drive and oundled software 385 (a)
SYSTEM 2 System 1 with a 12" Hi Res Mono Monitor 469 (a)
SYSTEM 3 System 1 with a 14" Med Res RGB Monitor 599 (a)
Second Drive Kit 99 (c) Extension Cable for ext. 5.25" drive 10 (d)
View 3.0 User Guide 10 (d)
Viewsheet User Guide 10 (d)
BBC Dust Cover 4.50 (d)
1770 DFS Upgrade for Model B 43.50 (d)
ADFS ROM (for B with 1770 DFS & B Plus) 26 (d)
64K Upgrade Kit for B plus 35 (d)
ACORN Z80 2nd Processors 329 (a)
ACORN 6502 2nd Processor 179 (b)
MULTIFORM Z80 2nd Processor 299 (b)
ACORN IEEE Interface 2,69 (a)
TORCH Z80 2nd Processor ZEP 100
229 (a)
TZDP 240: ZEP 100 with Technomatic PDBOOP dual drive with built-in monitor stand
439 (a)
51/4"
40 T SS DD
80 T SS DD
L0800 (80 col)

L01000 (136 col)
TAXAN:
KP810 (80 col)
KP910 (156 col)
219 (a)
389 (a)
JUKI
6100 (daisy wheel)
249 (a)
299 (a)
420 (a)
525 (a)
409 (a)
Integres Jet Printer

Canon PJ1080A
1431 AP Std Res

1451 AP Std Res
Epson versions for FX/RX, MX

28 (d)
(A3 Plotter)
wide range of printer attachments (sheet feeders, tractor feeds etc)

in stock. Serial, parallel, IEEE and other interfaces also available. Ribbons
available for all above plotters. Pens with a variety of tips and colours also
available. Please phone for details and prices.
a
Plain Fanfold Paper with extra fine perforation (Clean Edge):

2000 sheets 9.5' x 11' 13(b) 2000 sheets 14.5' X 11" 18.50(b)
Labels per 1000s: Single Row 3:, x 7/16" 5.25(d) Triple Row 2-7/16"
1
7/16' 5.00(d)
WS 3000 RANGE the new professional series. All are intelligent and 'Hayes'
compatible, allowing simply 'English' commands to control its many features. All models
feature Auto -Dial with 10 number memory, Auto -Answer, Speed buttering, printer port,
data security option etc. All models are factory upgradeable.
1223- An economically
priced BABT approved modem complying with
CCITT V23 standard capable of operating at
1200/75bps and 75/1200bps and 1200/1200bps
pseudo full duplex. It is line powered, does not
require external power source. It is supplied
with software suitable for connecting to
PRESTEL, Micronet 800, Telecom Gold and a
host of bulieting boards. Special Offer 49 (b).
GEC DATACHAT
SOFTY
II
This low cost intelligent eprom programmer can program 2716, 2516.
2532, 2732. and with an adaptor, 2564 and 2764. Displays 512 byte
page
on
TV
has
a
serial
and
parallel I/O routines. Can be used as an emulator, cassette interlace.
Softy II
195.00(b)
Adaptor
for
2764/
2564..
25.00
2764-25 2:00(d1;
27128-25 2:50(d);
6264 LP -15 3:40(d);
HANTAREX HX12
69
PRINTER BUFFER
The buffer offers a storage of 64K. Data from three
computers can be loaded into the buffer which will
continue accepting data until it is full. The buffer
will automatically switch from one computer to
next as soon as that computer has dumped all its
data. The computer then is available for other uses.
LED bar-graph indicates memory usage. Simple
push button control provides REPEAT, PAUSE and
RESET functions. Integral power supply. 199 (b).
With 256K 275 (b).
BBC Cable Set 30.
Serial Test Cable
Serial Mini Patch Box
Serial Mini Test
Serial Cable switchable at both ends

allowing pin options to be re-routed or
linked at either end
making it possible
to produce almost any cable
configuration on site.
Available as M/M or M/F
24.75 (d)
Allows an easy method to

reconfigure pin functions
without rewiring the cable
assay. Jumpers can be used
and reused.
22 (d)
Monitors RS232C and CCITT

V24 Transmissions,
indicating status with dual
colour LEDs on 7 most
significant lines. Connects in
22.50 (d)
Line.
EDGE
I.D. CONNECTORS
No of
ways
Header Recep.
Plug
'ac le
90p
145p
175p
200p
220p
235p
10
20
26
34
40
50
Edge
Conn.
1209
195p
240p
3209
340p
390p
8Sp
125p
150p
160p
190p
200p
CONNECTORS
No of Ways
9
15
25
37
MALE:
Ang Pins 120 180 230 350
Solder
IDC
60 85 125
175 275 325
170
FEMALE:
St Pin
100 140 210 380

Ang Pins 160 210 275 440
Solder
90 130 195 290
IDC
195 325 375
St Hood
90 95 100 120
130 150 175
Screw
Lock
TEXTOOL ZIF
SOCKETS
28-0169.10
24 -pin C7.50
40.910012:10
AMPHENOL
CONNECTORS
CONNECTORS
(Spoodblock Type)
--
---
EURO CONNECTORS
DIN 41612
2 X 32 way St Pin
2x32 way Ang Pin
3 x 32 way St Pin
3X32 way Ang Pin
IDC Skt A + B
IDC Skt A + C
Plug
Skt
230p 275p
275p 320p
260p 300p
375p 400p
400p
400p
For 2 x 32 way please specify

spacing (A + B, A + C).
MISC CONNS
21 pin Snarl Connector
8 pin Video Connector
RIBBON CABLE
,grey/metre)
36 way plug Centronics
0.1. 0.156'
2 x 6 -way (commodore)
300p
2 x 10 -way
150p
350p
2 x 12 -way Iwc 201
140p
2 x 18 -way
175p
220p
2 x 23-way IZx811
225p
220p
2 x 25-way
2x 28 -way ISpeclruml 200p
2 x 36-way
2s0p
43
x
-way
260p
2 x 22 -way
190p
2 x 43.way
395p
x77way
400p
500-p
2 x 50.way1S100conn,
600p
TECHNOLINE VIEWDATA SYSTEM. TEL: 01-450 9764

90
75
79
CONNECTOR SYSTEMS
SPECIAL OFFER
PHILIPS 12" Hl -RES

BM7502 green screen
BM7522 amber screen
UVERASERS
UV1T Eraser with built-in timer and mains indicator.
Built:in safety interlock to avoid accidental exposure
to the harmful UV rays.
It can handle up to 5 eproms at a time with an average
erasing time of about 20 mins. 59 + 2 p&p.
UV1 as above but without the timer. 47 + 2 p&p.
For Industrial Users, we offer UV140 & UV141 erasers with handling capacity of 14 eproms. UV141 has
a built in timer. Both offer full built in safety features
UV140 69, UV141 85, p&p 2.50.
MODEMS
GEC Data Cable for WS3000 7 (d). Data Cables for

other micros available. The WS3000 range all have BT
approval.
27.00 (d)
ACCESSORIES
Microvitec Swivel Base
20
Taxan Mono Swivel Base with
clock
22
Philips Swivel Base
14
BBC RGB Cable
5
Microvitec
3.50
Taxan 5 (d)
Monochrome 3.50
Touchtec - 501
255
MITSUBISHI
XC1404 14" Med Res RGB. IBM & BBC
229 (a)
compatible
MIRACLE WS 2000 - The world standard BT approved modem covering all standard
CCITT and BELL (outside UK only) standards up to 1200 baud. Allows communication
with virtually any computer system in the world. Expandability to Auto Dial and Auto
Answer with full software control enhance the considerable features already provided on
the modem. Mains powered. WS 2000 102 (c), Data Cable 7 (d), Auto Dial Card 26
(d), Auto Answer Card 26 (d).
WS3000 V21/23 (V21 & V23 + Bell 295 (a). WS3000

V22 (as above plus 1200 baud full duplex 495 (a).
WS3000 V22bis (as above plus 2400 baud full duplex)
650 (b).
WS3022 provides 1200/1200 baud full duplex operation.
395 (b).
WS3024 provides 2400/2400 baud fd only. 570 (b).
DISCS
20.00 (d)
90
98
195 (a)
260 (a)
TAXAN SUPERVISION II
12"- Hi Res with amber/green options.
IBM compatible
279 (a)
Taxan Supervision Ill
329 (a)
609 (a)
PRINTER ACCESSORIES
We hold
80 T SS DD
80 T DS DD
MONOCHROME
TAXAN 12" HI-RES
KX1201 G green screen
KX1203A amber screen
All above monitors available in plastic

or metal case.
325 (a)
464 (a)
Epson HI -80 (A4)

Hitachi 672 (A3)
179 (a)
225 (a)
365 (a)
MICROVITEC 14" RGB/PAL/Audio
Dotprint Plus NILO Rom for

and GLP
12.75 (d)
16.50 (d)
MONITORS
RGB 14"
1431 Std Res
1451 Med Res
1441 Hi Res
Graphics Workstation
159 (a)
KX P1080 (80 col)
31/2"
40 T DS DD
80 T DS DD
DRIVE ACCESSORIES
Single Disc Cable 6 (d)
Dual Disc Cable 8.50 (d)
10 Disc Library Casae 1.80 (d)
30 x 51/2 Disc Storage Box 6 (c)
50 x 51/2" Disc Lockable Box 9.50 (c)
100 x 51/2 Disc Lockable Box 13 (c)
PLOTTERS
NATIONAL PANASONIC
DISCS
10.50 (d)
16.50 (d)
239 (a)
279 (a)
COL OUR PRINTERS

Epson JX80
170 (b)
187 (b)
FLOPPICLENE Disc Head Cleaning Kit with 28 disposable cleaning discs

ensures continued optimum performance of the drives. 51/4" 12.50 (d)
31/2" 14.00 (d)
BROTHER
HR15 (Daisy Wheel)
99 (b)
119 (b)
FLOPPICLENE DRIVEHEAD CLEANING KIT
PRINTERS & PLOTTERS

STAR NL10 (Parallel Interface)
STAR NL10 (Serial Interface)
226 (a)
245 (a)
263 (a)
3M FLOPPY DISCS
We stock the full range of ACORN hardware and firmware and a very wide
range of other peripherals for the BBC. For detailed specifications and pricing
please send for our leaflet.
229 (a)
20 (c)
49 (c)
315 (a)
449 (a)
459 (a)
659 (a)
114 (b)
129 (b)
Industry Standard floppy discs with a lifetime guarantee Discs in packs of 10.
META Version III - The only package available in the micro market that will assemble 27
different processors at the price offered. Supplied on two 16K roms and two discs and
fully compatible with all BBC models. Please phone for comprehensive leaflet 145 (b).
EPSON
EPSON LX -86
Optional Tractor Feed LX80/86
Sheet FeederLX80/86
FX85 (80 col)
FX105 (136 col)
01-208 1177
DISC DRIVES
BBC Computer & Econet Referral Centre

AMB15
AMB12
AMC06
LTD
200p
200p
10 -way
(solder 500p (IDC) 475p

36 way skt Centronics
(solder) 550p (IDC) 500p
16 -way
20 -way
26 -way
24 way plug IEEE (solder)
475p (IDC) 475p

24 way skt IEEE (solderi
500p (IDC) 500p
PCB Mtg Skt Ang Pin
24 way 700p 36 way 750p
14
16
18
20
24
10
10
10
RS 232 JUMPERS
24"
24"
24"
24"
24"
way 01
Single end Male
Single end Female
Female Female
Mate Male
Male Female
125
DIL SWITCHES
4 -way
8 -way
90p
120p
6 -way
10 -way
34 -way
40 -way
5.00
5.25
10.00
9.50
9.50
105p
150p
28
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pin
pin
pin
pin
pin
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100p
110p
6p
75p
100p
160p
200p
150p
200p
225p
ATTENTION
All -prices in this double page
advertisment are subject to
change without notice.

ALL PRICES EXCLUDE VAT
Please add carriage 50p
unless indicated as follows:
(a) 8 (b) 2.50 (c) 1.50 (d)
1.00
Using 'Prestel' type protocols. For information

and orders 24 hour service, 7 days a week
160p
180p
200p
280p
50 -way
64 -way
DIL HEADERS
GENDER CHANGERS
25 way D type
Male to Male
Male to Female ...
Female to Female ..
40p
60p
65p
120p
74 SERIES
7400
7401
7402
7403
7404
7405
7406
7407
7408
7409
7410
7411
7412
7413
7414
7416
7417
7420
7421
7422
7423
7425
7426
7427
7428
7430
7432
7433
7437
7438
7439
7440
7441
7442A
7443A
7444
7445
7446A
7447A
7448
7450
7451
7453
7454
7460
7470
7472
7473
7474
7475
7476
7480
7481
7483A
7484A
7485
7486
7489
7490A
7491
7492A
7493A
7494
7495A
7496
7497
74100
74107
74109
74110
74111
74116
74118
74119
74120
74121
74122
74123
74125
74126
74128
74132
74136
74141
74142
74143
74144
74145
74147
74148
74150
74151 A
74153
74154
74155
74156
74157
74159
74160
74161
74162
74163
74164
74165
74166
74167
74170
74172
74173
74174
74175
74176
74178
74179
74180
74181
74182
74184
74185A
74190
74191
74192
74193
74194
74195
74196
74197
74198
74199
74221
74251
74259
74265
74273
74276
74278
74279
74283
74742
74290
74293
74298
74351
2.00
1.40
1.70
0.90
1.05
3.20
0.90
0.90
1.80
2.00
74365A 0.80
74366A 0.80
743676 0.80
74376
1.60
74390
1.10
74393
1.20
74490
1.40
74LS SERIES
74L00 0.24
74LS01 0.24
74LS02 0.24
74LS03 0.24
74LSO4 0.24
74LS05 0.24
74LS08 0.24
74LS09 0.24
74LS10 0.24
74LS11
0.24
74LS13 0.34
74LS14 0.50
74L15 0.24
74LS20 0.24
74LS21 0.24
74LS22 0.24
74LS24 0.50
74LS26 0.26
74LS27 0.24
741528 0.24
74LS30 0.24
74LS32 0.24
74LS32 0.24
74L33 0.24
741_537 0.24
741838 0.24
741540 0.24
741S42 0.50
74LS43 1.50
741548 0.90
74LS49 1.00
741551 0.24
741554 0.24
741555 0.24
74L573A 0.30
74LS74A 0.35
74L575 0.45
741S766 0.38
741578 0.42
74LS83A 0.70
74L585 0.75
74L586 0.35
741590 0.48
741591 0.90
741592 0.35
74LS93 0.54
7415958 0.75
741596 0.90
7415107 0.40
7415109 0.40
7415112 0.45
74L5113 0.45
74L5114 0.45
74L5122 0.70
7415123 0.80
74L5125 0.50
74L5126 0.50
7415132 0.65
74L5133 0.55
7415136 0.45
7415138 0.55
741S139 0.55
7415145 0.95
7415147 1.75
7415148 1.40
74L5151 0.85
74LS152 2.00
74LS153 0.85
74LS154 1.60
74LS155 0.65
74LS156 0.85
7415157 0.50
74L5158 0.65
74151606 0.85
74LS161A
74LS162A
74LS163A
0.75
0.75
0.75
74LS164 0.75
74151656
7415168A
1.10
1.50
7415168 1.30
7415169 1.00
7415170 1.40
74LS173A 1.00
7415174
7415175
74L5181
7415183
74L5190
7415191
7415192
0.75
0.75
2.00
1.90
0.75
0.75
0.80
74LS194A 0.75
741.S195A 0.75
7415196
74L197
7415221
7415240
7415241
74LS242
7415243
74LS244
7415245
74LS247
74L5248
74LS249
7415251
74LS253
74LS256
0.80
0.80
0.90
0.80
0.80
0.90
0.90
0.70
0.90
1.10
1.10
1.10
0.75
0.75
0.90
74LS2457A 0.70
74LS2584 0.70
7415259 1.20
7415260 0.75
7415266 0.60
74LS273 1.25
7415279 0.70
7415280 1.90
7415283 0.80
7415290 0.80
741529214.00
74LS293 0.80
74LS295 1.40
74LS297 74.00
7415298 1.00
7415299 2.20
74L5321 3.70
741S3226 3.90
74C SERIES
74C00
74C04 0.50
74C08
74010
74020
74032
74042
74048
74C73
74C74
3.00
3.20
2.00
1.00
740175
740193
740194
740195
74LS395A
1.00
74C221
7415399 1.40
7415445 1.80
7415465 1.20
7415467 1.20
74L5490 1.50
74L5540 1.00
7415541 1.00
7415608 7.00
7415610 25.00
74C244
74C245
74C373
74C374
74C902
0.50
0.50
0.52
0.50
1.00
1.50
1.50
1.00
1.20
1.00
2.00
2.25
74076
74C83
74085
74C86 0.50
74090
1.90
74093
1.50
74C95
1.60
740107 1.00
5.00
0.70
0.70
74C 160
740161
0.75
740162
740163
740173
1.80
1.80
1.80
1.80
1.00
1.50
1.50
1.50
1.50
1.50
1.30
0.95
1.30
4.50
3.25
0.60
3.50
2.25
2.25
1.25
2.00
7415640-1 3.00
7413641 1.50
7413642 2.50
7410642-I 3.00
74L5643 2.50
74LS643-1 3.00
74L5644 3.50
74LS645 2.00
74LS645-1 4.00
74L5668
74L5669
74L5670
7415682
74L5683
7413684
74L5887
7415688
0.70
74C150
740151
740157
74LS612 25.00
7415624
74L5626
7415628
7415629
74L5640
0.70
0.70
74C14 0.50
74LS323
7413324
7415348
74L5352
7415353
7415356
7415363
74LS364
7415365
74L5366
7415367
7415368
74LS373
74LS374
74L5375
74L377
7415378
7415379
74L5381
74L5385
7415390
7415393
1.20
1.20
2.10
1.80
1.80
0.70
0.90
0.90
1.70
2.50
3.00
3.50
3.50
3.50
74C 174
2.00
2.50
2.50
2.00
2.25
2.25
2.25
1.20
740911
74C912
9.00
4.50
74C922 6.00
740923 6.50
740925 6.50
74C926 7.50
74ALS SERIES
7461S00 0.45
7461S02 0.45
7461SO4 0.50
7461S08 0.50
7461510 0.45
746L520 0.45
74ALS32 0.45
74ALS74 0.70
74613138
74613139
74613244
74610245
746L0573
746L5574
74615580
1.50
ISO
4.00
4.75
2.60
4.50
2.60
4000 SERIES
4000
74S SERIES
74511
74S20
74S22
74S30
74532
74537
74538
74540
74S51
74564
74574
74585
74586
745112
745113
74S114
745124
745132
745133
745138
745139
745140
745151
745153
745157
745158
745163
745169
745174
745175
745188
745189
745194
745195
745196
74S200
74S201
0.50
0.50
0.50
0.50
0.50
0.50
0.75
0.50
0.50
0.50
0.60
0.60
0.60
0.50
0.60
0.45
0.70
4001
4002
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
1.00
4022
4023
4024
4025
4026
4027
4028
4029
4030
0.60
4031
1.80
1.80
1.00
1.50
1.50
4032
4033
4034
4035
4036
4037
4038
4040
5.50
1.00
1.50
1.20
1.20
3.00
2.00
2.00
3.00
5.50
3.00
3.20
1.80
1.80
3.00
3.00
3.50
4.50
3.20
745225 5.20
745240 4.00
745241 4.00
745244 4.00
745251 2.50
745257 2.50
745258 2.50
745260 1.00
745261 3.00
745283 2.70
745287 2.25
745288 2.00
745289 2.25
745299 4.50
74S373 4.00
74S374 4.00
745387 2.25
4081
4082
4085
4086
4089
4093
4094
4095
4096
4097
4098
4099
4501
4502
4503
4504
4505
4506
4507
4508
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4060
4063
4066
4067
4068
4069
4070
4071
4072
4073
4075
0.20
0.24
0.25
0.70
0.25
0.60
0,45
0.60
0.24
0.25
0.36
0.60
0.70
0.38
0.55
0.60
0.80
0.80
0.60
0.70
0.30
0.48
0.24
0.90
0.40
0.60
0.75
0.35
1.25
1.00
1.25
2.50
0.70
2.50
LINEAR ICs
0.85
0.25
0.25
0.24
0.25
0.80
0.75
AD7581 12.00
1.20
0.35
0.90
0.95
0.90
2.70
0.75
0.99
0.36
0.55
0.36
0.95
3.60
0.90
0.35
LM723
LM725CN
LM1014
LM1801
1.15
DAC0800 3.00
4522
4526
4527
4528
4529
0.80
0.70
0.80
0.65
DAC:0808 3.00
4532
4534
4536
4538
4539
4541
4543
4553
4555
4556
4557
4560
4566
4568
4569
4572
4583
4584
4585
4724
14411
14412
14416
14419
14490
14495
145000
14599
22100
22101
22102
40014
40085
40097
40098
40100
2.40
DG308 3.00
HA1366 1.90
CL7106 6.75
CL7611 0.95
CL7650 4.00
CL7660 2.50
CL8038 4.00
CM7555 0.90
CM7556 1.40
LC7120 3.00
LC7130 3.00
LC7131
3.50
LC7137 3.50
1.20
LF347
0.60
LF351
0.90
LF353
LF355
0.90
LF356N 1.10
LF357
1.00
4.00
LF398
1.70
LM'OCLH
0.45
0.90
0.48
0.60
LM301A 0.30
LM307
0.45
1.00
0.75
0.65
3.80
2.50
0.75
0.75
0.90
0.70
1.00
2.40
0.36
0.50
.2.40
1.40
1.40
7.50
7.50
3.00
2.60
4.20
4.50
6.50
2.00
3.50
7.00
7.00
0.48
40102
40103
40104
40105
40106
40107
40108
40109
40110
40114
40147
40163
40173
40174
40175
40192
40193
40194
40244
40245
40257
40373
40374
80C95
80097
80098
MC1310P
1413
MC1458
MC1495
MC1496
1.60
LM339
LM348
LM358P
LM377
0.40
0.60
0.50
3.00
LM381N
3.00
NE529
2.20
NE531
1.20
1.90
NE544
NE555
NE556
NE564
NE565
NE566
NE567
NE570
NE571
NE592
NE5532P
NE5533P
NE5534P
NE5534AP
1.50
1.25
1.30
LM186N-1 1.00
2.00
1.20
1.50
0.48
0.55
3.20
0.80
2.25
2.25
2.80
1.00
1.20
1.00
1.00
1.00
1.00
1.00
1.50
1.50
1.80
1.80
1.80
0.75
0.75
0.75
LM384
0.22
0.60
4.00
1.20
1.50
1.25
4.00
3.00
0.90
1.50
1.60
1.20
1.50
OP-07EP 3.50
PLLO2A 5.00
RC4136 0.55
RC4151 2.00
RC4195 1.50
RC4558 0.55
550240 9.00
SAA1900 16.00
SFF96364 8.00
3.25
2.20
01490
3.00
SN76013N
SN76023N
SN76033N
SN76115N
3.00
3.00
3.00
2.15
SN764894.00
SN76495 4.00
SN76660 1.20
SP0256AL2 7.00
LM387 2.70
34391
1.60
LM392N 1.10
LM393 0.85
LM391CH
4.00
LM709
0.35
TBA920
TBA950
TC9109
TCA210
TCA220
TCA270
TCA940
2.00
2.25
5.00
3.50
3.50
3.50
1.75
TD410044 5.00
TDA1010 2.25
TDA1022 4.50
TDA1024 1.10
TDA1170S 3.00
TDA2002 3.25
TDA2003 1.90
TDA2004 2.40
TDA2006 3.20
TDA2020 3.20
TDA2030 2.50
TDA25935.00
TDA2653 7.00
TDA3560 7.50
TDA3810 7.50
TDA7000 3.50
7E61002 7.00
SP8515
TA7120
TA7130
TA7204
TA7205
TA7222
TA7310
7.50
1.20
1.40
1.50
0.90
1.50
1.50
TL062
TL064
lA FIXED
71082
TL083
TL084
TL094
71430C
7905
7906
7908
1.00
0.60
0.60
0.55
0.36
0.35
0.65
0.60
0.60
0.80
0.80
0.85
0.70
0.85
0.40
2.30
0.25
0.24
0.24
0.24
0.24
0.24
0.24
VARIABLE REGULATORS
LM305AH
LM317T
TO -220
1Q3
LM317K
LM337T
10A+VAR
LM350T
10A+VAR
LM396K
LM723N
78HHO5KC
56 5V
78HGKC
5A+VAR
IA+VAR
78GUIC
79HGKC
'IA -VAR
79GUIC
'A -VAR
2.00
4116-20
1.50
1.20
8088
17.50
8741
15.00
8748
12.00
12.00
TMS9960 14.50
2.90
1.90
1.80
1.90
2.75
UPC592H 2.00
UPC1156H 3.00
UPC1185H 5.00
00210
4.00
002206 4.50
X02207 3.75
002211
X02216
5.75
6.75
002240 1.20
ZN404
1.00
ZN414
0.80
ZN419P 1.75
ZN423E 1.30
ZN424E 1.30
ZN425E83.50
ZN426E83.00
ZN427E86.00
ZN428E84.50
2N429E82.25
ZN447E 9.00
7.50
ZN449E 3.00
ZN450E 7.50
3.00
ZN1034E 2.00
ZNA1040 8.60
23.00
ZNA234E9.50
SWITCHING REGULATIONS
ICL7660
G3524
TL494
11497
78540
RC4195
TECHNOMATIC
LTD
MAIL ORDERS TO: 17 BURNLEY ROAD. LONDON NW 10 1ED

SHOPS AT: 17 BURNLEY ROAD. LONDON N W 10
Tel: 01-723 0233 4 lines. Telex: 922800
305 EDGWARE ROAD. LONDON W2
2.50
2.90
5.50
7.50
Z800
Z80H
SUPPORT
DEVICES
12.00
2651
2816-30 20.00
3242
3245
6520
6522
6522A
6532
6551A
8.00
4.50
3.00
3.50
5.50
4.80
6.00
6821
68821
6829
6840
2.50
12.50
3.75
6.00
68840
6850
1.80
68950
6852
6854
68854
6875
2.50
2.50
6.50
8.00
5.00
8154
8155
8156
8.50
3.80
3.80
8205
8212
8216
2.25
2.00
8224
8226
8228
8243
P.O.A
4.25
5.50
2.80
8250
12.00
8255AC-5 3.20
8256
18.00
8257C-5
54.00
8259C-5 4.00
8271
P.O.A
8275
29.00
8279C-5 4.80
8282
4.00
8284
8287
8288D
8755A
4.60
3.80
6.50
16.00
1.80
1.20
1.20
1.20
1.00
OCP71
ORP12
091.60
ORP61
SFH205
TIL32
0.55
TIL78
0.55
TIL31 B
1.20
TIL81
140
TIL100
350
540
640
FND500/TIL730
1.00
FN0507/TIL729
1.00
MAN71/01707
1.00
400
15.00
0 50
5 75
CRT5027 18.00
CRT5037 12.00
CRT6545 9.00
EF9364 8.00
EF9365 25.00
EF9366 25.00
EF9367 36.00
MC6845SP 6.50
4164-15
SFF96364 8.00
TMS9928 10.00
MC6847 6.50
1.50
4164.1511
3.00
4164
2.00
2.00
3.50
2.50
4164-20
4416-15
4532-20
4816AP/3
IC
2.00
4.00
4.00
5101/5501
5514/5114
ADC0808 11.90
AD561 J 20.00
AM25S10 3.50
A0251625213.50
AM25LS25383.50
AM261531 1.20
614261532 1.20
AM7910DC 25.00
DAC80C81-V
26.00
6.00
6.00
5516
5517AP
6116P-3 3.50
6116LP-3
6264-12 12.00
6264P-157.50
6264LP-15
3.40
6.00
DP8304 3.50
DM8131
6514-45 4.00
6810
2.00
DS3691
745189
745289
1.80
2.25
DS8831
93415
6.00
7.50
6.00
93L422
93425
4.00
2.50
2.00
2.00
1.80
2.25
1.80
2.25
745287
745288
74S387
1.50
82523
825123 1.50
825129 1.75
EE PROM
2816-30 15.00
2K+8 30.00
9306 256bi1s
(16816) 4.50
RED T112090.12
GRN TIL2110.18
YEL TIL212 0.20
Rect LEDs
(R/G/Y) 0.30
6.50
7.50
4.00
AY53600 7.50
740922 5.00
740923 6.00
0.90
0.60
0.60
GENERARS
75365
75450
75451
75452
75453
75454
75480
75491
75492
1.50
75107
75108
75109
0.90
0.90
75110
75112
75113
75114
75115
75121
75122
0.90
1.20
1.80
1.20
1.40
1.40
1.40
1.40
1.20
10 LED
2.25
MAN66102.00
NSB58815.70
TIL311
6.50
TIL729
1.00
7117300 1.00
1.50
2.50
9368
9p
18pmn
16p
24p1n
10p
2013.3
1p
22pin
20p
28p n
40pn
RATOTE
COM81168.50
40728
7.50!
UART!
1.50
AY31015P
0.65
0.65
3.00
AV51013P 3.0
COM8017
IM6402
1.20
1.20
1.20
1.20
1.20
8T98
1.20
81L95 1.40
81L596 1.40
81L597 1.40
811_598 1.40
88L5120 4.50
3.00
4.50
MODULATORS
3.75
4.50
6601112
6MHz
SOUND &
VISION
12.00
12MHz
9602
9636A
9637AP
3.00
9638
1.90
ZN447E
9.50
CRYSTALS
1.80
1.60
32.768KHz 1.00
1.6432MHz
2.25
2.00MHz 2.25
2.45760MHz(L)
2.00
2.45760MHz(S(
2.50
DIS
CON ROLLER
ICs
2.5MHz
2.50
1.50
3.276L11-11
765A
10.00
6843
8.00
3.5795MHz 1.00
4.00MHz 1.50
4194MHz 2.00
4.43MHz 1.00
FD1771 20.00
4.9152MHz 2.50
F131791 20.00
5.00MHz 1.50
F01793 20.00
FD1797 22.00
6.00MHz 1.40',
6.144MHz1.40
7.00MHz 1.50
WD 1691 15.00
WD214312.00
WD2793
WD2797
7.16MHz 1.75
8.00MHz 1.50
8.867MHz 1.75
27.00
27.00
10.00MHz
10.50MHz
10.70MHz
CHARACTER
11.00MHz
GENERATORS
12.00MHz
14.00MH2
14.31MHz
14.756MHz
15.00MHz
16.00MHz
17.734MHz
18.00MHz
18.432MHz
19.969MHz
20.000MHz
24.000MHz
48.000MHz
R0325131/C 7.50
R032513LC 7.00
TELETEXT
DECODER
;
SAA5020 8.00
SAA5030 7.00
16.00
SAA5041
1.75
5.068MHz
SAA5050 9.00
116MHz
PX01000
1.75
2.50
1.50
3.00
1.50
1.75
1.60
2.50
2.00
2.00
1.50
1.50
1.50
1.50
1.50
1.75
1.75
2.5
12.60
Please note:
All prices are subject to
change without notice.
Only current prime grade
components stocked.
We also stock a wide
range of: Transistors,
Diodes, Triacs Plastic,
Bridge Rectifiers,
Thyristors and Zenors.
Please phone for details.
OPTO -ELECTRONICS
3.00
3.00
3.00
3.00
1.00
1.00
1.00
2.00
2.00
1.20
5.70
1.20
1.00
1.20
0.90
0.90
1.20
1.20
6.50
BPX25
BPX34
BPW21
COY21
0.15
0.18
0.22
LM3914 3.50
LM3915 3.50
LM3916 3.50
UDN6118 3.20
UDN6184 3.20
ULN2003 0.90
ULN2004 0.90
ULN2068 2.90
ULN2802 1.90
ULN2083 1.60
ULN2804 1.90
75491
0.70
75492
0.70
DISPLAY
DRIVERS
1150
MC14411 7.50
I
8728
8795
8796
8797
FN0357
MAN74/DL704
MAN71/DL707
MAN4640
MAN6610
74C925 6.50
74C926 6.50
6.50
74928
7216B 22.00
ZN1040 6.70
1.00
MAN8910
MAN8940
0.80
0.50
0.50
0.70
0.70
BAUD
8T26
COUNTERS
CXO (8i colour
LOW PROFILE SOCKETS BY TI
lip
8.50
2.25
2.25
5.50
5.50
TIL220
TIL222
TIL226
675
250
14pin
16pin
4.75
MC3480
MC3486
MC3487
MC4024
MC4044
LEDs
3.50
8pin
Y52376
0.125"
4.50
4.50
2 50
3 00
MCS3170
MC6883 16.00
MC14411 7.50
MC14412 7.50
9374
1.75
2.00
1.50
DS8832 1.50
058833 2.25
DS8836 1.50
DS8838 2.25
D7002 8.00
MC1488 0.60
MC1489 0.60
MC3446 2.50
MC3459 4.50
9370
MAN3640
MAN4640
1.20
2 20
5.00
3.50
DS8830 1.40
PROM.
28L22
24S10
185030
18SA030
745188
KEYBOARD
E NCODE Rs
75154
75159
75160
75161
75162
75172
75182
75188
75189
INTERFACE
AD7581 15.00
225
650
12.00
MC6845 8.50
0.75
FND357 1.00
40
25
CONTROLLER
3.00
Bar Graph:
Red
2.25
1.20
12.06
27512 P.O.A
27512-2514.00
TMS2718 5.00
41256-207 0.50
41256-157 0.50
Green
250
2
41256.15
1.20
9 00
27256-25 4.00
27256-30 26.09
EF9369
OTHERS
2N5777 0.50
BPX25 1.80
BPW2I 2.80
27126-25)2.50
216-150
1.60
8251A
3.25
8253C-5 3.50
6.00
27C64-25
17258
4116
8087
5.50
2764-25 2100
MEMORIES
Z80
Z80
ULN2068
ULN2802
ULN2803
ULN2804
UPC575
280ADMA 7.50
8035
80C35
8039
OTHER REGULATORS
FIXED REGULATORS
IA 5V
LM309K
LM323K
3A 5V
78H05KC
5A 5V
78H12
5A 12V
78P05
10A 5V
Z800MA 7.00
7.00
Z808P10
5.00
2808CTC 5.00
Z808DART 9.00
1.10
1.00
0.60
0.55
0.50
0.60
0.80
6.00
8.50
28060501 7.00
1.10
0.75
0.75
0.50
0.50
7912
0.45
0.50
7915
0.15
7918
0.50
0.50
0.50
7924
0.50
to FIXED VOLTAGE PLASTIC 1092
5V 79L05 0.45
51/ 78105 0.30
12V 79L12 0.50
6V 78106 0.30
15V 79L15 0.50
8V 781.08 0.30
12V 78L12 0.30
15V 78115 0.30
27326-30
27326.35
1.50
2532-30 5.50
2.75
4.00
ULN2003A
ULN2004A
0.50
0.50
0.50
0.50
4.50
3.50
5.50
4.50
9.50
Z80ACTC
Z80DART
2147
1.20
UCN5801A 6.00
ULN2001A 0.75
ULN2002A 0.75
-VE
0.45
8.00
2708
2716+5V
2716-35
2732
2732A-2
2532
2.50
TMS9995 18.00
3.20
ZNAI34H
2564
Z80APIO 2.75
ZBOCTC 2.50
TM51601
UA759
UA2240
ZN459CP
Z8OPIO
0.60
0.90
0.40
0.70
UAA1003-3 9.35
ZN448
2516+5V 3.50
2516-35 5.50
Z80AS10/0/2/9
3.50
6.00
4.20
80039
7.00
80806
4.20
8085A
3.00
80085A 7.50
8086
22.00
PROM,
11454500 14.00
TM59901
5.00
TMS9902 5.00
TMS9911 18.00
TMS9914 14.00
68000 -LB 36.00
1.20
VOLTAGE PLASTIC 70220
+VE
1802CE 6.50
26504 10.50
6502
4.50
65CO2-2MHz
12.00
6502A
6.50
6502B
8.00
6800
2.50
6802
3.00
6803-2 12.00
6809
6.50
6809E 10.00
68809 10.00
68809E 12.00
4.00
2101
4.00
2102
2.50
2107B
5.00
21116-35 4.00
2114
2.50
2114-2
3.50
0.35
0.55
0.75
1.00
2.00
TL081
VOLTAGE REGULATORS
5V 7805
6V 7806
6V 7808
12V 7812
15V 7815
18V 7818
24V 7824
CPU/
TL061 CP 0.40
TL072
TL074
3.00
L5/1383
0.80
0.90
0.90
0.75
TL071
LM380N 1.50
150381 AN1.70
0.36
0.40
T84800
T8A810
T8420
TBA820M
2.00
MM6221A
4.00
1.20
0.70
LM380N-8 1.50
1.20
MC3401
LM324 0.45
LM334Z 1.15
LM335Z 1.30
LA/1336
0.75
0.45
3.00
0.70
COMPUTER COMPONENTS
:
186231
MC3340P
1.50
1.80
LM319
1.50
MC3403 0.65
MF10CN 4.10
MK502409.00
ML902 5.00
4.00
ML922
4.50
LM318
1.80
3.50
LM3915 3.40
LM3916 3.40
LM13600 1.50
M51513L 2.30
M51516L 4.50
M83712 2.00
LM308CN 0.75
2.25
L A/1310
LM311
0.60
1.50
40101
LM3911
LM3914
CA3280G 3.00
D7002
6.00
0601408-8 3.00
4521
4531
3.00
2.50
3.00
LM1872 3.00
LM1886 6.00
LM1889 4.50
LM2917 3.00
LM3302 0.90
LM3900 0.80
LM3909 1.00
LM7871
CA3130E 0.90
CA3130T 1.30
CA3140E 0.45
CA3140T 1.00
CA3146 2.25
CA3160E 1.50
CA3161 E 2.00
CA3162E 6.00
CA3189E 2.70
CA3240E 1.50
0.55
2.20
0.48
0.32
0.60
1.50
LM1830
CA3890A0 3.75
0.55
0.55
0.55
3.00
0.65
0.22
LM7747 0.70
LM748 0.30
LM1011 4.80
LM741
CA3020 3.50
CA3028A 1.10
063046 0.70
CA3059 3.25
CA3060 3.50
CA3080E 0.70
CA3385 1.50
CA3086 0.80
CA3089E 2.50
1.20
0.48
1.00
0.60
LM733
CA3D19A 1.00
1.10
1.10
4520
136710
LM711
ADC0808 11.90
AM75105C 25.00
2.00
691113
AN -1-5050 1.00
AY-3-1350 3.50
AY-3-8910 4.90
AV -3-8912 5.00
1.50
4551
7410783 16.00
74S00
74502
74504
74505
74S08
74510
4076
4077
4078
MAN89100.8"
NSB5881
ORP12
SFH305
TIL31A
T1L32
TIL78
TIL81
TIL100
TIL311
OPTO-ISOLATORS
IL074
MCT26
MCS2400
MOC3020
1.30
11074
2.20
0.70
0.70
0.70
0.70
3.60
1.75
TIL111
711112
1.00
1.90
7I1113
TIL116
6N137
6N139
150
WIRE WRAP SOCKETS BY TI
24p
26p
30p
8pl3
14pin
16p1n
25p
35p
40p
/8pin
SOp
2opin
80p
85p
225.13
24pin 70p
28pIn 809
40pin 100p
300
2.25
2 50
1 50
TURNED PIN
LOW PROFILE SKIS.
8pin
14p1n
25p
30p
16pin
113pm
35p
40p
20p1n
24pm
45p
55p
28pin
40pin
65p
90p
PLEASE ADD 50p p&p & 15% VAT

(Export: so VAT. p&p at Cost)
Orders from Government Depts. & Colleges etc. welcome.
Detailed Price List on request.

Stock items are normally by return of post.
Minimum 'I elephune Order 5
91
RALFE
ELECTRONICS
TEL: 01-723 8753
CHAPEL STREET, LONDON.
TEST EQUIPMENT
BRUEL & KJOER 2409 voltmeters
60
PHILIPS PM6307 wow & flutter meter
325
STC attenuators DC -1 MHz 0-100db
25
ROHDE & SCHWARZ SWOB polyscop 400MHz
150
ROHDE & SCHWARZ USVH selective uV-meter
100
HUGHES spot welding supplies 100W/sec
125
NM52A
interference
receiver
STODDART
GHz
350
EDDYSTONE EC958 communications receiver
650
SYSTRON-DONNER frequency counter 6050
50MHz
95
SYSTRON-DONNER frequency counter 6051
200MHz
195
RADIOMETER FRA3 Audio wave analyser
250
AIRMEC 10KV ionisation tester
85
BOONTON 77B capacitance bridge
150
125
SIERRA power meter 1-50W 144-470MHz
KORTING 82512 colour pattern gen
125
345
CITRONIC 900W audio power amp 1/2 -price
BRYANS X -Y -T Plotter type 22020
175
FARNELL pulse generator system
75
BPL Component comparator
150
VALVE TESTER made for US Navy type TV10DU
* * STEPPER
MOTORS *
Brand new stock of 'ASTROSYN' Type

20PM-A055 stepper motors, 28V DC, 24
steps per rev. 15 oz-in torque rrr 100PPS.
Body length 21 ", diameter 2", shaft 1/4" diam
x 4,/4" spirally threaded. Weight 16oz. Price
each
11.50
(p&p
50p).
Connections
supplied. INC VAT.
PHILIPS CONTROLS CORP. 14V 48 Step per
Rev 4 -phase 2.75" diameter. 5 each + VAT
'OSCILLOSCOPES'
inc. vat.
350
3490A digital multi-meter
650
8733A pin modulators
851B/8551B spectrum analyser 1K5
250
4204 audio oscillator
1K5
8552A I.F. unit
202H AM/FM sig. gen
8701A/2A/3A link analyser
8557A/182T Spectrum analyser
8007B Pulse generator
8555 spectrum analyser unit
8556 spectrum analyser und
1K5
150
350
4,500
....400
2,750
1,750
CONSTANT VOLTAGE
TRANSFORMERS
35
ZENITH 240V Output 240W
65
ZENITH 240V Output 500W
CLAUDE-LYONS 220V 550W sine125
wave, new
ESCAP DC MOTORS
SERVOMEX servo-controlled 3KW

SERVOMEX servo-controlled 5KW
5.25
CLAUDE-LYONS
type, new
(E -equip tested 8 guaranteed
350
225
HP SPECTRUM ANALYSER
400
350MHz
350
250
Hewlett Packard model 182T fitted with type 8557A

350MHz spectrum analyser plug-in. 4,500.
MARCONI TEST EQUIPMENT
HP SPECTRUM ANALYSER
110MHz
Li. t.ti
Hewlen-Packard spectrum
analyser
system comprising 8553L 0-110MHz RF
unit. 8552A I.F. unit installed in a type
1406 main frame. Excellent condition.
2,950
with manuals. One off only
+ VAT
HEWLETTPACKARD
EQUIPMENT
8553LR.F. unit 110MHz
Swiss -made precson 6V DC motors with 70m reduction gearboxes, giving final drive speed of 16RPM (e
6V. Diameter 212cros x 4cms long. PRICE INC. VAT
X400
r -
p&p 50p
CARRIAGE
IONIZATION type smoke detectors ZITON' model

type Z310 -1M. Brand new units supplied complete
with mounting plates. Similar to RS type 300-473.
List price 32 each. OUR PRICE 7.50 (p&p 50p)
TEKTRONIX 7A18 Y.Amp

TEKTRONIX 442 35MHz
TELEQUIPMENT D63 3 -trace 15MHz
TELEQUIPMENT 085 50MHz
TELEQUIPMENT D75 50MHz
TELEQUIPMENT 067A 25MHz
200
TELEQUIPMENT D66A 15MHz
TEKTRONIX
100MHz
storage
7613
2,500
main-frame
395
HITACHI V422 40MHz
350
TEKTRONIX 5103 main frames
Also scopes by Trio, Hameg, Hitachi etc.
please
changing,
Stock
continually
phone.
1125
2K5
Invitation to tender for your surplus to requirement

electronic test equipment, computer gear etc. Please
send list or phone our buyer.
SMOKE DETECTORS
TEKTRONIX 7L5 spectrum analyser P.I. 5MHz
WANTED
NW1
10
125
t75
220V 6KW servo
250
WE HAVE IN STOCK A WIDE RANGE OF POWER SUPPLY

UNITS, AVO MULTI -METERS. INSULATION TESTERS.
COMPUTER PERIPHERAL EQUIPMENT ETC. ETC. WE
WOULD BE PLEASED TO RECEIVE YOUR ENQUIRY
REGARDING ANYTHING ELECTRICAL OR ELECTRONIC.
TF2300 modulation meter

400
TF144H 72MHz signal generator
75
TF868 univeral bridge
65
TF2301 modulation meter
150
TF1066B sig. gen AM/FM to 470MHz
350
TF99513/5 sig. gen. AM/FM to 220MHz
300
TF995A/5 sig. gen. AM/FM 1.5-220MHz
200
TF2604 electronic multi -meter
145
TF893A audio power meter
75
TF2330 audio wave analyser
250
TF2002 signal gen. to 72MHz
400
TF791 D deviation meter
100
TF2606 differential DC voltmeter
125
TF1152A RF power meter 50 ohm 25W
65
TF2612 anenuator
100
TF2430 80MHz frequency counter 125
TF2700 universal bridge
250
2540 Communications receiver _. 2,500
DRE 4000A DRIVES

Data Recording Equipment Model 4000A5 + 5MB
Top -loading disc drives in stock. Brand new
including full technical manual. Few remaining
250 each + VAT.
SPECTRUM ANALYSER
HEWLET PACKARD spectrum
analyser 0.01-350MHz plug-in
unit type 8557A fitted in type
1827 main-frame. Immaculate
condition, very little used.
4,500 + VAT.
With manuals
PLEASE NOTE: All our equipment is sold in

excellent condition, fully functional and
guaranteed for 90-days. Mail orders welcomed, please telephone for carriage quote on
any equipment. ALL PRICES ARE PLUS VAT
PLEASE.

5A
Jk
PyP
Q.
Pp00 o 3
AFFORDABLE ENGINEERING SOFTWARE
P0
f1
EXTENSION
't -WAYSOCKET
vt`1
fjjll WITH LEAD & 13A PLUG
4
ELECTRICAL
13A PLUG 46P
2 -WAY ADAPTOR 90P
13A SWITCHED DOUBLE SOCKET3.45

TRANSISTORS
28p
30p
AC127
'C128
AL 176
30p
Ar,88
280
42p
52p
lOp
lOp
lOp
lOp
A0161
AD162
BC107
BC108
BC109
BC182
BC183L
BC212
lop
lOp
C-MOS
4000
19p
4001
4011
24p
23p
35p
54p
4013
4017
I.C.S
45p
LM324N
LM380-8
LM380-14
LM1458N
LM3900N
NE555
74LS
00
02
04
20
32
38
f1.15
f1.80
98p
85p
25p
24p
24p
24p
24p
24p
24p
44p
48p
60p
44p
75
90
132
138
12V RECHARGEABLE UNIT

AN ENCAPSULATED PACK OF 10
SIZE NI -CAD
BATTERIES IN
A BLACK
PLASTIC
CASE, COMPLETE
WITH INLET &
OUTLET SOCKET
(XLR TYPE) AND FUSE HOLDER. THIS UNIT
WHEN CHARGED GIVES 12 VOLTS OUTPUT.
ALTERNATIVELY, THE UNIT CAN BE CUT
OPEN AND THE CELLS REMOVED TO BE
USED AS NORMAL D CELLS, IN TORCHES, TOYS ETC.
SIZE APPROX: 245 x 75 x 75mm
PRICE f5.99+ 1.85p&p + 15%VAT.
CANON PLUG TO FIT ABOVE UNIT1.50ea.
NI -CAD BATTERY CHARGER
THIS BATTERY CHARGER IS SUITABLE

FOR AM, M, C, D & PP3 TYPE NI -CAD
CHARGING AND CAN COPE WITH UP TO 4
OF EACH AAA, AA, C&D PLUS 1 x PP3
AT ANY ONETIME.
+
3.35
5.75
4.75
7.95
15.25
19.70
PORTABLE GAS SOLDERING IRON
13.90
SPARE TIPS 4.50 EACH
SIZES 2.4, 3.2 AND 4.8mm
MARCO TRADING
DEPT. EWW 11 THE MALTINGS,
HIGH STREET, WEM,

SHROPSHIRE SY4 5EN
TEL: (0939) 32763 TELEX 35565
15% VAT
NORMALLY 5.17
RECHARGEABLE BATTERIES NI -CADS)

A RANGE OF NICKEL CADMIUM BATTERIES
WHICH WILL REPLACE DRY BATTERIES.
CAN 8E QUICKLY AND EASILY RECHARGED
USING THE ABOVE NI -CAD CHARGER.
AA
95p each
10+ 85p each
C
f2.14 each
10+ f1.98 each
D
f2.30 each
10+ 2.10 each
PP3 - 3.75 each
10+ 3.65 each
24
HOUR
ANSAPHONE
SERVICE.
B. T.

92
Signal/System Analysis
Active Filter Design Analysis
Static Thermal Analysis
Matrix Manipulation
Scientific Graph Printing
PC/XT High Res. Graphics
Proof Reader and Style Analyzer
Just 70 each plus VAT and 2.00 p&p
SPP
ACTFIL
STAP
MATRIX MAGIC
PLOTPRO
PCPLOT2
RIGHTWRITER
ALL the above Programs are for PC/MSDOS, SOME are also
available for CP/M-80; please enquire.
ALSO AVAILABLE
LOW COST R.F. design Software STAR 1.0
utilizes S parameters to analyze and optimize Amplifiers,

Filters, Oscillators, Matching Networks etc. (Available for
PC/MSDOS only).
An unbeatable buy at just 100 + VAT and 2.00 p&p.
QUADRANT COMMUNICATIONS LIMITED
APPROVED
MASTER SOCKET 2/4A

SECONDARY SOCKET 2/6A
4 -WAY LINE PLUG 4310
LINE JACK CORD WITH PLUG
AC Circuit Analysis
DC Circuit Analysis
AND MICRO
Analyses and designs Micro Strip Circuits, Lowpass, Highpass,
Bandpass Filters, Impedance Transformers, Coupled Strips etc
Contains Fringing Corrections for accurate "real world" results
the first time.
200 + VAT and p&p.
Runs under MSDOS.
4.50
RESISTOR KITS
1/4W 5 EACH VALUE 305)
1/4W 10 EACH VALUE (710)
1/2W 5 EACH VALUE 365)
1/2W 10 EACH VALUE (730)
1W
5 EACH VALUE (365)
2W
5 EACH VALUE (365)
Root Locus
LOCIPRO
ACNAP
DCNAP

b`
j."dhQ`
OoJQ `rTy
co
2.85
1 95
30p
WICKHAM HOUSE, 10 CLEVELAND WAY, LONDON El 4TR

Telephone: 01-790 2424 Telex: 24224 (Ref W6111)
1.25
CIRCLE
10 FOR
FURTHER DETAILS
17630
Charge -coupled device

technology
Extensive development of a charge -coupled
pick-up device has led to a high performance
camera that should be ideal for electronic news
gathering
KATSUMI SHINODAAND E. TAMURA
The last two or three years has seen
application of charge -coupled devices

in consumer products in quantities
exceeding a million per year. Sony's c.c.d.
chip production now exceeds 100,000 per
month. The benefits of use of such massive
production enables excellent yields of quality c.c.d. chips for professional use.
The most suitable and effective ways in
which c.c.ds can be used are those in which
the advantages of not only small size, low
power consumption but also high sensitivity, low lag, reduced sticking are most
important. The most obvious broadcast application is for e.n.g. particularly for lightweight combined camera and v.t.r. in which
mobility and handling ability can be dramatically improved.
The currently available c.c.d. still has
some practical limitations however compared with conventional tubes, and special
care is needed in the camera design to
compensate for these drawbacks and at the
same time make good us of the c.c.d's
beneficial characteristics.
Four -phase
Vs9
clock pulses
a4
a3
a2
V -registers
OFD
DESIGN GOALS
Compact, lightweight, low power consumption without any sacrifice of reliability
and robustness.
High picture quality. The c.c.d. chips
used are of the best that can currently be
made but the number of pixels in the horizontal direction and the dark current are
limitations in comparison with tubes. Various strategies can be applied to realize
comparable picture quality.
Ergonomic design. Much experience
has now been obtained from previous tube
modules including user advice and opinion.
This enables the camera to be a wellbalanced rigid mechanical design.
The main chip characteristics are shown

1 and the physical structure in Fig.
1. The parameters are typical values, there
being some spread in practice. However, a
large production quality enables selection of
chips specifically for high quality broadcast
applications. The three main criteria are
freedom from blemishes, low dark current,
and high saturation capability.
in Table
Three devices are used and several

methods are available to implement an
imaging system. After careful consideration
the conventional beam -splitting prism was
Output
H-register
Fig.1. This c.c.d. imager comprises m.o.s. photosensors arranged as rows of 500
elements and columns of 582 elements. In the inter -line transfer technique both
photosensor and vertical shift register are "interlined" on the same chip in about half the
size of the frame transfer type chips.
used on which the three chips are attached.

Thus RGB signals are available in line with
tube practice.
Furthermore, as shown in Fig.2, the
fixing of the G and the R,B devices are
horizontally displaced by half a pixel pitch
from the nominal position. Each device has
510 elements in the horizontal direction and
spatial offset allows a higher luminance
resolution to be obtained than normally
expected from this number, at the same time
maintaining satisfactory chrominance resolution.
Other advantages are:
- High efficiency in the input light handling

enabling good sensitivity to be achieved.
- Colour rendering can be controlled by the
prism block design and existing know-how
SG, SR, SB are

aliasing components
of G, R, B
ccd-1
Base hand
(G)
ccd-1
(G)
`2,
APLik
\
FREOUENCY
ccd-1
(G)
Fs1P
SR.SB
Fig.2. To increase horizontal resolution a

spatial offset technique is used that shifts
pitch by half an element. Resolution of 550
tv lines is achieved.
93
o\
1st cycle
I
u_
II
Vertical (blue)
0 05
25'
-T
2nd cycle
..-- 3rd cycle
11
-----Horizontal(red)
0.00
1.3
0 10
- - - Horizontal
I
----Vertical
i
<?)2525
--2.
25
-005
blue)
(red)
__._
`
_ 1/
Table
25
-20
Numbers indicate temperature in deg.
-010
Charge -coupled chip paran-
Item
Spec. (typical)
Image format
Sensitivity, 1000/lux'
2/3in
160mV
530mV
Saturation
Dark signait
Dark Shadingt
Smear
Gamma
14mV
3mV
0.01%
1
Not visible
Lag
cc
1.
II
3200K with infra -red filter
t at 55C
Fig.3. Errors in registration between the three primary devices are reduced by bonding
them to three faces of a prism block. The dominant influence on registration, the G -R
component, is very low at the unnoticeable level of 0.02%. Diagram shows consistency
over three temperature cycles.
TABLE 2. Tentative specification
Pick-up device
Picture element
Three-chip2/3in c.c.d
510(h) x 492(v) (NTSC),
500(h) x 582(v) (PAL)
2000in F5.6 (NTSC). F5.0 (PAL)

Sensitivity
Minimum illumination 15lux (NTSC) (+18dB)
20Iux (PAL)
Signal-to-noise ratio
58dB (NTSC), 55dB (PAL)
Horizontal resolution 550 tv lines
Registration error
0.05% (all zones)
Filter
Clear, 5600 K+1/4ND, 5600K,
5600K+1/16ND
Power consumption
10.5W
Gain up
0/9/18dB or 0/9/24dB
Operating temperature -20 to +45C
Weight
3.2kg (without lens)
three -tube camera normally has a signal handling

capability of 400%, the c.c.d. camera has a dynamic range of up to 600% by virtue of the
automatic knee control scheme shown. Non -additive mixer detects only the highest level
from R,G,B, inputs.
Fig.4. Whereas a conventional
from conventional tube practice effectively

applied.
- Errors due to the optical system can be
easily compensated and the necessary total
characteristics more easily obtained.
It is often assumed that the use of c.c.ds
implies that registration is free from the
need for adjustment. But the use of multiple
chips has its own requirement for accurate
initial registration. Additionally, highly

stable mechanical positions must be maintained for all three chips, in particular the
half pixel offset must be permanently established.
These considerations led to a design in
which the chips are bonded directly to the
faces of the prism block using a specially
made mechanical locating device. With this
method excellent stability can be maintained
for variations in temperature and humidity
and also against mechanical shock.
Fig. 3 shows some typical data in which
the registration drift is plotted against
ambient temperature. The dominant influence on registration, the G -R component, is
very low, being an unnoticeable level of
0.02%.
Sensitivity, s/n ratio and dynamic range
are closely related to each other; with the
94
c.c.d. chip selection process the final parameters are as shown in Table 2.
Sensitivity is about half a stop better than
conventional 17mm (2/3in) plumbicon tube.
Signal-to-noise ratio. A correlated double sampling method suppressed the noise

generated at the output stage. A newly
designed heat dissipation and cooling system limits the temperature rise so reducing
the increase in dark current noise which
occurs with a rise in temperature. Finally,
optimization of RGB spectral characteristics
gives an overall benefit in the signal-to-noise
ratio.
Dynamic range. A conventional three -tube
camera normally has a signal handling
capability of up to about 400%. The c.c.d.
camera, on the other hand, has a dynamic
range of about 600% because of an automatic knee control circuit in the video processing amplifier as shown in Fig.4.
The major parameters given in Table 2 are
for both PAL and NTSC models. The PAL
version is slightly less sensitive because the
effective sensor area is made narrower by the
increased number of pixels in the vertical
direction.
There are still several drawbacks which
must be improved for the future high quality

broadcast colour camera, particulary in respect of number of pixels in the horizontal
direction, dark current, spectral response
and the smear characteristics.
The methods presently used for measuring tube cameras may be inappropriate for
the c.c.d. camera. For example, the measured maximum resolution is below the
value obtained for a tube camera, but the
subjective sharpness is higher, particularly
for the PAL version.
We expect development to continue toward producing higher quality c.c.d. chips
for broadcast use. In the meantime, both
tube and c.c.d. cameras have their individual
uses, the first for high quality studio use, the
last for e.n.g.
Further reading
High resolution c.c.d. image sensors with reduced smear by S. Ochi et al. IEEE Trans Electron Devices, vol.ED-32, no. 8, Aug 1985 pp.
1451-1456.
Katsumi Shinoda is deputy general manager

in product management at Sony Broadcast
Ltd. Previously he was general manager
(broadcast) at Hitachi Denshi GmbH, and
before that, senior technical general manager at ABC-TV, Osaka. Mr Shinoda graduated
from Hiroshima University in 1954.
E. Tamura is manager of Sony Corporation's c.c.d. camera division. He joined as tv
camera designer from Shiba Electric Co in
1972, where he went after graduating from
Gonma Technical College.
BBC Datacast -the
transmission system
A similar process to that used in the teletext system is used
to transmit data-lines which are independent of the

normal teletext system.
J. P. CHAMBERS, M.A., C.Eng., M.I.E.E
hen the specification of the British

teletext systems was written, over
ten years ago, the prime purpose
was to carry pages of text in a fixed format
suitable for display on a domestic television
receiver. This was to be done efficiently,
reliably, ruggedly and at low cost; an objective generally reckoned to have been
achieved. There are now over ten million
receivers world-wide equipped for this
system.
Data is carried on otherwise unused lines
in the television field -blanking interval. Its
service started with two lines per field used
for teletext, but now six or seven are in use.
The specification allows for up to 16 lines per
field to be used, but there are practical
limitations caused by the need for compatibility with existing receivers: the use of lines
too early in the field interval can cause the
data to be displayed on screen during the
vertical flyback period on some receivers,
and using later lines can cause a flared image
at the top of the picture. This problem varies
between countries and some already use
more lines for teletext.
Teletext was designed for receivers capable of storing only one page. It is necessary
to repeat all pages frequently to allow users
freely to choose and acquire pages. So a
resource capable of sending 40 000 pages per
hour is currently used to send perhaps 300
different pages at any one time. Now that
mass semiconductor storage is so cheap it is
possible to think of data bases being updated
by teletext, only new material being sent
with occasional complete replenishments.
Even a small portion of the total capacity
allocated to such a function could provide
very many valuable new data services.
During 1985 the BBC was approached by
several organizations interested in the possibility of using teletext data lines for carrying
data for commercial purposes.
Anticipation of Datacast. When the teletext
specification was written in 1976, 75% of the
address codes at the start of the data lines
were allocated, but the other 25% were
reserved for future use by requiring that the
decoders initially produced should ignore
them.
First hamming -coded byte
_
2
o
o
-1-.-----.......
617
These codes define

the boundaries between
pages of a magazine
These codes relate

to the currently transmitted page of a magazine
i.a
-0
6
7
.- N
N
E 8
G
o
C
N
o a
o U
V1
.O
r-
1
coa
o a o
EZEZEZEZ
a1
cc
co
CCCC
--
-t
G
o
VI
.O
N
c"--
CN
a
a
Er ZEE
al
a1
a a o
E E E
co
Rl
a1
t.
Only codes above this line

were allocated in 1976
`94
D
E
III---""IIIII---
Television service
data line code
These codes
Four codes used
for dota broadcasting
Fig.1. Allocation of the 256 codes available within the
These codes relate to

magazines but not to
particular pages within
a
magazine
relate to
independent data -lines
first two Hamming -coded bytes
of a teletext data line.
This is the only safe way to allow for

exuansion; new data services using different
clock rates, modulation systems or framing
codes would always be liable to interfere with
one another, particularly if decoders are not
designed with knowledge of all the possible
systems. Such problems may remain dormant for many years and then suddenly
appear when particular combinations of data
begin to be used. The only safe way to allow a
teletext-like system, with an audience of
millions, to develop safely is by reserving
codes in the data channel and using them to
introduce new services. Ideally these in turn
still preserve the potential for further developments.
A transmission system, based on the use of
data -lines which were independent of the
normal teletext service, was defined and
experimental broadcasts began on September 10th, 1985. The BBC Datacast service
was announced on October 3rd, 1985 and
the first equipment built specifically to

originate these signals was installed at BBC
Television Centre on March 10th, 1986.
INDEPENDENT DATA-LINES
Each data -line in the teletext format starts
with a clock run-in sequence (cR1) and
framing code (Fc). The next two eight -bit
bytes, known as the magazine and row
address group (MRac), are Hamming-coded
and each carries four message bits. In the
page -organized teletext application, these
eight message bits are interpreted as a
three -bit magazine number (in the range
1-8) and a five -bit row address (in the range
0-31).
The 1976 specification requires that data lines with row addresses in the range 24-31
be ignored. Subsequently it was decided that
row addresses 24 and 25 represent an exten-
95
sion to the page, intended to be stored with

the page and included in its cyclic redundancy check. Row addresses 26,27 and 28 are
used, possibily more than once in each page,
to carry additional information to over -write
characters or to provide special display attributes.
All of these row addresses are still associated only with the current page of their
particular magazine. Row address 0 (the
page header) is used to define the boundaries
between successive pages of a magazine.
The data -lines of different magazines can
be mixed in any way in the transmission
sequence, as the decoder should see each
magazine as a separate data channel. This
independence is only broken by the use of
the serial magazine transmission mode
which allows all incoming page headers,
regardless of magazine, to be presented as
they arrive and so puts an obligation on the
broadcaster to maintain a meaningful sequence when all the page headers are taken
together.
Row address 29 is reserved for applications where information relating to an entire
magazine is being sent. Only row addresses
30 and 31 remain for applications unrelated
to the page and magazine structure of
teletext. Taken together with their eight
`magazine numbers' these provide 16 MRAG
combinations which can serve as the addresses of 16 independent data channels. These
can be used in any way at any time regardless
of the content of the teletext service without
interfering with the normal operation of a
conventional teletext decoder operating
according to the specification.
One of these addresses is used for the
television service data-line3 and four others
are currently being used with BBC Datacast
transmissions, although other formats of
signal can also be used here without interfering with Datacast.
It is possible to depict the above allocation
of magazine numbers and row addresses on a
diagram with eight columns and 32 rows.
Unfortunately this leads to confusion when
it is pointed out, for example, that magazine
8, row 30 does not belong to any magazine
and neither is it row 30 of any page! An
alternative diagram is given in Fig. 1, where
the 256 possible MRAcs are presented in terms
of the contents of their first and second byte.
It will be seen that the 16 combinations
corresponding to the independent data -lines
are selected by the first byte, the second byte
having the fixed message bits 1111. So a test
of the second MRAm byte is sufficient to
separate all the independent data -lines from
those relating to a normal teletext service.
DATACAST PACKET STRUCTURE
The self-contained nature of the Datacast
data -line within the teletext multiplex

makes it appropriate to refer to it as a
Datacast packet.
The Datacast packet format is organized
in eight -bit bytes as shown in Fig. 2, which
emphasizes how certain information in the
early part of the packet influences the interpretation of the later part. Moreover, each
packet stands alone and it can be interpreted
96
User data bytes
Data chonnel
group
CI
FT AL
RI
dummy
byte
DL
shortened
packet
CRC3
CRI
FC
1111
Address
These three
components
are fixed
Fig.2. Structure of a
Datacast packet
16 -stage
stages
stages
Exclusive -or"
(
module -
Input
shift register
gate
adder
Fig.3. Generation and checking of cyclic
without reference to others. Both these

points, which are not generally true of
page -organized teletext, simplify both the
generation and the reception of Datacast
services in applications where several

teletext -based services are multiplexed
together onto a single video signal. It will be
seen that the overheads have largely been
arranged so that they are only incurred when
they serve a function.
The function of the bytes of a Datacast
packet are now considered in sequence.
Data channel group. The first byte of the
of a Datacast packet identifies four
possibilities. These can be used to distinguish between Datacast services arising at
independent sources, such as regional contributions. This makes it possible for the
same addresses to be used by more than one
source without contention, there is no need
for overall control of address allocation.
The data channel group is analogous to
the magazine number of conventional teletext; the same page numbers can be used in
different magazines and they can be originated independently before combining onto a
single video signal. Similarly, the data channel group number is a component of the
complete information necessary uniquely to
specify a Datacast service.
The second MRAc byte of a Datacast packet
carries the Hamming -coded message bits
1111, indicating an independent data-line.
MRAc
Format type byte (FT). This Hammingcoded byte controls the interpretation of
later bytes of the packet. The four message
bits, in transmission order, are:
-0 if Datacast format applies,

-1 if the byte is used later,
-1 if the ci byte is used later,
-1 if the DL byte is used later.
RI
If the first of these bits is set to 1 then the

meaning of the other three is not defined,
neither is the meaning of any subsequent
data in that data -line. This allows new
formats for use with independent data-lines
to be defined without requiring the use of
other data channel groups.
stages
-"
p-
stages
Feedback switch -Logic `0'
Ou
put
redundancy check
Packet address length (AL). The first three
message bits of this Hamming -coded byte
indicate how many immediately following
bytes are Hamming-coded and allocated to
the packet address. The minimum is none,
the maximum is six, giving a 24 -bit address.
The 111 state is reserved to extend the
address capacity in a way not yet defined.
The last message bit is set to 0 when the
access to, decoding and interpretation of this
particular Datacast service is to be protected
from interference by any other teletextbased services. This facility is provided in
anticipation of some proposed uses where
teletext and Datacast services may be used to
control access to other services, including
the option of turning off the decoders.
Packet address bytes. Up to six Hammingcoded address bytes, as signalled by the AL
byte, follow the AL byte. The least significant
bytes are sent first. The least significant bits
within each byte are sent first.
Packet repeat indicator byte (RI). The RI byte

is only present if signalled by the FT byte.
Only then can the packet be repeated unchanged, noting that the RI byte itself does
change.
The first four bits are set to 0 when a new
packet is sent and this number is incremented modulo -16 on subsequent repeats of the identical packet. The next three
bits are not yet defined. The last bit is set to 0
to indicate that no further repeats of that
packet should be expected, but setting to 1
does not necessarily indicate that there will
be a further repeat. This last bit is intended
to assist certain decoder strategies.
Packet continuity indicator byte (CI). The CI
byte is only present if signalled by the PT byte.
It is an eight-bit number incremented
modulo-256 with each new packet of the
same data channel group, address length
and address bytes. It does not change during
repeated transmission of the same packet.
If a ci byte is not signalled, the eight -bit
continuity indicator number is used to modify the CRC byte, so there is always a continuity indicator of one type or the other.
Teletext 8
'Telesoftwar
Teletext
subtitles
Network video
Dstributicn
x
Television
transmission
receiver
teletext
Datacast
receivers
Datocast
transmission
equipment
Off
-air
monitoring
C1
C2
C3
Control,
monitoring,
logging 8
biltin
C
Cz
Cj
Conditional access
equipment
Fig.4. Typical Datacast transmission system
Data length byte (DL). The DL byte is only

present if signalled by the t-r byte. The first
six bits are a binary number defining how
many' of the immediately following bytes
(including dummy bytes) constitute data for
delivery to the user. The last two bits are not
yet defined.
The DL byte is used when it is necessary to
send an incompletely filled packet in order
not to delay the transmission of data. Any
remaining bytes before the cyclic redundancy check are not defined but are still subject
to the CRC. A DL byte may be set to 0000 OOXX
(in transmission order) to keep a data service
open without sending data for delivery.
User data byte group. The remaining bytes

in the packet, excepting the last two, and
further limited by the DL byte when present,
and excluding any dummy bytes, constitute
the data carried for the users of that packet.
There are generally between 28 and 36 user
data bytes in a Datacast packet. There is no
restriction on the coding of the user data
bytes.
Byte transparency. Although there is no
restriction on the coding of the user data
bytes, it is, at present, necessary to eliminate
long strings of Os and is from the transmitted data to ensure that it is regenerated and
decoded reliably. If within any user data byte
group, taken together with any ci and DL
bytes, a sequence of eight consecutive 0000
0000 bytes or a sequence of eight consecutive 1111 1111 bytes occurs the broadcaster
will (except where there is no remaining byte
in the user data byte group) insert a following dummy byte which forms part of the CRC
but which is otherwise ignored by the decoder. The use of dummy bytes reduces the
length of the user data byte group, but only
in applications where complete bit -sequence
independence is required in the user data.
When the data is enciphered it is, in general,
very unlikely that such sequences will occur.
The function described above may later be
not required. It is therefore recommended
that decoders be equipped with a simple
method of disabling it at a later date.
Cyclic redundancy check (CRC). The last

two bytes of the Datacast packet are a 16 -bit
cyclic redundancy check on any ci and DL
bytes and all bytes of the user data group,
including dummy bytes. The data to be
checked, with bits in transmission order is,
in effect, applied to the circuit shown in Fig.
3, the register having previously been filled
with Os. The gates are modulo -2 adders
("exclusive-or"). When the feedback path is
disabled the basic 16 -bit CRC in transmission
bit -order is produced at the output.

It will be apparent that if the basic CRC is
appended to the input data, the process will
compare the calculated CRC with the incoming CRC and fill the register with 16 Os. This
indicates how real-time hardware can be
used to check the CRC, although it is currently more usual to conduct the operation in
software.
When the ci bit is set, and an explicit
continuity indicator is sent, the basic CRC is
sent. When the ci bit is not set, the eight -bit
continuity indicator is sent by modifying the
basic CRC. This modification is done at the
sending end in such a way that the above
comparison results in the register containing the eight -bit continuity indicator repeated twice, with the least significant bit at
the right-hand end of the bytes in the
register. A decoder can then extract the
continuity indicator from the CRC and use a
'flywheel' technique to allow it to interpret
the CRC correctly during occasional errors or
even during packet loss.
This use of a 16 -bit CRC in every Datacast
packet assures, with high confidence, that
any errors will be detected. The decoder will
be able to indicate whether data is right,
suspect or absent. The extent of the suspect
or absent data can be indicated and, where
packets are repeated, there is the possibility
of recovering some of it.
Over a year of practical experience with
Datacast transmissions shows that under
normal conditions fewer than one received
packet per million fails the CRC check. No
corrupted packet has yet been seen to pass
the CRC check.
DATACAST ORIGINATION
EQUIPMENT
Datacast can be added to a video signal at a

different point to teletext without any flow of
information between the two although, of
course, the same television line numbers in
any one field -blanking interval cannot be
used! Because there is sometimes a necessary redundancy in the normal teletext
output it would be more efficient to combine
the two in a device that recognizes this
redundancy, but this makes the operation
considerably more complex.
Figure 4 shows a block diagram of a
typical early use of Datacast, indicating the
broadcaster's area of responsibility. The
Datacast transmission equipment is a single
unit per network, with reserve available. The
reserve can be selected in such a way that
data in course of transmission is not lost.
The unit accepts inputs from six sources,
usually via modems over leased lines. Source
B is shown with conditional access equipment (encipherment, key distribution and
decoder addressing) used before the signal is
sent to the broadcaster and after it has been
received. Source C comprises three sub services, each with conditional access,
which are combined before sending to the
broadcaster along a single line. These sub services may have different addresses or they
may contain a sub -addressing facility within
the data carried by a service using a single
address.
The transmission equipment includes a
unit for monitoring the input data: in
particular it counts the number of user bytes
and packets being sent against time of day
together with measures of peak bit rate and
delay through the system. Off-air reception
can also usefully be analysed. This information is, of course, the raw material used in
charging the users of the service.
DATACAST RECEPTION
Because the data transport mechanism is

that of teletext, many of the existing teletext
chips can be used directly or adapted for
97
SPECIAL
Datacast reception. The BBC Design and

Equipment Department has produced a design which is being licensed to manufac-
DREH
turers.
Much of the development work on Data cast in the BBC has been done using the BBC
microcomputer together with its teletext
adapter as the receiving device.
ELECTRONICS
&
DATA SECURITY
Control and measurement

interfaces
Although it is possible to imagine freely

available services being broadcast by Data cast, the majority of the applications are
likely to be of a commercial nature where it
will be necessary to prevent a casual user
from understanding the message.
There are already techniques available for
enciphering data over a one-way telecommunications link and any of these may be
used on a Datacast channel. Methods of
embedding individual codes within decoders
in such a way that they can be uniquely
addressed, enabled and disabled have been
developed for direct broadcasting by satellite
and adapted for Datacast applications3.
BBC Research Department has developed
particular designs of equipment for Datacast
security. One provides data scrambling with
modest security without needing any extra
data signalling capacity. The other offers
greater security and allows control of individual decoders and the possibility of crediting charge units and then debiting them on a
pay-per -item basis.
Put your computer to work with

these versatile control and
measurement interfaces from
DCP Microdevelopments, described in the article on page 50.
Each Interpack offers a range
of useful i/o functions and can
be used with any of a number
of common micros: just add the
right intercard to match. For a
more complex system you can
link Interpacks together using
the special DCP Bus Intercard.
Order an Interpack together
with an appropriate Intercard
and you will also receive the
matching connectors at no
extra cost. Connector pack 1
- ---
Technical enquiries: ring 0480-830997.
1
1
1
Acknowledgement
The author wishes to thank the Director of
Engineering of the British Broadcasting Corporation for permission to offer this contribution.
1. BBC/IBA/BREMA,
September 1976, Broadcast
Teletext Specification
2. Chambers, J.P., 1986 "Datacast - auxiliary
services using teletext technology" IEE Conf.Publ.No. 268 International Broadcasting Convention
3. Bradshaw, D.J. and Wright, D.T., 1986
"BBC Datacast - conditional access operation",
September 1986, IERE Conf.Publ.No.70 Electronic Delivery of Data and Software
Further information about BBC 'Datacast can be

obtained from:
Head of Data Broadcasting,
BBC Enterprises Ltd.,
80 Wood Lane,
LONDON W12 OTT
telephone 01-576 0563
98
1
1
References
includes two port plugs and a

DPC Bus plug; connector pack
2 has ten 2mm plugs for other
inputs and outputs.
These special prices for
readers of E&WW include v.a.t.
and delivery within the UK.
Goods will normally be sent
within seven days, but if any
item is out of stock the
customer will be notified immediately of the estimated
delivery date. A v.a.t. invoice/
receipt
will
be
supplied
automatically.
This offer is available by
mail-order only, using the
coupon below, from the
following address:
Electronics & Wireless World Offer

DCP Microdevelopments Ltd,
2 Station Close,
Lingwood,
Norwich NR13 4AX.
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public service. It would be very easy to sell
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inefficiently and thereby deny access to
many small users whose modest needs cannot be met in any other way. The specification has been designed to support an almost
unlimited number of individually addressable services and it is hoped that means will
be provided for handling such uses without
undue technical and administrative overheads.
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IBM
NM
MINI
rCOMMUIVICATIONS
ler hand-held microphones with
coiled leads can be safely dropped
when both hands are needed.
Whichever way your sympathies fall, there is little doubt
that the revised Highway Code
could present a major problem to
the mobile radio industry.
Repair risks
Electrical and electronic dealers
have been expressing concern at
some of the proposals contained
in the White Paper (Cmnd 9712)
"Intellectual Property Rights and
Innovations" with a Bill promised for the next session of Parlia-
Cutting
ment. These include far-
reaching reform of the copyright

law including the legalisation of
the use of home video and audio
recorders (but with a 10 per cent
levy on blank audio tape), extending copyright to cover transmissions from distribution satellites etc. But the point that is
worrying the trade concerns the
special pattern parts found in
many appliances and equipments. In other words any components or fittings specially or
fittings specially designed for a
particular model.
It has long been common
practice when repairing appliances to buy spares from firms
other than the original manufacturer. This has been regarded
virtually as standard practice not
to be confused with deliberate
counterfeiting or "passing off'
doubtful equipment as coming
from well-known brand names.
But if the White Paper proposals become law, they give the
original maker and automatic
monopoly on all special pattern
parts for five years from the date
of manufacture and a right to
demand a royalty for another five
years.
What most worries the trade is
that the proposals include a right
to search premises and seize
goods allegedly in breach of contract, together with the possibility of imposing unlimited fines
and/or up to two years' imprisonment on conviction. What may
come to worry consumers is that
it seems to leave the way clear to
manufacturers to charge even
more exorbitantly than at present for their pattern spares and
so bring near the era of throwaway electronics as repairs become increasingly uneconomic.
Some American commentators believe that their own electronics industry will soon be
facing a crisis on the quality of
after -sales service they offer. As
W.H. Davidow, author of

"Marketing High Technology"
sky -waves
puts it: "Quality of service is
about to become the decisive
factor in corporate survival. The
cost of technical service on hightech products now runs an estimated one per cent per month.
That's nearly one-half the price
of the product in just four years
and that doesn't count the cost of
down time in lost productivity."
Actually his figure seems low in
comparison with often quoted
estimates of maintaining military communications equipment.
Over an operational lifetime this
can amount to anything up to
ten times the initial cost. But in
many fields the reputation of
firms, whether they realize it or
not, depends on their ability to
rectify faults quickly and at
reasonable costs.
answer or make a call, however

urgent."
This new Rule will, if
approved, clearly have a major
(ne is tempted to say devastating) effect on the current practices of the vast majority of cellular radio users and also most
other users of mobile two-way
mobile radio, including c.b.
operators and many radio
amateurs. Although the RSGB

has for many years recommended amateur radio driver/
operators not to use hand microphones or double headphones,
the majority of mobile transceivers are sold with hand microphones.
The Highwy Code, issued
under the Road Traffic Act, sets
out rules for safety on the road.
The Secretary of State is empowered to revise the code from
time to time in such a manner as
he thinks fit, subject to the
A few months ago one began to approval of Parliament. Failure
he
strong rumours that the to observe a provision of the code
Department of Transport, which does not, of itself, render a performs part of the enormous De- son liable to criminal proceedpartment of the Environment, ings but a failure to observe it
was planning to introduce into a may be used in either criminal or
revised Highway Code a new civil proceedings to establish
recommendation aimed at driv- liability.
The possible driving hazards
ers using hand-held microphones and telephone hand- represented by use of the relatively large and bulky handsets
sets while driving.
It has recently been confirmed currently provided for virtually
that the draft revision of the all models of cellular and many
Highway Code, currently before other radiophones has been
Parliament, has a new "Rule 49a noted before the "Communica- Do not use a hand-held tions Commentary", as has the
microphone or telephone hand- curious anomally that a driver
set while your vehicle is moving, seen using an electric razor
except in an emergency. You while driving is liable to prosecushould only speak into a fixed, tion, but the basically similar act
neckslung or clipped -on mic- of using a hand-held microphone
rophone when it would not dis- does not constitute an offence.
tract your attention from the On the other hand it has been
road. Do not stop on the hard pointed out that one -arm drivers
shoulder of a motorway to are permitted and that the smal-
Mobile safety
In the medium -waveband, it is

well recognised that the service
area of broadcast stations tends
to decrease dramatically between

the approach of dusk until some
time after dawn when the D -layer
regains its capacity to absorb
signals. Service areas, these
days, c.re almost invariably li-
mited by interference rather

than signal strength. Apart from
the few very high -power stations
used for external broadcasting or
which attempt to provide national coverage by blasting their way
through co -channel interference, the absence of an effective
D -layer after dark and the consquent reflection of the skywave
signals is regarded as a hindrance rather than a help. What
most a.m. broadcasters would
like is an antenna that would
radiate maximum vertically
polarized ground -wave signals,
minimum -possible skywave
signal.
The conventional mast -
radiator unfortunately radiates

only about 15 per cent of its
energy along the ground, nearly
85 per cent is radiated above the
horizon, representing lost power
in daylight and unwanted interference t listeners hundreds
of miles away at night.
The American National Association of Broadcasters, urged on
by their medium -wave broadcasters who have been steadily losing audiences to their f.m. rivals
and also by the FCC which would
like to see a revival of interest in
medium -wave broadcasting
which will soon extend in Region
2 up to 1705 kHz instead of 1605
kHz, is now planning a trial of
two new experimental antenna
systems designed to put more
power along the ground, less
towards the sky.
Experimental antennas are expected to be field tested in Lees -
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HAMEG OSCILLOSCOPE 605 D'-a' T,ace 60MHr
Delay Sweep Component Teste
HAMEG OSCILLOSCOPE 203 E D.a Teace 20MHz
Component Tester role lwop,oDes
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BLACK STAR COUNTER TIMERS aSt 51

APOLLO 10100A1Hz RaooPea,.1 Tow lnlewa Et(
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110 WYKEHAM ROAD, READING, BERKS RG6 1PL
AM
Callers welcome 9am to 5.30pm. MON-FRI. (UNTIL 8pm. THURS)

100
3.00
WE HAVE A
LARGE STOCK OF
2716 EPROMS
FOR SALE
PRICE ON
APPLICATION
+10%.
ONLY A FEW LEFT

SPECIAL PRICE 295.00
inc vat & carr.
E.H.T. TRANSFORMERS
High-grade E.H.T. Tranny.
PRI 240V, sec. 10,000V, 18
M/A.
Probably used
for
boiler ignition but with 101
other uses!!! 5 inc. carr &
VAT.
31/4'
Brand
redundant
or
surplus
stock.
Best prices paid. Any
amounts
considered.
Test
equipment
also
tendered for.
CONSTANT VOLTAGE
TRANSFORMERS
meg
drives.
TWIN 8 DISK DRIVES

Brand
New
Magnetic
Peripherals with PSU ring
for details ONLY 100 inc
vat & carr.
Let us tender for your
By Famous Maker. 3KVA.

A very sturdy unit size 270
x 240 x 500mm these units
will
control
the
mains
fluctuations from -20% to
Output 220 or 240v + or
10
New 150.00
DAVID Jnr II control card.
100.00.
Both
these
items
are
offered at a fraction of their
cost.
Please ring for details.
inc
.,Maie,
STEWART OF READING Telephone: 073468041

ma
Winchester
base bolt fixing

vat & carr.
285
Melee
RODIME
HIGH GRADE
CAPACITORS
22000mfd @ 63vdc
33.5a
ripple
current
complete
with
mounting
clip size 105mm x 65mm
4.95 inc vat & carr.
No 2 22000mfd @ vdc
screw terminals with single
No
C219
w,
mimeHUNG
RAGA.
ai
v:,Mllaei
GRUNOK.CQOUR GENERATOR 1 Get
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40419 6M..
MARCONI Rry4ANOL115ETCRTr2603 Semi

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No
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Leo TRANSISIOR'E56RMe.
HIGH GRADE
TRANSFORMERS
30.0.30v @ 4a 8v 2a
No 2 26.0.26v @ 3a 8v
No 3 22.0.22v @ 2a 8v 2a
9.00 inc vat & carr
tn..",
01200
,CEE B
AT COMPETITIVE PRICES
SCR ENWre"3R5 wine a RSV

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24
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GENERATORS
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01-262 5125 & 01-723 7851

WE WILL MANUFACTURE PROTOTYPE
OR PRODUCTION RUN TRANSFORMERS
t.5
Core. ve. Newa
ALeyw.30eryea Conpee.er
e,.,,m.9er
GREEN
jMERT,.f,B.aR_
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9-10 Chapel Street, Marylebone

London NW1 5DN
rep. .'e
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Ca,
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wORenKe OR -FR
Mar, ,rw- 1
crece rase
Rem 6
0310
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Tr.
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MULTIMETERS
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06.f00
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OSCILLOSCOPES
Is
36Nw.rlow,
f1reIRA17L530Rn,
l0MHz Dual Trace Delay Sweep. With manual

ONLY [476 each
I,w
FURTHER DETAILS
COMMUNICATION RECEIVERS
Tektronix 2215 Oscilloscope
TEKTRONn5110.FVETRACER
TEKIROMA405Du Dese MOON Om, Seem
ltET*3666 .460 SS
is Ow., S..
85 FOR
Precision made Swiss D.C.

motor running on -9v dc
these motors have a 70:1
gearbox and are extremely
powerful. Size 26mm x
45mm 3mm output shaft.
Normal cost over 20 our
price 4.95 inc VAT &
postage.
CIRCLE
100 FOR
15 AMP ISOLATION
TRANSFORMERS BY
FAMOUS MAKERS
These
high
transformers
are as new and
were
manufactured for a top U.K.
electronics
company
to
extremely high standards.
Each transformer has a
large range of tappings for
adjusting
inputs
and
outputs.
Size approx 37kgs. Our
price 95 inc. VAT. Ring
For Carriage Details.
GOULD/FARNELL
15amp
switch
13.8v
mode
P.S.U.s. These robust and

versatile
supplies
will
power up radio amateur
equipment nicely.
55 inc vat post.
GOULD
ADVANCE
5v
60amp
switch
mode
P.S.U.s 45 inc vat carr.
19v 15amp switch mode
P.S.U.s 45 inc vat carr.
FANS
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9.50
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L.T. TRANSFORMERS
Parmeko Atlantic Series
potted type. Pri 220-240v.
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The
following voltages can be
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2-4-6-8-12-14-2836-40-42-44-48v @ 1.6A
conservatively rated 7.50
inc VAT & carr.
FURTHER DETAILS
amateurs currently operating on

the band are in favour. Almost
everyone agrees that the amount
of operation on the band is at a
level far below the crowded 7 and
14 MHz assignments, even
though radio propagation characteristics of 10 MHz are well
suited to the present sunspot minimum period.
Reasons for the low activity
include the fact that transceivers
and transmitters of the 1970's or
before made no provision for
either reception or transmission
on this band; that many popular
transmitting antennas are not
suitable for 10 MHz; that the
majority of h.f. operators prefer
s.s.b. to c.w., yet have no wish to
flout the RSGB/IARU recommendations; and that the number, strength and modes of the
many high-powered fixed stations (by no means all of them
registered with the International
Frequency Registration Board)
active for many hours each deay
reduce the usable frequencies to
international smuggling of just a few narrow gaps for most of
the time.
drugs.
Recently, after an interval of
three years, I have been spending
some time on this band using a
c.w. transmitter with the relatively low output power of 15 to
form of a home The ITU World Administration 20 watts in the
"Mark
a
paramilitary
v.f.o.,
built
1979,
Radio Conference of
of the
among its many recommenda- 123" valve transmitter
random
tions affecting amateur radio, 1955 to 1970s era and a
formally allocated 10,100 to length long-wire antenna passing through the roof space to a
10,150 kHz to the amateur service on a secondary basis, with tree in the garden.
Despite the low power and low
the fixed (point-to-point) service
remaining the primary user. activity it has proved surprisingAlthough most frequency ly easy to contact stations in
changes above 10 MHz were sub- most European countries (Rusject to a "transfer" period of five sian amateurs are apparently not
years from July 1, 1984 (below 10 yet permitted to use the band)
MHz the transfer period is ten although the skip distance, even
years) for changes not involving at noon, is seldom much below
transfers, the operative date for 500 miles. Low -power signals
the new regulations was January near the m.u.f. tend to build-up
or fade-out very rapidly as the
1, 1982.
The Home Office, then in boundary of the dead zone
charge of the Radio Regulatory fluctuates. When conditions are
Division, was one of the first favourable, long-distance transnational administrations to con- missions come through well.
But there remain long periods
firm that amateurs were free to
few, if any, amateur signals
when
segment
narrow
in
this
operate
from January 1982. Because the can be heard. For much of the
band was so narrow and time the high -power commercial
41:ateurs were only the secon- stations occupy about 40 of the
dary users on a non-interference available 50 kilohertz. With
basis, the RSGB and later the some exceptions the amateur opIARU recommended that opera- eration is largely confined to
tion should be confined to the frequencies below RMP, a Soviet
narrow band modes of c.w. and Navy coast station in Kaliningrad
r.t.t.y. This recommendation, on 10,118 kHz. This uses c.w.,
which is non -mandatory, has but most of the others send
been the subject of considerable streams of multiplexed r.t.t.y. or
controversy in the UK, Australia, facsimile signals that spread over
South Africa, although it is evi- several kilohertz. Band -sharing
dent that most of the relatively between low -power and high small number of British power services seems more suc-
camels being undertaken by Sydney University's School of Biological Studies is using American by Richard Biby will have a series
of short vertical radiators placed made radio -tracking collars.
around the base of a convention- These carry both a small v.h.f.
transmitter which can be tracked
al monopole antenna. The theory
directly over distances of 20-25
is that with correct phase and
amplitude distribution the short km and a one -watt transmitter
elements will increase ground - that is received on low -orbiting
wave radiation while cancelling weather satellites. The data is
recovered and processed in
out much of the skywave.
France, from where it can be
The Beltsville installation,
communicated and displayed on
based on a design by Ogden
Prestholdt, will use a combina- the screen of a personal compution of vertical, horizontal and ter in Sydney.
Similar tracking collars have
diagonal elements to accomplish
been used to track
previously
pattern.
radiation
a similar
Provided that FCC and FAA polar bear and caribou in the
as too
approve the trials, it is expected Arctic, but are regarded
the new antennas will take a year heavy for that other Australian
to build, followed by a year of bilogical curiosity, the kangaroo.
of
field trials. There has been sur- But is also raises the question
as
tracking,
satellite
whether
work
prisingly little fundamental
trackon medium -wave antenna design well the established v.h.f.
a pracsince the classic work on direc- ing "bugs", is becoming
tional antennas by Dr George tical possibility for long-range,
secret surveillance of suspect
Brown of RCA in the 1930s.
motor vehicles or vessels suspected of being engaged in the
burg, Virginia and Beltsville,

Maryland. At Leesburg, a design
Using 10.1
MHz
Camel mobiles
as a surprise to
learn that Australia has the
largest number of wild camels in
the world, the result of bringing
in camels from the Middle East
in the nineteenth century to
provide transport in the dry interior regions of that vast country. Today, numbers of feral
camels roam wild in several regions of Australia with even a
flourishing business in exporting
the sturdy Australian camels to
the Middle East for racing and
breeding.
According to Electronics Australia a current study of the feral
It always comes
cessful on the 3.5 MHz band

where the gaps are (usually)
wider.
In brief
The first Japanese amateur radio
satellite, JAS -1, now renamed
"Fuji" was launched successfully
on August 12 on a Japanese H-1
launch vehicle along with two
other satellites.
The 1987 RSGB National
Amateur Radio Convention is to
be held at the National Exhibition Centre near Birmingham on
March 28 and 29.
EMC problems
The increasing concern with
electromagnetic compatibility
e.m.c. which now affects virtually all forms of communciations
and electronic equipment practice is well illustrated in the
range of the papers due to be
presented at the IERE conference at York before these notes
appear. The term e.m.c. is taken
to cover such diverse topics as
the potential biological and
ignitition hazards of non -ionized
electromagnetic radiation; com-
patibility between v.h.f./f.m.

broadcasting and the aeronautical service in the adjacent band of
108 to about 118 MHz; problems
of harmonic radiation from microwave ovens (something that
may well prove a major problem
when 12 GHz DBS begins); interference arising from the inter -
modulation products at
multiple -transmitter sites, etc.

One of the first services to
experience serious e.m.c. problems was the amateur radio service which began to encounter
tv -interference situations as
soon as Alexandra Palace opened
its 405 -line tv service exactly 50
years ago on November 2, 1936.
Then it was found that the third harmonic from 14 MHz transmitters would need much more
attentuation by shielding and
filtering than had even previously been found necessary.
Techniques to overcome interference to v.h.f. television
were however successfully developed well before the change to
u.h.f. tv brought at least temporary relief from the relatively few
remaining cases of interference
to valve-type receivers. Unfortunately the widespread introduction of solid-state devices (particularly r.f.-susceptible c.m.o.$)
into so many domestic appliances, combines with the
phasing out last year of the free
assistance to viewers and listeners previously given by the DTI's
Radio Investigation Service, has
101
RAEDEK ELECTRONICS
Tel: 021-474 6000
Telex No: 312242
SERVING THE COMMUNICATIONS AND ELECTRONICS INDUSTRIES
MIDTLX G.
102 PRIORY ROAD, SCRIBERS LANE, HALL GREEN, BIRMINGHAM B28 OTB. ENGLAND.
TRANSISTORS:
TYPE:
LIST:
2N3375
2N3553
2N3632
2N3733
2N3866
2N4416
2N4427
2N5090
2N5109
2N5160
2N5589
2N5590
2N5591
2N5641
2N5642
2N5643
2N5913
2N5944
2N5945
2N5946
2N6080
2N6081
2N6082
2N6083
2N6084
2SC1729
2SC1945
2SC1946A
2SC1947
2SC1969
2SC1970
2SC1971
2SC1972
10.90
1.60
12.95
12.95
1.20
0.75
1.40
10.90
1.95
3.00
7.60
7.90
9.50
6.95
9.30
11.85
2.50
7.85
10.10
10.80
6.65
8.40
10.50
11.20
12.00
12.50
3.45
16.00
8.50
1.80
1.40
3.50
9.50
VALVES:
TYPE:
2SC1978
2SC2053
2SC2237
2SC2287
2SC2290
MRF240
MRF245
MRF247
MRF433
MRF449A
MRF450
MRF450A
MRF454
MRF454A
MRF455
MRF458
MRF475
MRF476
MRF644
MRF646
MRF648
MRF901
SD1013
SD1019-STUD
SD1019-5
SD1127
SD1134-1
SD1136
SD1143
SD1219
SD1272
SD1278
LIST:
TYPE:
LIST:
TYPE:
6.40
0.80
6.00
9.60
20.00
20.70
33.00
33.30
9.00
10.15
11.50
13.80
17.25
17.25
16.50
17.20
2.30
2.15
22.50
27.00
32.70
2.75
9.75
23.10
22.80
3.10
2.25
11.90
9.40
14.70
10.95
13.75
AH211A
AH2511
AH2532
BT5
BTSB
BT17
BT17A
BT95
C3J
C3JA
E55L
E80CC
137.50
90.00
31.50
52.50
52.50
142.00
130.00
125.00
30.00
30.00
56.00
14.00
21.00
3.90
7.50
21.25
EF94
EF95
EF183
EF184
EK90
EL34
EL36
E8OL
E88CC
E9OCC
E130L
EB91
EBC91
2.00
2.00
2.00
1.50
00V02-6
00V03-10
QV03-12
2.30
1.90
1.60
1.70
3.00
2.30
2.30
2.95
2.20
EF92
EF93
SOLID STATE RECTIFIERS

RECTIFIER VALVES
OSCILLATOR VALVES
COOLING FANS/FILTERS
ML8741
NL SERIES
1.65
1.80
EF91
INCL.
CERAMIC CAPACITORS
VACUUM CAPACITORS
GRID LAMPS
CARBON FREE HOSE
WATER FLOW SWITCHES
1.60
1.85
ECC88
ECC91
ECC189
ECF80
ECF86
ECF801
ECH81
ECL82
ECL86
EF80
EF85
EF86
EF89
INDUCTION AND DIELECTRIC HEATING SPARES
GZ34
KT66
KT77
KT88
ML8536
QY3-65
QY3-125
QY4-250
RG1-240A
RG4-3000
XG1-2500
XG5-500
XR1-3200
XR1-6400
OA2
1.50
TYPE:
LIST:
TYPE:
OA3
2.50
2.50
2.50
2.50
39.90
42.00
6AU5GT
6AZ8
6BA6
6BE6
6BH6
68J6
6BK4C
6BN8
6BZ6
3.70
3.80
6C4
6CB6A
6CJ3
1.95
1.80
0B2
1.90
1.80
EL86
EL519
EL803S
EL821
EN32
EN91
EZ80
EZ81
EZ90
FG17
FG105
GXU1
GXU4
3.25
1.60
1.60
ECCB5
2.00
1.60
ELM
1.35
1.10
1.35
1.25
EBF89
EC90
ECC32
ECC81
ECC82
ECC83
LIST:
OB3
OC3
2C39A
2C39WA
1.40
3.90
2.30
1.60
2.10
7.70
9.95
13.75
16.25
2.00
1.60
1.50
1.50
24.50
160.00
15.00
45.00
2.10
9.00
8.75
24.95
275.00
265.00
2D21
2E26
2K25
3-400Z
3-5002
3B28
3C45
3CX100A5
4-65A
4-125A
4-250A
4-400A
4-400B
4-400C
4832
4C35A
4CX250B
EIM AMP
4CX250B
NAT
4CX350A
4X150A
5AR4
5AS4A
5R4GYA-B
5U4GB
5V4GA
6AH6
6AK5W
6AK6
6AL5W
6AQ5A
6AQ5W
6AS6
6AS7G
22.00
5.30
7.00
57.50
63.00
69.80
10.00
90.00
52.50
24.50
72.50
120.00
2.00
200
7.50
114.00
78.00
85.00
15.00
24.50
35.00
52.50
60.00
76.00
80.00
80.00
80.00
30.50
135.00
55.00
48.00
87.00
33.70
2.10
2.10
3.50
2.10
2.50
2.30
2.50
1.95
1.80
1.75
1.80
2.40
4.30
CIRCLE
59 FOR
FIELD ELECTRIC LTD.
SILICONE GREASE
1.00
1.25
EK7
6K11
6KD6
6KD8
6L6GC
6LQ6
6011
6SL7GT
6SN7GTB
6U8A
12AT6
12AU6
12AV6
12BA6
12BA7
30.00
18.00
41.20
4.80
4.80
81.00
95.00
24.50
52.50
2.95
140.00
6.15
2.20
32.00
24.50
9.00
9.00
4.95
7.25
8.70
3.95
6.50
4.20
3.20
26.00
12.20
11.50
35.00
4.65
48.00
53.00
101.00
55.00
6.50
52.00
2.90
75.00
36.85
5991
2.00
1.80
2.35
2.00
2.70
3.70
3.75
12BY7A
12BZ6
12DW7
LIST:
813
934
935
2050
2050A
5544
5545
5557
5559
5727
5867A
5879
5965
6130
6146A
6146B
6360A
6550A
68838
6973
7027A
7199
7247
7262A
7360
7586
7587
7591A
7815AL-GE
7815R
8122
8906AL
150B2
5728
807
810
812A
1.50
1.70
1213E6
TYPE:
WE ALSO SUPPLY
EIMAC TUBES AND

ACCESSORIES
PRICES- CORRECT AT TIME

OF GOING TO PRESS
- 1.50
TERMS
- PLEASE ADD 1.00
P&P AND VAT
r,i
15% to orders
URTHER DETAILS
HIGH QUALITY
Am
3 Shenley Road, Borehamwood, Herts WD61AA. 01-953 6009
2.30
6.30
2.45
4.20
2.25
2.50
4.25
3.95
4.20
6.25
4.70
2.50
2.25
5.90
2.00
3.90
6.25
2.25
2.25
3.05
2.00
6GK6
6HF5
6HS6
6JB6A
6JE6C
6JS6C
LARGE RANGE OF SOLDERING IRONS AND ACCESSORIES

P
2.15
2.00
4.50
3.50
2.50
6E5
6EA8
HEATSINK COMP. (100g)- 1.50
CONTACT CLEANER
FREEZE IT AEROSOL
etc etc.
1.50
1.95
6CW4
6DC6
1000's of VALVES/TRANSISTORS/IC's IN STOCK. PLEASE ENQUIRE ON TYPES NOT LISTED.
SERVICE AIDS
LIST:
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Official Orders/Overseas Enquiries Welcome/Telephone Orders Accepted.

Open 5 days. 9am/5pm. Please ring for C/P details not shown. All test
equipment carries warranty. All prices inc. 15% VAT unless stated.
TRANSFORMERS ALL 240V PRIM.
12-0-12V 2A x
23.50inc
C/P
6-04V 20A 23.00 me CIP

9-0.9V
to C2.75 inc
Woden 11V 80A
C/P
(42.00 inc
C/P
SPECIAL OFFERS
POWER SUPPLIES 240V INPUT
Quantum (Winchester) 8"

Fixed Hard Disk Drive. 10
Meg = 240V New
ont Boxed with
E
Data. 0200075.00 inc
Date
VAT and C/P
PC Card P.S.U. 240V/115V Input New 5V

IA Regulated 107.100 7.50 inc C/P
Vide'. 6
Digit LC .D.
Displays New with rnnn9
Fac a Mounted on P. C.
c/w 12 Keyboard Rocke
Woden 27V 30A GP Please Ring
7.6V 120A 40.00 C/P Please Ring
ithes I4Stockin
Rocker 4x4 Stack Led
S
22.000f 25V NEW 1.75 Computer

Grade Caps inc C/P
Display. Mun Colo

2
S eedblo
40
Way inc
Jumper Leads
ds. 6.95
C/P + Data
811 Waterproof
rproof Speaker Unit 12.50
C/P 250
BardiclChloride Safety Handlam p c/c

Sealed Alkaline Ben = Charter Pack
24V DC Input New 38.75 inc GP
BuRender
lgir
NCR Micro -Fiche 390 x 279. 189mm

New Portable 240V AC 24/12DC Input
75.00 inc C/P
3.50 inc C/P
Marconi TF144H Signal Generator 10

KC/72MHz 195.O0 C/P Please Ring
C12.95
250V 6A
EC Filter Plug Units
Chassiswith
Mount
l
Epo
Sibate P3 Dust Level Meter 50.00
Wavelek 142 HF Voltage Controlled

Gen
Wavetek Vonage Controlled Generator
11I 225.00
Wier 403 0-30V 0-34 P. S.U. 69.00
C/P Please Ring
4K 8Bits Ne
in Plastic Box
100 75
Inc GP
40mm 3.50
Boxed with Dala
46.00 in
GP
125.00
19.95 C/P 2 75
COPPER CLAD BOARD
4.51f65
1
rSN02178x26.No254.177,
5150
24
discount.
Double Sided New Inc C/P 508.380.3 Nob

7.50.457x305.3 No 7 7.50. 380.254.3
No85.75. Quantity= discount. All boards
are epoxy glass.
Farnell Switch
SOOM/A
CIRCLE
Century Way. March. Cambs. PE1580W Tel' (0354)51289
Lambda Metered P.S.U. 0-4V 0-1A x 2
Quantity
enschein 4200 D
Batts: New 8 Boxed 12V
DC 5 7Ah ABS Case
C16.95 inc C/P
For further details Contact
HARRISON ELECTRONICS
Data Recording Fan Cooled Linear P.S.0

15V 15V 8A x 2 New 30.00
Plastic Boxes 760

100.40mm. 6 for 5.00
inc C/P
SonnDot
4+11 GHz SATELLITE TV RECEIVING EQUIPMENT

RECEIVERS, LNB's, LNC's, FEED HORNS,
ANTENNAS, ANTENNA POSITIONERS,
POLOROTORS, LINE AMPLIFIERS, ETC.
Gould 24V 15A Switch Mode. New 8 Boxed

Data 215.72 x 89 57.50 C/P 2.75
Single Sided New Inc C/P

508.380.3 No 7.00. 457.305.3 No 2
12V DC 23RPM 1.2 Watt

Permanent Magnet DC
Motor with Integral
Gearbox 6.00 inc C/P
Farnell Fan Cooled P.S.U. Switch Mode +5V

104.5V IA + 12V 3A -12V 1A 28.00 C/P
2.75
AC DC 24V 4.8A Linear P S.U. New& Boxed
227.123.70 19.95 GP 3.50
12V DC Audible Warning

Device Single Tone sow
State 1.95 inc GP
Acos Sourd Level Meter 90.00

C/P 5.00
102
near
15-16V 1 0A
PPlant Ups
G
Coulant Linear P.S. U. New Boxed 6V 7A
Stepper Motors 4.5V 1.44

2 Deg Step Sanyo Step:
Si',, 8.50'
C/P
Croydon PW2 Wherstone Bridge

11Y5.00 C/P 5.00
Gould Type 3795V 40A -12V 4A +15V 11A

Switch Mode 60.00 inc C/P
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Marconi VSWR Amp =MKln 375.00
Hewlett Packard 301 Pen Recorder

125.00 Portable Case Type
Gould PM A47 12V 3A Linear P.S.O. 15.00

GP 2.75
700.00 Buyer Colleur
Bulgin Pointer Knobs

Black Plastic with Metal
B shG bS e F Se
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Comark RPM Meter 75.00 C/P Please

Ring
Farnell G -65M 6V 5A Switch Mode

145.88.33 20.00 C/P 1.75
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750M/A 17.25 GP 2.75
Lambda Linear P.S.U. 20V 5.2A 225.120.
65mm 25.00 C/P 2.75
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Alfred Spec -Ana H zer MF5/AL2

20HU35KHz 590.00
Surgger
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Please Ring
er
Voitex Co. + 12V 1.5A

+SV 30A -12V 10A
Linear P.S
240V
17x
x
25.00 0 GPP 5.00
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0/10MHz 89.00 C/P Please Ring
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Please Ring
Mains
p C.B. 9 x 2532JL 45
Gould Switch Mode 5V 204 603 0870 105 mm

14.95 C/P 2.75
Mode+5104 +24V4A +12V
-5V 1A. New
inc C/P
Ex -Equip. Data
Gould 5V 604 Swilch Mode

12.50 C/P 3.50
27.75
320.1250
142
Ali -Die Cast Boxes 114 c 64.30mm 2.50 inc

C/P
P
te Mecs
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&
WIRELESS WORLD
Editorial Feature List

DECEMBER
Enclosures
There is
a vast range of boxes, racks and enclosures of all kinds in

which designers can house their equipment.
If you have no house style requirement and can use a 'reach-me-down'
case, our December feature will help you make a choice.
WarningDCwith
ce 2
Control Electronics. Dot Matrix Head with 12V

DC Geared Motor Chain Drives etc. Approx
Dia 11 x 121/2.71/2 15.95 inc C/P
FOR FURTHER DETAILS
ELECTRONICS
For further advertising details please ring
Ashley Wallis on: 661 8641
put e.m.c. back as a major concern to UK amateurs. This has

been raised still further by the
DTI threat to introduce variations to the licence in respect of
Changeover
switch
ac conversion
equipment145kVAI
d.c.
Battery
controller
-CD--`"63")Thr
Private
power and frequency bands in

dwellings
really difficult cases.
Battery
The RSGB has announced a
charger
Solar cell modules
"11 -point plan of action" to comDiesel
ISOkWpI
bat e.m.c. problems, though one
Well
generator
that
several
pumpsr+.
feeling
help
cannot
1
of the proposals including the
;
"code
formal
of
a
establishment
Street
.
.
of practice" and changes to the
lights
Amateurs'
Radio
the
syllabus of
System
T
Alarm
controller
Examination could well cause
.
controversy. The society also has
T
the ambitious plans of estabBatteries
Data
lishing a database listing case
1300kWh)
logger
histories for all known radio and
Undersea
cable
television receiver models. It is
D'
-0
also going to have a job to conT
Existing
prickly
vince some of its more
Other
diesel generators:
loads
members that very few amateurs
300kWx3
can expect to be lucky enough to
320kWx1
500k W xl
be able to run 400 watts (p.e.p.)
into a high -gain 144 MHz antenna located just a few feet away with a normal mains -powered up. A 45 kVA d.c./a.c. solid-state ware." Viewers had little difficulfrom the neighbour's tv antenna relay; this was particularly the conversion equipment is self - ty in identifying this message as a
without causing some interfer- case with a mechanical wind - commutated and of the pulse - protest at the introduction of
ence.
generator while the large bank of width modulated type. The sys- encryption on the premium HBO
storage batteries also needed tem is designed for automatic, film channel coupled with the
increase in fees.
unattended operation.
considerable attention.
Until encryption, it had been
A parallel d.c. connection with
Work on medium -power
that about 1.5 -million
estimated
the
howreduces
generator
diesel
generators,
the
photovoltaic
ever, continues elsewhere in- time during which the diesel viewers using their own C -band
tended primarily for remote runs when the reserve battery (4 GHz) satellite receiving terareas enjoying more and stron- power falls. With a parallel a.c. minals were watching HBO free.
subFive or six years ago interest ger sunshine that the UK. Under connection the diesel, once trip- The encryption of HBO and
began to grow in Europe, the a Japanese government -funded ped on due to extended overcast sequently some of the other preor rainy weather conditions, mium film channels decimated,
USA and Japan on the use of solar "Sunshine Project" considerable
power or, alternatively, hybrid efforts have been made for sever- would run until the battery is at least temporarily, the sales of
large-dish home satellite rewind/sun generators as natural al years to increase practical uti- fully charged.
Monocrystalline silicon solar - ceivers. The USA has had no
energy sources for such applica- lization of solar energy for elections as terrestrial broadcasting tric power generation by de- cell modules each have a nomin- Ku -band (11 GHz) DBS since
and communications. It has al- veloping lower -cost, higher - al output of 52 watts peak (22.4V, 1984.
The intrusion of Captain Mid2.32A d.c.) under standard conways been more difficult and efficiency solar cell modules.
One such project has involved ditions (1 kW/m2, 28C, 1.5 air night's message into the Galaxy 1
more costly to generate electricity than to convert an existing the use of a large array of solar mass). The modules are series - distribution satellite transponmodules, capable of about 50 kW connected in groups of 15, with der sparked off deep and widesupply into r.f. power.
spread concern among the cable
Following experiments by the peak output, to provide an elec- 65 such circuits in parallel.
programme providers and the
A description of the system in
French broadcasters, both the tric power supply for the small
users of satellites for private or
Ryuku
Electric
journal
in
the
Mitsubishi
Zamami
the
IBA and BBC mounted pilot ex- island of
periments, with UK weather con- Islands. Since October 1985 an "Advance" (June 1986) suggests business communications. Was
ditions favouring the hybrid prototype system developed by that the operational prototype it possible that anyone equipped
wind/sun systems. For a couple Mitsubishi Electric has been sup- will lead to systems providing with a dish and a medium or
of years the IBA kept a small plying power to 14 private dwell- greater supply stability, lower high -power microwave transfour-channel television relay sta- ings, well pumps and other energy consumption and im- mitter could play havoc with a
tion at Bossiney, on the north loads. Normally the many small proved resistance to and greater satellite with little fear of being
coast of Cornwall and serving and remote Japanese islands use safety under the environmental caught?
However, this has proved to be
about 300 viewers, on the air in small- or medium -power diesel extremes found in these islands.
a challenge to which the FCC,
this way. It was hoped that such a generators with the disadvanworking with field agents of the
system might prove economical- tages of substantial initial and
Federal Bureau of Investigation,
running costs, comparatively
ly attractive at sites remote from
has
often
proved equal. On July 22, it
and
maintenance
heavy
the public supply main, although
was formally announced that
in practice the Bossiney site was uncertain transport and de"Captain Midnight" had been
liveries.
connected to the public supply.
identified as a John MacDougall
In the prototype system, solar In April this year, a written mesAlthough the system provided
a
miten
of Oscala, Florida. He had used
charge
for
about
to
used
appeared
are
sage
modules
the amount of power it was de- cell
signed to give and with the aid of bank of 136 tubular-type lead - nutes on the American "Home for the purpose not a private
large storage batteries was able acid batteries with a total storage Box Office" satellite -distributed up -link but the facility of the
Central Florida Teleport where
to keep the station running suc- capacity of 305 kWh and able to cable tv channel: "Good evening
he "moonlights" as a technician.
reMidnight.
day's
Captain
one
from
HBO
roughly
provide
the
found
that
cessfully, it was
system required a considerable serve of power. An existing diesel $12.95 a month? No way!
PAT HAWKER, G3VA
maintenance effort compared generator is available as a back Showtime/Movie Channel be-
r'-
r -r -
---
Solar power
growing
Midnight
hi -jack
103
IT'S YOUR CHOICEIX.
QUICKPAD
The low cost solution to PCB design
contact us now for full information
Conguin Software Limited
Freepost, Morden, Surrey SM4 1 BR Telephone: 01-640 9130
ELECTRONICS
&
WIRELESS WORLD
Editorial Feature List
JANUARY 1987
Printed -Circuit board connectors. We look at the morass of

types that are used to connect printed circuits to backplanes, to
each other, to flat cables and to the outside world.
FEBRUARY 1987
Instrument read-outs. Numerical displays are now used on
the humblest of equipments. This feature examines the

characteristics of liquid -crystals, fluorescent, plasma and other
types and lists those available.
MARCH 1987
Production soldering and re -working equipment, with

reference to the techniques used in the surface mounting of
components. We include all types from the ordinary soldering
iron to flow -soldering machines.
APRIL 1987
Spectrum analysers. Advances
in the application of
microprocessors to these instruments have opened up a wider
area of use. Those on the UK market are listed and new
techniques examined.
For further advertising details please ring Ashley Wallis on: 661 8641
101
BOOKS
32 -bit Microprocessors, ed. L.J.
Mitchell (CAP Scientific Ltd).
Collins, 248 pages, hard covers,
25. Details of current and fu-
Introduction to
ture devices, including the

68020, Z8000, 80386, the Inmos
Transputer, AT&T's WE32100;
plus an examination of RISC
architectures.
Modern Relay Technology, ed.

Hans Sauer, 2nd edition, SDSRelais Ltd (17 Potters Lane, Kiln
Farm, Milton Keynes MK11
3HF), 357 pages, hard covers,
single copies free of charge to
engineers and students. Encyclopaedic handbook of relay
know-how, from A for Absolute
Dielectric Constant to Y for
Yoke. No sign of a commercial
message, not even in the tables of
relays on the market, to which
other manufacturers have generously been invited to contribute.
There is an interesting applications section with many detailed
examples and a glossary of 665
technical terms and phrases with
their equivalents in French, German and Italian. Would you have
known that "organe de commande d'excitation" translates as
Introduction to Data Communications and LAN Technology, by Ed da Silva (of the Open
University). Collins, 159 pages,
soft covers, 14.95. How the
Antennas and Signal Distribution System, by M.J. Salvati. Pitman Publishing (Howard
TV
RECOGNITION
TE.1 pMIINDNPl1CH1UL
E
"processing unit"?
Confidential Frequency List, by
Oliver P. Ferrell, 6th edition.
Duckworth (Gilfer Associates
Inc.), 336 pages, soft covers,
12.95. Frequency -by -frequency
directory of the h.f. spectrum
from 4MHz to 28MHz, excluding
only the broadcast bands, compiled from ITU lists and from
observations by monitors in both
the US and Europe. Entries, a
proportion of them inevitably
incomplete, include news agencies, weather stations, naval, airtraffic control, diplomatic, and of
course spook stuff. There is
Ed da Silva
much to intrigue the curious:

how about President Reagan's
frequency, 13.440MHz I.s.b.,
used by Air Force One in flight?
An introductory section surveys
radio-teleprinter codes, including Cyrillic, and lists commercial
Z -code abbreviations.
ELECTRONIC
RONIti
SPEECH
Electronic Speech Recognition,

ed. George Bristow (of STC Net-
work Systems). Collins, 395

pages, hard covers, 30. Techniques, technology and applications described by 20 authors
from industry and the academic
world.
Data
Communications
and
LAN Technology
W. Sams & Co.), 256 pages, soft
covers, 10.95. Survey of broadcast receiving techniques for

v.h.f. and u.h.f. Unfortunately
much of the information relates
to products available only in the
US and to American installation
practice. However, some of the
more exotic antenna designs
have yet to cross the Atlantic,
and these could be of interest to
aerial experts over here.
various interfaces and protocols

work, and some practical case
studies. Clear explanations and
helpful diagrams.
Working with Microprocessors,
by Ian Sinclair. Collins, 142
pages, hard covers, 25. Hardware aspects of microprocessors
and other programmable chips,
aimed especially at designers
more accustomed to analogue
circuits. A case study deals with
the Chameleon controller developed by the Electronics Centre of Essex University.
Modern Electronic
Test
Equipment
TV i1tTIY'rrrrerS
and SGrr
t.iS'iRE3UTi[?n
SvS rertCts
Introduction to Knowledge Base

Systems, by R.A. Frost (University of Glasgow). Collins, 698
pages, soft covers, 18. Textbook
of AI theory and practice for
computing science students at
graduate or final -year under-
graduate level.
Radio and Television Servicing,

1985-86 Models, ed. R.N. Wainwright. Macdonald, 795 pages,
hard covers, 25. Circuits and
abridged servicing information
for various UK models by British
and foreign manufacturers.

Radio section includes clock
radios, cassette recorders, car
audio and personal stereo sets.
Modern Electronic Test Equipment, by Keith Brindley. Heinemann Newnes, 134 pages, soft
covers, 6.95. What's on the
market, what it can do and how it
works: guide for students and
others to the main categories of
modern test gear, including

meters both analogue and digital, oscilloscopes, counters, signal generators, spectrum analysers and a.t.e. Illustrated with
many diagrams and product
shots.
105
Carston Electronics Limited

Park Road, Teddington
Middlesex TW11 OAF
Telephone: 01-943 4477
Telex: 938120 CARLEC G
3
CIRCLE 48 FOR FURTHER DE'I'AILS
NEW OR USED?
Large companies often choose to buy second -user test
equipment, which has been serviced and re -calibrated, in
preference to new instruments. Cost saving is not the only reason
PETER FRAIMAN AND DAVID PRICE
In 1985, the total world market for test

and measurement products was estimated at $5000 million, of which 55%
was accounted for by the US market. In
recent years, the US share of the test and
measurement market has been gradually
decreasing due to faster growth in both
Japan and Europe. It has been estimated that
the European proportion of the market now
represents about 750 million and the UK
alone accounts for 270 million. Excluding
sales to the British defence market and
indirect sales for export, the British market
for test and measurement products (defined
as equipment such as oscilloscopes, signal
sources, and digital voltmeters that is sold to
UK companies) is currently estimated at 40
million per annum.
Hence, assuming this figure of 40m per
annum to be, at worst, static over the last
seven years, there is at least 300 million
worth of test equipment being used by
British industry at the present time. It is a
moot point how much of this equipment is
gathering dust on the shelf, either because it
was purchased to fit the specification of a
particular project, or because the service
manager finds that he now needs more
sophisticated and accurate instruments.
Estimates show that 15% of this total pool
of 300 million worth of test and measurement equipment is updated annually. The
trend is nowadays for test equipment manufacturers to bring out new models more
often - mainly because of the increasing
speed of technological innovation. British
industry is now beginning to replace its
older test and measurement equipment
much earlier in its life cycle. When Electronic Brokers started business over 19 years
ago in the second-user market, it was not
unusual to find that companies were using
equipment which was in some cases 20 years
old and they were fully prepared to buy more
of the same. This trend is slowly changing:
nowadays manufacturers replace test and
measurement equipment when it is 7-10
years old and, for the future, a replacement
period of 3-7 years is expected.
SECOND -USER MARKET

The buying and selling of second -user equipment has been an established part of the test
and measurement market for some time.
Without doubt, the second -user market is
here to stay. Second -user suppliers acquire
A DEC VAX
computer undergoing refurbishment at Electronic Brokers' headquarters.
and re -sell mainly high -end professional specification laid down by the manufacturer.
products, many of which, because of the Reputable second-user suppliers will also
trend described above, are only a couple of offer a full 12 -month warranty, as effective as
if it had come from the original manufacturyears old.
and
An important feature of second -user super, and continuing after -sales support
pliers is that they deal in `blue-chip' pro- service even well outside the warranty
ducts, such as are manufactured by Tektro- period. Before a sale is made they will be able
nix, Marconi Instruments, Hewlett Packard to offer impartial advice on equipment types
and Philips. Interestingly enough, the cus- and, where practicable, will even advise on
tomers for second -user equipment are also applications.
to be found at the `blue-chip' end of the
industry.
ADVANTAGES OF BUYING
Another major feature of second-user
SECOND -USER PRODUCTS
suppliers - and one that distinguishes them
from the traditional second-hand stockist - Several advantages accrue from buying test
is that the former do considerably more than and measurement equipment from a
just buy and sell equipment. Once acquired, second -user supplier. Cost is an obvious
a piece of equipment undergoes a complete advantage. Buying second -user equipment
electrical and mechanical refurbishment from a reputable supplier gives the user
and is then fully re -calibrated to the original guaranteed às -new' equipment at a fraction
107
of the cost of the manufacturer's list price.

Let us examine the question of costs in
more detail, and, with particular reference
to oscilloscopes, which are one of the most
important measuring tools for any engineer.
They account for by far the largest proportion of any capital expenditure on test and
measuring instruments, not necessarily by
value, but in terms of number of units.
PRICE PERFORMANCE
1976
1986
Fig.1. Price comparison: 20MHz oscillo-
scopes
1500
109 MHz
oscilloscopes
1000
im
2235
The last 10 years has seen an unprecedented

change in the design and cost effectiveness
of the lower bandwith oscilloscopes.
As a typical example, in 1976, the Tektronix 545 had a second-hand value of 275. If
we look at the price of the equivalent model,
bought new, for example the Hameg HM203,
we find that the price is only 270.
This relationship is shown diagrammatically in Fig. 1. As can be seen, in 1976, there
was a tremendous saving to be made by
purchasing second -user. By contrast in
1986, a saving of only 50 on the new price
of 270 could be realistically expected, not a
real incentive to pursue the second-user
route.
1986
1976
Fig.2. Price comparison: 100MHz oscillo-
scopes
loose
16Hz signal
source
o00
HP 86408
0000
ecco
2000
1976
1986
Fig.3. Price comparison:
sources
1GHz signal
If we now turn to the higher bandwith

oscilloscopes (Fig. 2), it can be seen that the
classic example of early 100MHz oscilloscope technology, the Tektronix 465, had a
second -user price of around 60% of the retail
price and in 1986, the modern equivalent,
the Tektronix 2235 has a retail value of
1430 and a second-user value of approximately 65% of this value.
From this it can be seen that the higher
bandwidth models are of comparatively
similar prices and enjoy a similar saving if
bought on the second -user market.
The indicator here, then, is that the
higher the technology, the higher the price
and therefore th greater the savings can be.
Extrapolating this relationship upwards
to, for example, high -frequency signal
sources and spectrum analysers, we find that
it does indeed hold true.
If we take as a specific example, the
Hewlett Packard 8640B option 002 1GHz
signal source, the story is plainly clear as
shown in Fig. 3. In 1976, a cost saving of
The Tektronix 2235, an example of larger cost saving in higher -priced equipment
one-third could be realised in purchasing

second -user; while in today's market, savings of 50% are quite common.
The reason for this can be traced to the
fact that technology has not moved as fast as
in the oscilloscope market, but also because
the same instrument is still being produced
10 years later: obviously there are some
older models available at greater savings

than would otherwise be possible.
Consequently, it would seem a fair
assumption to make that in the lower,
cheaper end of the test equipment market,
because of the advent of newer, better but
cheaper models, it seems wisest to choose
the new machine; however, in the higher
technology part of the market, large savings
on capital investment can be realised in the
wise choice of good, high -quality second user instruments.
Cost is not the only consideration in
buying second-user test equipment. A purchaser may want an instrument that is no
longer in a manufacturer's current catalogue but nevertheless is still in perfectly
sound working order. Instrument manufacturers are always under a great deal of
pressure to adopt the latest technology in
new products
a trend which is on the
increase, as discussed above. Because of this
pressure, it is harder for the manufacturers
to service the demand for older products
even though, in many instances, there is a
very real need for them.
A further advantage from buying second user test and measurement equipment is
that the supplier will often be able to supply
equipment which, because of the required
delivery date, could not be supplied by the
manufacturer.
How, then, is the potential user to establish whether his requirements can be met by
buying from a second -user supplier? The
obvious answer is "Ask". Suppliers continually receive inquiries about availability,
often for particular models of instruments
fitted with specific options. General inquiries are also very common "How can I
measure this?". Reputable second -user suppliers should be able to cope with all types of
questions and are often in a very good
position to give an unbiased answer, because
the very nature of his business relies on a
good network of contacts among sellers and
buyers of used equipment. Ideally, the
second-user supplier will maintain a computerized database of possible sources of
equipment and individual users' requirements, thereby enabling a speedy response
to an inquiry.
The second-user market is today a well established sector of the electronics and
computing industries. As has been discussed, many advantages accrue from buying
test and measurement equipment from a
reputable second-user supplier. In essence,
it makes sound business sense to consider
the second-user options when specifying test
and measurement equipment. The writers
welcome comments from people in the
industry.
Peter Fraiman is Managing Director of Electronic Brokers Ltd and David Price specializes in the sale ofsecond -user equipment.
INSTALL YOUR
OWN SYSTEM
AND SAVE
ECURITY
Control Unit
Lighting Controller DP 3570
re
Audible entry & exit warning.
- 240r cdcus.
Also available in kit form

with fully built-in electronics
Poppy Road,
Princes Risborough,
BUCKS. HP17 9DB
Tel. (084 44) 6326
R273231
only 14,95+VAT
uni,
Enclosure & fixings
S ir
Control Unit CA 1250
ONLY
44.95,
VAT
Order by 'phone or mail

or call at our showroom
and see
Olt
Please add 15 VAT and 75p P&P to all UK orders

Export no VAT - postage at cost
only 9.50 + VAT
money in control systems.

providing the following features
Built-in electronic siren drives
2 loud speakers
Provides exit and entrance
delays together with fixed
alarm time
Battery back-up with trickle
charge facility
Operates with magnetic
switches, pressure pads.
ultrasonic or R units
Anti -tamper and panic facility
dhesive silk screened label

700mm
Size 200 - 180
ondibns
Complete
systems
from only
Stabilised output voltage

2 operating modes full
alarm anti tamper and panic
facility
Screw connections for ease of
installation
only 2.95 + VAT

Suitable metal enclosure for
housing the ultrasonic module
type US 5063 Supplied with trie
ng p
39.95
Separate relay contacts for

external loads
1,", ieop facility
ors and
,cre s,arr
+ VAT
For
full information of system, and
accessories, send or call for details
OFF AIR FREQUENCY STANDARD

SUPPLY
7MH:
levels of discriminate
against false alarms
Crystal control for greater
stability
Adjustable range up to 1511
Built in delays
12V operation
This advanced module Lives
digital signal processing to
provide the highest level of
msinvily whilst disc nmmatinq
,chins) pot .'lia''.ilse
3
This tried and Inslerl control us.,

represents the finest value for
This attractive case rs designed to

house the control unit CA 1250.
together with the appropriate LED
indicators and key switch.
Supplied with the necessary
mounting pillars and punched
front panel, the unit is given a
professional appearance by an
35mm
only 13.95 + VAT

Price 19.95 + VAT
UNITS ON DEMONSTRATION
50
Detector US 5063
Individual Enclosure SC 5063
Monday to Friday 9.00- 5.00 p.m.

9.00- 1.00 p.m.
Saturday
Quartzlock
90
Digital Ultrasonic
for CA 1250
This brand new control panel provides

effective and reliable control of all types of
security installations. Using advanced
electronics, the unit automatically checks the loop circuits every time that it is
switched on, thereby reducing the possibility of false alarms and incorrect
operation. Using a simple on/off key switch, it is easily operated by all members
of the family. Additionally, 24hr personal attack and anti -tamper protection is
provided irrespective of whether or not the unit is switched on. housed in a
strong, attractive steel case, the unit is supplied with full operating instructions
and 2 keys. Supplied fully built and tested ready for installation.
51
Consisting of separare
transmitter ar,d receiver both of
which are housed in attractive
moulded cases. the system
provides an invisible modulated
beam over distances of op to 50ft
operating a relay when the bears.
is broken Intended for use in
security systems, but also ideal
for photographic and
measurement applications
ti
Wh,lsl n lender) ter sec unly

lighting applications, this
suitable for lighting patios,
pathways and gardens etc
Supplied complete with 500W
lamp, priced
ly 614
VAT
Protective grill, f1 95 -VAT
9
Easily installed, full instructions supplied.
Dept. WW 61
only 25.61 + VAT
This versatile module provides

timed switching of loads up to 3A
for preset times between 10 secs
and 5 mins, the timed period
being triggered by the opening or
closing of an external loop or
switch The built in 12V 250mA
HW 1250
Built-in electronic siren.
39.95 + VAT
iliSCOMP LIMITED
IF
13.95
+ VAT
power supply is available for

operating external sensors
Priced only 613.95 VAT Suitable
plastic enclosure, f2 85 VAT
Alarm Sounded memory.
separate loop inputs
FL 500
only
with automatic circuit testing and simple

on/off operation.
siren -set.
Infra -red System IR 1470
500W Quartz Halogen
Floodlight
CA 1382
Fully automatic
MODULES
ACCESSORIES
KITS
10MHz
tJFF
METER
LOCK
Nx
th!
..
L,-i,;
ei
001"84
OFF AIR FREQUENCY STANDARD
Model 2A
Provides high accuracy 1MHz & 10MHz for frequency calibration

you use Counters
Timers D Frequency Meters
Signal Sources & Generators or Radiotelephone Test Systems
If
M :JJum term
accuracy
1:1010
Long term
ageing or temperature coefficient
2:1011
without additional drift
This new design on CAD PCB
accommodates present & 1988 standard signals
DARTINGTON FREQUENCY STANDARDS

MOOR ROAD, STAVERTON, DEVON TQ9 6PB ENGLAND
Telex 42928 A/B WETRAV G (Quartzlock)
FIRST CLASS/NEXT POST DATA SERVICE 080 426 524
CIRCLE 99 FOR FURTHER DE'T'AILS
(19
P.
PHONE
0474 60521
4 LINES
INTEGRATED CIRCUITS
AN124
AN2140
AN240P
AN612
AN7116
AN7140
AN7145
AN7150
BA521
CA1352E
CA3086
CA3123E
HAI 366W
HA1377
HA1156W
HAI 339A
HAI 398
HA1551
LA1230
LA4031P
LA4102
LA4140
LA4400
LA4420
LA4422
LA4430
LA4461
LC7120
LC7130
LC7131
LM324N
LM380N8
LM380N14
LM383T
LM3900N
M51513L
M51515L
M515211
MB3712
2.50
2.50
2.80
2.15
1.50
3.50
3.50
2.95
3.35
1.75
0.46
1.50
3.50
3.50
1.50
2.95
2.75
2.95
1.95
1.96
2.95
2.95
4.15
1.95
2.50
2.50
3.95
3.25
3.50
5.50
0.45
1.50
1.75
2.95
3.50
2.30
2.95
1.50
2.00
MC1307P
1.00
MC1310P
ISO
MC1327
1.70
MC1349P
1.20
MC1351P
1.50
MC1357
2.35
MC1358
1.58
MC1495
3.00
MC1496
1.25
MC145106P7
7.95
MC1723
0.50
MC3357
2.75
ML231B
1.75
MSM5807
6.75
PLL02A
5.75
SAA500A
3.50
SAA1025
7.25
SAS560S
1.75
1.75
SAS570S
2.85
SAS580
SL917B
7.50
1.80
SL1310
SL1327
1.10
SL13270
1.10
SN76003N
3.95
SN76023N
3.95
SN76033N
3.95
SN76110N
0.89
SN76115N
1.25
SN76131N
1.30
SN76226DN 2.95
1.05
SN76226N
SN76533N
1.65
SN76544
2.65
SN76570N
1.00
SN76650N
1.15
SN76660N 0.80
STK014
7.95
SEMICONDUCTORS
4A112
AC125
AC126
AC127
AC128
AC128K
AC141
AC142K
AC176
AC176K
AC187
AC187K
AC188
AC188K
ACV17
AD142
AD143
AD149
AD161
AD162
40161/2
AF106
AF114
AF115
AF 116
AF 117
AF121
AF124
AF125
AF126
AF127
AF139
AF150
AF178
AF239
AFZ12
ASY27
AU106
AU107
AU110
AU113
BC107A
BC1078
BC108
BC108A
BC1088
BC109
BC109B
BC109C
0.10
BC182
BC182LB
BC183
BC183L
BC184LB
BC204
BC207B
BC208B
BC212
BC212L
BC212LA
BC213
BC213L
BC214
BC214C
BC214L
BC237B
BC238
BC239
BC251A
BC252A
BC258
BC258A
BC2284
BC300
BC301
BC303
BC3078
BC327
BC328
BC337
BC338
BC347A
BC461
BC478
BC527
BC547
BC548
BC549A
BC550
BC557
BC557B
BC558
BCV33A
0.11
80115
0.12
0.10
0.12
0.12
BD124P
BD131
BD132
BD133
BD135
0.25
0.20
0.45
0.20
0.28
0.32
0.28
0.45
0.22
0.31
0.25
0.28
0.25
0.37
1.15
0.79
0.82
0.70
0.39
0.39
0.90
0.50
1.95
2.95
2.95
2.95
0.60
0.65
0.35
0.32
0.65
0.40
0.60
1.95
0.42
3.75
0.85
4.50
3.50
3.50
4.50
0.11
0.11
BCt14
0.11
BC116A
8C117
8C119
BC125
BC139
BC140
0.15
0.19
0.24
0.25
0.20
BC141
BC142
0.25
80143
0.24
0.12
0.12
0.09
0.09
0.09
0.12
0.09
0.09
0.09
0.09
0.15
0.15
BC147A
BC147B
BC148A
BC148B
80149
80157
BC 158
BC159
BC1174
13C174A
BC177
BC178
0.31
0.21
DIODES
A119
BA115
B145
B148
B154
B156
8A157
BAX13
BAX16
BB105B
BT151
136126
86127
BY133
BY164
81176
BY179
51182
BY184
BT199
96206
0.80
0.13
0.16
0.17
0.06
0.15
0.30
0.04
0.06
0.30
0.79
0,10
0.11
0.15
0.45
1.20
0.63
0.55
0.35
0.40
0.14
0.10
0.10
0.10
0.09
0.09
0.10
0.13
0.13
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.09
0.12
0.12
0.15
0.25
0.39
0.30
0.30
0.30
0.26
0.09
010
0.10
0.10
0.09
0.13
0.35
0.20
0.20
0.10
0.10
0.10
0.14
0.08
0.80
0.10
1.60
0.30
0.59
0.42
D42
BD204
BD222
BD223
BD225
0.40
0.30
0.30
0.32
0.30
0.32
0.30
1.10
0.29
0.65
1.50
0.55
0.72
0.45
0.70
0.70
0.83
0.65
0.78
0.70
0.46
0.59
0.48
BY208-800
0.33
B6210-800
BY223
BY298-400
BY299.800
BYX10
BYX36-1509
0.33
0.90
0.22
0.22
0.20
80136
50137
50138
BD139
130140
BD144
BD150C
BD159
80160
80166
BD179
BD181
80182
BD183
50201
BD202
80203
0.20
BYX38-600R
B6X55-600
BVX71-600
B2Y95C30
CS4B
CS10B
0647
0690
0691
0695
06202
I92109
IN23B
19230
IN23ER
IN23WE
0.60
0.30
1.10
0.35
4.50
8.45
0.09
0.05
0.06
0.06
0.10
5.00
5.00
5.00
5.00
5.00
TBA396
TBA440N
1544800
TBA510
TBA5100
TBA520
TBA5200
TBA530
TBA5300
D232
D233
0234
D236
D237
D238
D242
D246
D376
D410
D434
D437
D438
0520
13539
D597
D589
D701
0702
D707
DX32
F115
F119
F119
F127
F154
F158
F160
F167
F173
F177
F178
F179
F180
F181
F182
F183
F184
F185
F194
F195
F196
F197
F198
F199
F200
F271
F273
F330
F337
F338
F355
F362
F363
F371
F394
F422
F457
F458
F459
F467
F494
F495
F595
F597
FR39
FR81
FR88
FR90
TT44
TT923
TT2002
TBA5400
TBA5500
TBA560C
TBA460CQ
TBA570
TBA651R
TBA720A
TBA7500
TBA800
TBA810AS
TBA810P
TBA820M
7568200
TBAB90
TBA920
TBA950/2X
TBA990
TCA270
TCA270S0
TCA650
TCA800
TCA940
TDA440
TDA1001
TDA1002A
TDA1006A
TDA1035
TDA1037
TDA1074A
TDA1170
TDA1190
TDA12700
TDA1327
7062002
2.55
1.25
2.50
2.50
1.10
1.10
1.10
1.10
TDA2003
TDA2004
TDA2005
TDA2006
0.35
0.35
0.35
0.49
0.40
0.40
0.65
0.75
0.32
0.65
0.65
0.75
0.75
0.65
0.65
0.95
0.45
1.25
1.25
0.90
1.50
0.35
0.35
0.65
0.39
0.20
0.22
0.27
0.27
0.22
0.38
0.26
0.34
0.29
0.29
0.29
0.29
0.28
0.28
5E991
BFT42
BFT43
BFW92
BFX29
BFX84
BFX85
BFX86
BFX88
BFY50
BFY51
BFV52
BFY90
BLY48
BRV39
0.16
0.14
0.40
0.15
0.30
0.28
0.28
0.28
0.26
0.18
0.34
0.29
0.32
0.37
0.38
0.65
0.25
0.19
0.32
0.32
0.36
0.36
0.68
0.45
0.45
0.23
0.25
0.23
0.25
0.30
1.50
F245
F257
F258
F259
TBA540
0.75
0.11
0.11
0.11
0.11
F241
95403
N5406
N5407
N5408
TELEX
966371
TOS -PM
SELECTRON HOUSE, SPRINGHEAD ENTERPRISE PARK

SPRINGHEAD RD, GRAVESEND, KENT DA11 8HD
STK015
7.95
11.95
STK025
15.50
STK043
11.95
STK078
STK433
5.95
STK435
7.95
STK437
7.95
STK439
7.95
11.50
STK461
TA7061AP
3.95
1671081,
1.50'
TA7120P
1.65
TA7130P
1.50
TA7176AP
2.95
TA7203
2.95
TA7204P
2.15
TA7205AP
1.15
TA7222AP
1.80
TA7227P
4.25
TA7310P
1.80
TA7313AP
2.95
TA7321P
2.25
TA7146P
2.50
TA7609P
3.95
TA7611AP
2.95
TAA310A
2.50
TAA320A
1.95
TAA350A
1.95
TAA570
1.95
TAA661B
1.95
TBA700
1.70
TBA120AS/B/C/
SNSB/T/U 1.00
TBA395
1.50
N4001
N4003
N4004
N4005
N4007
N4148
N4448
N5401
N5402
M. COMPONENTS LTD
0.04
0.04
1062020
TDA2030
TDA2190
TDA2522
1.25
1.35
1.95
1.45
1.45
1.00
2.50
2.45
2.65
0.89
1.65
1.65
0.75
1.45
2.50
1.65
2.35
1.49
1.50
1.50
3.50
6.95
1.65
3.50
2.95
2.95
2.50
2.50
1.95
1.95
1.95
2.15
5.50
1.70
1.95
1.95
2.95
2.95
1.95
2.95
2.80
3.95
1.95
TDA2523
TDA2524
TDA2530
TDA2532
TDA2540
TDA2545A
TDA2451
TDA2560
TDA2571A
TDA2581
1.75
0.35
0.35
0.85
0.30
0.26
0.32
0.30
0.25
RCA16335
SKE5F
0,80
1.45
TIP29
0.40
TIP29C
TIP30C
TIP31C
TIP32C
TIP33C
TIP348
TIP41A
TIP41C
TIP42C
TIP47
TIP120
TIP125
TIP142
TIP161
TIP2955
TIP3055
0.42
0.43
0.55
0.42
0.95
0.95
0.45
0.45
0.47
0.65
0.60
0.65
1.75
2.95
0.85
0.55
0.20
1.50
1.35
0.28
0.29
0.40
0.40
0.59
0.52
0.12
0.12
0.12
0.20
0.12
0.12
9.50
2.75
1.35
1.95
1.15
0.42
0.48
0.60
0.45
0.96
0.60
0.80
0.80
0.80
2.50
2.20
1.15
1.40
2.95
0.50
0.80
1.25
1.25
2.65
0.95
0.80
1.95
1.15
1.95
1.45
0.85
2.95
1.95
0.80
0.36
0.50
2.95
0.95
0.21
0.21.
0.25
0.77
139100
BR110
BR103
B9C4443
131100N0
131106
BT116
BT119
BT120
BU105
BU108
BU124
BUI 25
135126
BU204
BU205
BU208
BU208A
BU2080
BU3276
BU407
BU500
BU508A
BU526
BUB0Y
801698
MJ3000
MJE340
MJE520
MPSA13
MPSA92
MRF237
MRF450A
MRF453
MRF454
MRF455
MRF475
MRF477
1.75
0.45
0.26
0.49
0.55
1.15
20.85
1.49
1.20
3.15
1.65
1.95
1.69
1.25
1.25
1.60
1.55
1.30
1.39
1.52
1.85
1.20
1.24
2.25
1.95
1.90
2.25
1.70
1.98
0.40
0.48
0.29
0.30
4.95
13.95
17.50
26.50
17.50
2.95
10.00
19.95
MRF838
OC16W
2.50
0C23
1.50
1.50
2.25
2.25
0.75
0.75
0.55
0.45
0.55
0.85
0.95
0.50
3.50
1.45
1.45
0.58
0.66
2.48
0.90
0028
0C29
OC32
0C42
0C44
0C45
OC70
0071
0072
0075
0081
OC171
R20085
R2010B
R2322
R2323
R2540
HCA16334
2.95
1.95
1.95
1.95
1.95
2.15
2.15
2.15
4.50
2.95
1042593
2.95
TDA2600
6.50
TDA2610
3.50
TDA2611A 1.95
1062640
3.50
TDA2680A 2.75
TDA2690
2.45
TDA3310
2.95
TDA3560
5.50
UPC566H
2.95
UPC575C2 2.75
UPC1025H 1.95
UPC1028H 1.95
UPC1032H 1.50
UPC1156H 2.75
UPC1158H 0.75
UPC1157C2 1.95
UPC1181H 1.25
UPC1182H 2.95
UPC1185H 3.95
UPC1191V 1.50
UPC1350C 2.95
UPC1353C 2.45
UPC1365C 3.95
UPC2002H 1.95
555
0.36
556
0.60
723
0.50
741
0.35
747
0.50
748
0.35
7805
0.65
7808
0.60
7815
0.65
11091
N106/2
2N1308
2N2219
2N2222
2N2905
2N3053
2N3054
2N3055
2N3702
2N3703
2N3704
2N3705
2N3706
2N3708
2N3733
2N3733
2N3792
2N4427
2N4444
2N5294
2N5296
2N5298
2N5485
2N5496
2SA715
2SC495
2$C496
2SC1096
2SC1106
2SC1172V
2SC1173
25C 1306
2SC1307
2SC1364
2SC1449
2SC1678
2SC 1909
2SC1945
2SC1954
2SC1957
2SC1969
2SC2028
2SC2029
2SC2078
2SC2091
2SC2098
2SC2166
2SC2314
2SC2371
2SD234
3N211
3SK88
LINE OUTPUT TRANSFORMERS
0 05
0.05
0.06
0.02
0.10
0.12
0.14
0.12
0.13
0.16
0.16
0.04
0.15
0.20
ZENER
DIODES
DECCA 100
DECCA 1700 MONO
DECCA 1730
DECCA 2230
GEC 2040
GRUNDIG 1500
GRINDIG 510-6010.2222.5011-6011
ITT CVC20
ITT CVC30
PHILIPS GB
PHILIPS G9
PHILIPS G11
PIE 725
RBM 120A
TANDBERGE90
TELEFUNKEN711A
BZX61 Series
0.15
82688 Series
0.10
THORN
THORN
THORN
THORN
1590
8000
9000
9800
7.95
9.95
8.95
8.25
8.95
15.45
13.45
8.20
8.25
8.50
8.99
13.99
10.95
12.40
11.15
11.15
9.50
23.50
9.95
22.40
CATHODE RAY TUBES Please add 3 additional carriage per tube.

45.00
45.00
55.00
45,00
DG7.32
CME822GH
CME1428GH
19.00
25.00
45.00
CME1428W
CME1523W
CME1431GH
39.00
39.00
39.00
CME1431 W
39.00
DN13.78
CME202GH
CME2024W
CME2325W
CME3218W
CME3132GH
CME3155W
CRE1400
CV429
CV1450
CV1526
CV2185
CV2191
CV2193
CV5119
CV5320
CVX389
D9.110GH
45.00
45.00
45.00
45.00
45.00
45.00
25.00
89.00
35.00
19.00
15.00
19.00
15.00
85.00
85.00
55.00
39.50
45.00
65.00
35.00
35.00
55.00
49.50
85.00
85.00
55.00
59.00
59.00
59.00
59.00
59.00
75.00
75.00
59.00
55.00
55.00
55.00
53.00
55.00
65.00
F16-101GM
F16-101LD
F21-130GR
F21 -1301C
F31-10GM
F31-10GR
F31-10LC
F31-10LD
F31-12LD
F31.13GR
F31-13LD
F31.13LG
F41-123LC
F41-141LG
F41-142LC
M7-120W
M7-1200H
M14-100GM
M14.100LC
M17-151GVR
M17.151GR
M19.100W
M19-103W
M23-110GH
M23-11110
M23-112GM
M23-112GV
M23-112GW
M23-112KA
M24-120GM
M24-120LC
M24-120WAR
M24-121GH
M28-12GH
M28.13LC
M28-13LG
M28-13GR
M28-131GR
M28-133GH
M31-101GH
55.00
53.00
59.00
59.00
89.00
85.00
75.00
75.00
75.00
110.00
85.00
45.00
45.00
65.00
69.00
65.00
69.00
65.00
69.00
65.00
55.00
35.00
55.00
M31-182GR
M31-182GV
M31 -184W
M31-184GH
M31 -184P31
M31 -185W
M31-190GH
k431 -190014
CME822W
D10-21004
010-210GH68B
D10.230GH
010-230GM
D10293-06/90
013-30GH
013-51GL/26
013-51GM/26
D13J5GW01
D13-6000M
013-610GH
D13-511GH
D13-611GM
D13-830GH
D14.150GH
014-1500M
014-162GH/84
D14.172GR
014-172GV
D14-173GH
DI4.173GM
D14-173GR
D14-181GH98
D14-1810J
D14-181GM
D14 -1810M50
D14-182GH
D14-2008E
D14-20004/50
014-2000M
014-210GH
D14-270GW50
D14.310W
D14 -3200W82
D14-340GH/KM
014-340KA
D16-100GH
016-10004.65
016-1000W67
D16-1000H779
016-1000H97
018-180GH
021 -10tH
DG7.5
DB7.6
DB7.36
DG132
DH3-91
DH7.91
35.00
DP7.5
DP7.6
35.00
35.00
75.00
75.00
75.00
75.00
75.00
75.00
75.00
75.00
75.00
75.00
75.00
75.00
185.00
185.00
185.00
19.00
19.00
45.00
45.00
175.00
175.00
45.00
55.00
55.00
55.00
55.00
55.00
55.00
55.00
59.00
59.00
59.00
55.00
55.00
49.00
49.00
49.00
55.00
55.00
55.00
55.00
53.00
65.00
85.00
65.00
69.00
55.00
55.00
55.00
55.00
59.00
65.00
65.00
65.00
65.00
75.00
75.00
65.00
65.00
65.00
65.00
65.00
65.00
M31.190LA
M31.191GV
M31.220W
M31-270GV
M31 -271P31
M31-271GW
M31 -271W
1436-141W
M36-170LG
M38-101GH
M38-103GR
M38 -120W
M38-120WA
M38-121GHR
M38-121LA
M38-122GW
M38-140LA
M38-142LA
M38 -341P31
M38 -344P39
M40 -120W
M43 -12L0/01
M44-120LC
M44.120GR
M50-120GH
M50-120GR
M50-120GV
M50-120LC
M61 -120W
SE3NP31
SE4/D/P7
SE42BP31AL
SE42BP31
SE5FP31
1948H
V5004LD
V6048CAL
660483
V6064BP31
V6069GH
V6070P31
V7030
V7031GH
V7031/67A
V7035A
V7037GH
V8004GR
V8006GH
V8010A
VCR1396
3BPI
3DPI
3H/OBM
3WPI
4EPI
5BPI
5BHP1
65.00
65.00
65.00
65.00
65.00
59.00
65.00
65.00
65.00
65.00
65.00
65.00
65.00
75.00
40.00
45.00
55.00
55.00
55.00
65.00
59.00
59.00
49.00
55.00
55.00
65.00
59.00
59.00
59.00
49.00
45.00
65.00
65.00
65.00
11.50
11.50
11.50
55.00
18.50
30.00
9.00
30.00
30.00
30.00
10.00
15.00
39.00
13.50
17.50
25.00
69.00
15.00
39.00
45.00
80.00
75.90
75.00
75.00
78.50
58HPiFF
58HP31
5CPI
5T01A
6E P7/S
13BPI
138PA4
17DWP4
32J/1085
880/898/890/89L
1273
1564
1844
9442E1
954470M
95449GM
7709631
WIREWOUND
RESISTORS
4
7
11
watt
watt
wan
020
020
025
030
2134-10K
17 watt
1847-22K
1R -15K
118-15K
VIDEO SPARES E HEADS

VIDEO BE LT KITS
VIDEO HEADS
3HSS Suitable for Most JVC and
Ferguson models
.....29.50
3HSS(H) Suitable for Wads
VT5000. VT8000. VT6000. VT8500,
V T7000 ..................
33.95
4HSS Suitable for most National
Panasonic Models
....32.95
4HSS(UIN) Suitable for Panasonic
Models 370 and 380
......33.95
BETAMIX VIDEO HEADS

PS3B (1 Pin) Suitable for Sony and
Toshiba 5000 Series and NEC
P V 2400 ......
... 39.50
RSV -3-13 Suitable Ior Sony SL8000.
SL8080, SLD7ME
.....39.50
DSR-10-R Suitable for Sony SLC5.
SLC6. SLC7 .............................39.50
Sanyo Head for
VT09300/9500 .........................41.50
Sanyo Head for VTC
5300/5000.
.41.50
Akai VS9300/9500/
9800.....
.....
3.75
Ferguson 3616_
4.50
JVCH HR 3330/3600 4.50
JVC HR 3360/3660.....4.50
Panasonic NV 300 .....4.00
Panasonic NV 2900B 3.75
Panasonic 30008.
3.75
Panasonic NV7000.... 3.50
Panasonic NV8600B/
661064/08
.3.75
SANYO ORIGINAL VIDEO PARTS

SANYO ORIGINAL
PART NUMBER
4-529.108008
4-5271-23501
4-527V-51000
143-0.4904-00900
143-2-457T-05900
143-0-5451-01701
143-0-5457-01700
143-0-551T-VTC9300
143-0-6611-03800
143-0-6621-01201
143-0-9974-00100
MODEL
VTC5150
VARIOUS
5150
FVHP615
VTC9455
VARIOUS
VARIOUS
DESCRIPTION
Reel Motor 3.6W
Motor Assy.
Capston Motor
Gear Idler Assy.
Stopper Reel Base
VARIOUS
Loading Roller
VTC51 50
FVHP615
Reel Drive Pulley

Mod Kit IC 5663046
Video Head Cleaning Tape (VHS Automatic wet/dry)

Video Head Aerosol Cleaner
Video Copying Lead and Connector Kit 'ZN
E HT
MULTIPLIERS
ITT CVC20
ITT CVC30
PHILIPS 08.550
RANK T20A
THORN 3000/3500
THORN 8500
THORN 9000
UNIVERSAL TRIPLER
VARICAP TUNERS
U321
8.65
8.65
6.25
6.91
U322
U324
11.00
7.57
Pinch Roller Assy

Pinch Roller Assy.
Idler Assy.
1.95
0.95
0.95
8.50
1.95
VIDEO ALIGNMENT TAPES

S -2P Colour Bars 30 mm
S -3P Stairsteps 30 min.
49.50
49.50
DECCA. ITT, CVC206WAY

ITT VCV5-7-WAY
PHILIPS G8 (55016 -WAY
7.95
10.19
14.49
8 25
800
8.00
5.45
9.95
9.75
29.95
5.95
0.55
8.95
PUSH BUTTON UNITS
ELC1043/05 MOLLARD
ELC1043/06 MULLARD
REPLACEMENT
110
6.50
0.85
7.95
6.35
6.35
6.96
ELECTROLYTIC CAPACITORS
DECCA 30(400-400/350V)
DECCA80/100 (400/3056)
DECCA 1700
(200-200-400-350V)
GEC 2110 (600/300V)
ITT CVC20 (200/400V)
PHILIPS G (600/3006)
PHILIPS G9 (22004(63V)
PHILIPS 011 (470/250V)
73
Sanyo VTC 5500
Sanyo VTC 9300...
3 75
Sanyo VTC 9300P.. 3.90
Sharp VC 6300......... 3.75
Sharp VC 7300..........3.75
Sharp VC 8300..........3.75
Sharp VC 9300...........3.75
Sony SL 30006......... 3.75
Sony SL 8000/8080...4.50
Sony SL C7/J7............ 4.00
Toshiba V5470.......... 4.50
VA1040
VA1056S
VA1104
VA8650
VA1097
200MA QUICK BLOW FUSES

100MA
THERMISTORS
each
5p each
Op
200MA-5 AMP
0.23
0.23
0 70
0.45
0.25
20MM ANTI SURGE FUSES

100MA-800MA
IA-SAMP
15peach
12peach
2 85
2.99
SPARE & AIDS
355
2.25
1.80
2.25
1.19
2.35
HEAT SINK COMPOUND

FREEZE IT
SOLDA MOP
SWITCH CLEANER
WD40
1.90
0.95
0.64
0.85
1.75
PUSH PULL MAINS SWITCH

(DECCA. GFC, RANK, THORN
ETC.)
PYE IF GAIN MODULE
ANODE CAP (27kV)
1.02
6.99
0.69
P.
PHONE
0474 60521
4 LINES
FROM OUR
STOCK OF BRANDED VALVES
A SELECTION
3231
24.50
7.50
11.50
11.50
14.95
6.50
35.00
37.50
27.50
11.50
24.00
24.00
4.00
4.00
59.75
39.00
39.00
6.00
14.00
0.70
1.25
2.00
4.50
2.50
3L63
2.00
1714
1834
1998
2087
2134
2293
2426
2599
2792
2900
3042
2283
1C/WDD
/C/THI
.CT22
H221
1H238
1_60
1N1
1RP12
1RP34
1RP35
3211
38814
3IK
33E
'.3JA
55.00
19.00
22.0
20.00
20.00
65.00
32.00
;6A
:1108
1134
2.11484
1149/1
1150/1
115.0
195.00
135.00
:1534
.3E
32.00
29.50
'.C3L
0.90
301006
3.50
CV Nos prices
on request
33A
27.50
1.20
363
22.50
3441
3442
17.50
3490
4.50
125.00
34100
JAF91
0.70
DAF96
0.65
1.75
DC70
1.20
DC90
DCX-4-500
25.0
DE716
DE718
DET22
DET23
0E724
0E725
DET29
28.50
28.50
35.00
35.00
39.00
22.00
32.00
EBC91
0.90
EBF80
EBF83
EBF85
EBF89
EBF93
0.95
0.95
0.95
0.70
0.95
EBL1
2.50
EBL21
2.00
EC52
0.75
EC70
1.75
EC81
7.95
EC86
1.00
EC88
1.00
1.10
EC90
EC91
5.50
EC92
1.95
EC93
1.50
EC95
7.00
EC97
1.10
12.00
EC8010
ECC32
3.50
ECC33
3.50
ECC35
3.50
ECC81
1.15
ECC81 Special
2.25
Ouality
ECC82 Philip's
1.95
ECC83
0.65
ECC83 Bomar
1.35
ECC83 Philips
1.95
ECC83 Siemans
2.50
ECC83 Tungsram
1.50
ECC84
0.50
ECC85
0.75
ECC86
2.75
ECC88
0.95
ECC91
2.0
ECC180
0.72
ECC189
1.95
ECC01S
3.50
4.95
ECC803S
ECC804
0.0
ECC200 12.00
1.15
ECF80
ECF82
1.15
ECF86
1.70
ECF20
1.85
ECF202
1.85
ECF01
0.85
ECF805
2.50
ECF80
10.25
2.0
ECH3
ECHO
3.00
ECH35
3.50
ECH42
1.50
DF91
1.00
ECH81
1.00
0F92
DF96
DF97
DH63
DH77
DH79
DH149
0.60
0.65
1.00
1.20
0.90
0.56
2.00
0.90
ECH83
ECH84
ECH2000
1.00
1.00
1.50
0.60
0.79
2.50
0.74
0.69
0.95
0.69
2.50
DK91
DK92
DL35
DL63
13170
0173
DL92
0193
DL94
0196
DLS10
DLS16
DM70
DM10
1.20
2.50
1.00
2.50
1.50
0.95
1.10
2.50
2.50
13.50
10.00
1.95
3.50
1.50
0.65
0.72
29.50
DY51
DY86/87
DY802
E801
12.0
E811
E82CC
3.50
E83CC
3.50
E839
5.50
E86C
9.50
E88C
7.95
E88CC
3.50
E88CC Siemans
Special
5.95
E9OCC
E9OF
E91 H
E92CC
E999
E1301
E182CC
E180F
E186F
E188CC
E17
E2809
E283CC
E288CC
0810F
E1148
E1524
EA50
EA76
E479
EABC80
EAC91
EAF42
EAF801
EB34
E841
E891
E8C33
EBC41
EBC81
EBC90
7.95
7.95
4.50
3.95
6.99
18.50
9.00
6.50
8.50
7.50
15.00
19.50
10.00
13.50
29.50
1.00
6.95
1.00
1.95
1.95
0.70
2.50
1.20
2.00
1.50
3.95
0.85
2.50
1.95
1.50
0.0
ECLO
ECL82
ECL83
ECL84
ECL85
ECL66
ECL05
EF37A
EF39
EF40
EF41
EF42
EF5O
EF55
EF70
EF71
EF72
EF73
EF0
EF83
EF85
EF86
EF86 Mullard
1.50
4.50
3.50
3.50
2.50
4.95
1.20
1.50
1.20
1.00
0.55
3.95
0.50
2.25
4.50
EF89
1.50
EF91
1.95
EF92
2.15
EF93
0.95
EF94
0.95
EF95
1.95
EF97
0.90
EF98
0.90
EF183
0.65
EF184
0.65
EF730
1.80
EF731
3.50
EF732
3.50
EF80
11.00
19.50
EF04S
EF805S
13.50
14.50
EF806S
EF812
0.65
EFL200
1.50
EI -190
0.72
F090
0.95
EL32
0.95
EL33
5.00
EL34
2.25
E134 Mutlard/
Philips
4.50
EL36
1.95
EL37
9.00
EL38
6.50
EL41
3.50
EL42
2.00
EL81
6.95
EL83
5.95
EL84 Brimar 0.95
EL84 Mullard 2.95
EL85
4.50
EL86
1.25
EL90
1.75
EL91
6.00
1.75
EL95
EL153
12.15
E1183E
EL18P
EL360
EL500
EL504
EL509
EL519
EL802
EL821
EL822
EMI
EM4
EM80
3.50
3.50
6.75
1.40
1.40
5.25
6.95
3.65
8.50
12.95
9.00
9.00
0.70
0.70
1.65
3.95
2.50
15.00
1.95
4.50
0.80
2.35
1.50
5.95
0.50
0.55
5.50
0.70
0.75
2.75
2.75
0.75
0.75
1.50
2.95
2.95
9.00
6.95
9.00
17.50
17.50
17.50
EM81
EM84
EM85
EM87
EN32
EN91
EN92
EY51
EY81
EY83
EY84
E786/87
EY88
EY91
EY802
EX35
9240
EZ41
EZ80
EZ81
EZ90
F606
FWA/80
G55/1K
0180/2M
G240/2D
GC10B
GC10D
GC10/48
GC10/4E
GC12/4B
GD86W
GDT120M
GN4
GN10
GR1OG
GS10C
GS10H
GS12D
GT1C
GT1CS/S
G7N175M
GTR150W
GU20
GU0
GXU1
GXU3
GXUOSS
GY501
GY802
0230
GZ31
GZ32
GZ33
GZ34
GZ37
314491
HA8C0
HBC90
HBC91
9993
HF94
HK90
HL2K
HL23DD
HL41
HL42DD
HL90
HL92
M. COMPONENTS LTD
TELEX
966371
TOS -PM
SELECTRON HOUSE, SPRINGHEAD ENTERPRISE PARK

SPRINGHEAD RD, GRAVESEND, KENT DA11 8HD
17.0
17.50
6.00
5.00
6.00
15.00
4.00
16.50
12.00
12.00
14.00
13.00
8.00
1.00
35.00
17.50
13.50
24.00
14.50
1.50
1.50
1.50
1.50
1.50
4.50
2.15
4.50
1.00
0.90
0.75
0.80
0.75
1.50
1.05
4.95
4.00
3.0
3.50
0.70
1.50
HL133xDD 3.50
HT2
4.00
HY0
1.00
HVR2
3.00
JP9-7A
60.00
K3118
85.00
KR6/3
45.0
KTBC
7.0
KT33C
3.50
KT36
2.00
KT44
4.00
KT45
4.00
K161
5.00
KT63
2.00
KT66 USA 9.95
K766 GEC 17.50
KT66 Sp. Yellow
Spot
19.50
K767
9.00
KT77 Gold Lion
10.95
KT81
7.00
K788 USA 10.95
K788 G Lion
18.95
KTW61
2.50
KTW62
2.50
KTW63
2.00
KT263
2.50
LI 02/2K
6.95
12.00
11022K
187-20
95.0
LS913
6.95
M02A
60.00
M537A
60.00
M5143
155.00
M8079
6.00
M8082
7.50
M8083
3.25
M8091
7.50
M8096
3.00
M8098
5.50
M8099
5.00
M810
5.50
M8136
7.00
M8137
7.95
M8161
6.50
M8162
5.50
M8163
5.50
M8190
M8195
M8196
M8204
M8223
M8224
M8225
ME1401
ME1402
ME1501
MH4
MHL6
ML4
MS48
MU14
MZ1-100
N37
N78
042
OA2WA
043
OB2
OB2WA
0C2
0C3
OD3
0M4
OM5B
0M6
ORP43
ORP50
P61
P41
PABC80
PC86
PC88
PC92
PC97
PC60
PC900
PCC84
PCC85
PCC88
PCC89
PCC189
PCC805
PCC80
PCE82
PCF80
PCF82
PCF84
PCF86
PCF87
PCF200
PCF201
PCF800
PCF801
PCF802
4.50
6.50
5.50
5.50
4.50
2.00
3.95
29.50
29.50
14.00
3.50
4.00
4.50
5.50
3.50
125.00
12.50
9.85
0.85
2.50
2.50
0.85
2.50
2.50
1.50
1.70
1.00
3.00
1.75
2.50
3.95
2.50
2.50
0.75
0.75
0.75
3.50
1.10
1.10
1.25
0.40
0.55
0.70
0.70
0.70
0.70
0.80
0.80
0.65
0.60
0.65
1.20
0.40
1.80
1.80
0.40
1.35
PCF05
PCF80
PCF808
PCH200
PCL82
PCL83
PCL84
PCL85
PCL86
PCL80
PCL05
PE1-100
PEN25
PEN40DD
PEN45
PEN45DD
PNE46
0.0
1.25
1.00
1.25
1.50
0.85
2.50
0.75
0.80
0.85
0.80
0.90
69.00
2.00
2.50
3.00
3.00
2.00
9E0-085 42.0
PFL20
0.95
PL21
2.50
P136
PL38
0.95
1.50
0.72
0.72
0.60
0.52
0.78
1.00
1.75
1.00
12.50
1.10
1.15
1.75
4.85
4.95
3.50
2.95
29.50
PL81
PL81A
PL82
PL83
PL84
9188
PL95
PL302
PL345
PL50
P1504
PL50
PL509
PL519
PL802T
PL820
PL5557
P732
PY33
0.0
QS1203
051205
001206
001207
001208
001209
QS1210
001211
OS1212
001213
QS1215
001218
0U37
OV03-12
0005-25
OV06-20
OV08-100 145.00
OV2-2500 45.00
073-125
65.00
0Y4-250
70.00
074-400
76.00
R10
4.00
R16
12.0
R17
R18
R19
R20
1.50
2.50
2.50
1.20
R1169
RG1-125
55.00
4.95
901-2404 14.50
RG3.250A
3.50
RG3-1250A 35.00
R021125
62.50
RK -208
12.00
RL16
1.50
RPL16
12.0
RP713
2.50
RPY43
2.50
RPY82
2.50
RR3-250
15.00
RR3-1250 35.00
RS613
45.00
RS685
54.95
RSS688
52.15
06917
5.95
06933
28.95
011E12
38.00
00V0 -40A
15.00
25.00
27.50
00V0 -40A
Mullard
45.00
00V07-50 63.50
0020-20 42.50
0075/20
1.50
0075/40
0092/10
QS95/10
00108/45
00150/15
0S150/30
OS150/45
001200
OS1202
3.0
5.00
4.85
4.00
6.95
1.15
7.00
3.95
3.95
7502
Y65
YD110
7J1060
711020
115.0
25.0
6.95
75.00
265.00
Z70U
3.00
0.60
19.85
18.95
12.50
1.50
Z749
2759
Z803U
ZA1000
9.0
15.0
4.00
8.0
8.0
ZM1020
ZM1021
ZM1023
ZM1041
ZM1082
ZM1084
ZM1177
ZM1202
ZM1263
ZM1612
6.00
8.00
7.95
SC1/1100
SC1/120
SC1/1300
SC1/20
SP41
SP42
SP48
SS501
3.0
9.00
10.00
9.00
55.00
4.00
3.00
4.95
35.00
1.50
STV280/40 11.95
STV280/80 19.95
SU42
4.95
ST11
T82.5/30 85.0
TB2-300
45.00
783-200 395.00
TD1-104 25.00
TD0-10F 35.00
TD3-12
4.0
TDD4
5.50
TP25
1.50
TSP4
7.0
1711
1.0
T721
45.00
1722
45.0
57.0
1710
14.0
1A3
1C6
14E4
1B3GT
1622
1627
1835A
18634
1C1
1C5GT
1FD1
103GT
1J3GT
103
1N2
1N5GT
1928
1P39
4.50
1.20
3.50
1.95
10.0
55.00
45.00
75.00
2.0
2.0
2.0
2.50
2.50
2.50
4.50
2.50
25.00
19.50
TTR-31MR 65.00
TY2-125A 85.0
1115
0.0
174
1.00
774.40
104
1.75
1.00
1.40
8.95
85.0
178-600W
1U5
365.00
1102/250 375.00
U18.20
2.75
1X28
122
U19
U24
U25
U26
U37
11.95
2.00
0.90
0.90
9.00
6.95
2.00
U41
UO
3.0
U82
U191
U192
U193
0.70
1.0
U251
11801
0.65
1.00
0.75
0.65
UAF42
UBF80
UBC41
UBC81
UBF89
UBL21
UC92
UCC84
UCC85
UCF80
UCH21
UCH41
UCH42
UCH81
UCL82
UCL83
1.0
0.0
UF41
UF42
1.15
1.15
1.75
1.20
UF0
UF85
UFB9
UL84
UL85
UU5
UU7
UU8
U741
2.25
1.0
1.00
1.75
1.20
0.70
0.60
1.00
1.20
2.50
2.50
1.0
1.75
2.50
2.0
3.0
1.0
0.85
3.50
8.0
9.00
3.50
U185
0.70
V2354/1 /1 250.00
02384/10 295.00
0246N2K 315.00
02406/1K 225.00
V241C/1K 195.00
V339
3.0
V453
12.0
015631
10.95
VP4B
VP133
4.50
2.00
24S154
287
2822
2C39A
2C3984
2C40
2C42
2C43
2C51
2C53
2CY5
2021
2021W
11.0
1.0
69.50
32.50
39.50
37.00
29.50
60.00
0.75
45.0
1.50
1.95
2.0
2E22
49.00
2E26
7.95
2J42
93.0
2J55
350.00
2025
35.0
2K25 Raytheon
2026
2K29
2048
2056
2X24
34/1076
34/108A
34/1096
34/1106
3/141K
34/1471
3/167M
3N2
3A3
344
345
3115
3472
362
384
367
3B24
3626
3628
3BZ6
3C4
3023
3C45
3CB6
3CN38A
3CS6
3CX3
3CY5
306
4E27
4GS7
4J52
4JC6A
4076
4X1504
54/1020
54152M
541630
5A1700
54-180M
5A -206K
5AM8
5AN8
54134
5404
1.00
19.00
24.0
1.50
2.50
0.95
2.50
1.50
4.50
63305
600613
60764
6DW4
6E5
6E44
6EA7
57301
52407
6/3012
6N203K
647
6A8G
6AC7
6AG5
6AG7
6AH6
64J4
64J7
1..0
696
6405
6406
6415
6AM4
1.95
2.50
6AM5
6AM6
6AN5
64584
6405
6408
6AR5
6408
6405
6406
6AS7G
6476
6478
64U4
6AU5GT
6AU6
6AV6
6AWBA
6AX4GT
64736
6BE6
66060
6804
68K7A
6816
6818
68M6
68M8
68N4
68N6
6857
68N8
6805
6807A
6817074
68R5
6607
6608
68984
6BS7
6BW4
68W6
6BW7
68W8
68X6
68X7GT
6G6G
6GE5
60H84
60K5
6006
6GM6
9007
6GV7
6GW6
6GW8
6.0
1.95
4.50
3.50
1.75
0.85
5.95
3.95
61864
6JE6C
6.108
6JS6C
0.470
6K7G
608G
6KD6
6KM8
6KT8
1.0
2.50
4.50
0.75
1.75
2.0
601707
6SN7GT
6007
6007
60407
6U6WA
6U8
6U84
6960
60607
6VGG
676G
6X2N
fix
6.501
6x5017
6x88
7A6
7A7
7AD7
74U7
786
787
7C5
706
7E7
7H7
717
714
888
8810
8805
8F07
1002
100E7
10EW7
1091
10006
10914
10918
101D12
11E2R
11E3
11R3
1246
'
124H7GT
12415
12476
12477
12AT7WA
124t16
12417
124V6
124V7
124X7G7
124X7
12AX7WA
12477
124274
1284A
121346
12BE6
1.15
7.50
1.50
1.95
0.95
6106
5.50
6N7
6N7GT
2.0
2.0
6915
6925
6926
1.50
6928
2.00
1.75
1.20
2.0
4.0
4.0
20P3
20P4
2095
21J26
211U8
2481
2513068
251607
25806
2901
30912
2.50
3.50
2.50
2.50
3.50
5.50
2.50
2.50
2.50
1.95
1.95
1.25
2.50
2.95
0.75
1.95
2.50
0.78
0.65
45.00
55.00
5.50
3.95
1.50
4.95
1.00
1.25
1.15
2.50
1.50
0.65
1.95
2.0
1.0
0.65
2.0
3.95
1.95
4.50
1.50
1.95
12E1
19.0
12E14
12GN7
12HG7
12HG7A
12J5GT
12J7GT
12JZ8
1205
12K7GT
1208
12SA7GT
12SG7
12SH7
12007
12017
38.00
3.95
4.0
30FL12
30FL13
309114
3011
30115
301_17
30P4MR
30912
30P18
30919
30PL1
309113
30P114
31JS6C
334115OM
35A5
351607
3523
38HE7
400D6
42
47
50A5
5005
50CD6G
50EH5
50JY6
52KU
53CG
61S97
7561
75C1
83
84
8541
8542
04V
90C1
90CG
90CV
91AG
92AG
92AV
9541
10E1
10801
15082
15002
15004
155UG
18587
211
274A
307
328A
3884
42545
431U
572B
705A
708A
715C
724A
726A
803
805
807
810
8114
1.0
1.35
0.95
1.10
1.25
0.45
0.0
0.0
1.00
1.0
0.0
1.00
2.50
0.60
1.75
5.50
19.50
4.50
2.00
1.85
4.50
5.0
6.95
6.00
1.50
0.95
1.15
1.50
2.95
2.00
15.00
4.50
3.50
2.50
958A
1299A
1619
1625
1626
2050W
2050
2051
3534
4044
927
1927
4212E
4313C
4328D
5636
5642
5651
5654
5663
5670
5672
5675
5678
5687
5692
5696
5704
5718
5725
5726
5727
5749
5750
5751
5763
5814A
5823
5829WA
5840
5842
5847
5879
5886
5894
5899
5963
5065
6005
6012
6021
6057
6058
6059
6060
6062
6063
6064
6067
6072
080
00004
4.0
6132
6136
8.50
61468
3.0
6.50
1.95
15.00
3.50
13.50
12.0
9.00
19.0
15.00
6.0
10.00
1.50
6.50
2.50
2.15
25.00
1.50
33.50
15.00
5.00
15.00
17.50
8.00
4.50
55.00
8.0
8.0
45.00
275.0
75.0
14.95
59.00
1.95
85.0
812A
813
15.00
35.00
23.50
8298
14.0
833A
866A
872A
873
884
930
931A
954
955
95.00
'6.0
20.0
60.00
5.50
9.95
13.95
1.00
1.00
6155
6156
6157
6158
6201
6205
6211
6267
6350
6360
6386
6463
6545
6550
6688
6870
6887
68838
6973
7025
7027A
7032
7059
7167
7189
7193
7199
7247
7360
7462
7475
7488
7527
7551
7558
7586
7587
77914
7609
7733
7788
7815
7868
8012
890
18042
18045
18046
1.00
0.60
2.50
3.00
3.00
6.95
5.50
5.50
4.00
10.95
15.00
25.00
250.00
4.00
9.00
5.50
9.50
2.50
1.95
1.95
3.25
4.50
28.00
7.50
4.50
3.50
3.50
3.50
6.15
2.50
2.50
2.50
2.50
1.85
2.95
5.75
3.25
9.50
6.50
3.50
11.00
10.95
5.00
13.95
39.50
4.50
1.75
2.25
1.85
16.0
3.65
3.75
3.95
3.75
2.25
4.50
2.00
3.25
7.00
4.20
8.50
9.50
10.50
2.50
9.50
65.00
65.00
2.50
3.20
6.45
6.95
2.50
4.50
3.50
4.50
14.0
7.50
8.50
10.95
6.50
11.50
9.50
9.95
5.95
2.50
4.50
2.00
2.50
3.95
3.50
7.50
7.50
2.95
13.50
15.0
5.0
125.00
85.0
6.95
9.45
15.00
29.50
4.95
47.0
5.50
29.50
49.50
3.95
05.00
7.50
10.50
10.00
11.50
CALLERS WELCOME
AUDIO TAPE HEADS
1.15
4.50
3.95
0.75
0.72
3.95
0.70
4.95
2.15
2.15
5.50
1.50
5.35
1.50
4.00
0.48
3.50
20P1
6.00
3.50
3.50
2.50
9.00
17.00
35.00
25.00
33.50
9.00
10.50
0.70
7.95
0.95
0.55
0.60
1.95
1.15
4.95
2.50
39.50
2.95
1.75
1.75
19.50
6.50
0.40
1.48
0.95
'
4.00
1.95
85.00
1.65
1.65
20A2
20D1
20196
2011
3F5
30911
4.50
3.95
3.50
2.95
1.95
1.50
1.95
1.95
4.75
1.95
1.95
1.50
1200707 1.95
12SN7GT
1.85
12007
2.50
12X4
1.95
1303
3.20
1307
3.20
1309
3.20
13DE7
2.50
13DR7
2.95
13E1
145.00
13EM7
3.50
1407
1.95
16075
2.95
178E3
2.0
170W4A
2.95
17E W8
0.95
17JZ8
4.50
61D20
6LF6
61J8
906
3.50
1.75
2.75
2.50
1.95
1.20
3.50
3.50
120068
9H4
9H4R
9H5
29006
30017
30018
12816
12045
120X6
9405
940407
906
903
1.75
1.50
2.0
12C8
80135
2.0
126H74
126774
803
2.25
4.50
4.15
4.50
5.50
2.0
4.0
2.0
115.00
0.58
1.0
1.0
120W44
6L600(GE) 4.0
61601
1.95
607
607GT
12406
3.15
1.50
1.35
1.50
2.50
1.35
1.20
1.35
1.35
0.85
1.35
1.35
1.95
1.75
3.50
1.15
1.50
1.25
1.50
1.00
3.951.00
1.50
4.95
2.15
3.15
2.50
4.95
4.15
2.00
3.00
6.50
2.50
2.95
2.50
3.15
3.95
2.95
6115
6119
616GC
4.50
0.95
0.75
2.50
1.95
1.95
3.95
9.50
2.50
1.95
1.95
5.50
2.0
611
2.00
1.50
1.95
2.65
2.15
2.50
2.0
691
6H3N
6H6
6H6GT
6HF5
6HF8
6H86
6J4
6J4WA
6J5
6J6
6J7
3.25
6SK7GT
0.0
2.50
6G75
0.60
66J7G7
6807
5.50
1.50
3.00
1.00
2.75
2.50
0.60
1.25
1.25
1.25
1.25
17.00
1.95
2.95
5.50
3.95
6707
2.0
2.0
6SC7
6SG7
6SH7
2.0
6F6G
697
6F12
6913
6914
6917
6F21
6923
6F24
6F25
6F28
6F32
6F33
6FG5
2.00
1.50
1.95
2.50
6544
604701
1.75
2.50
2.50
1.95
1.75
2.95
2.95
4.50
2.00
4.95
2.50
6EV7
6EW6
6EW7
6F1
6F5
1.95
1.50
0.70
9.00
4.95
6137G
2.50
6E48
6E88
6EM5
6EM7
6EU7
6EU8
58.110M
58.254M
5B -255M
58.256M
15.0
56.257M
15.00
58-258M
14.50
5022
125.0
5CL8A
2.50
5.110E 2950.00
5R4G8
3.50
5R4GY
3.50
574
5.95
5U4G
2.95
5U4GB
4.50
5V4G
1.50
1.50
1.50
15.00
1.50
606
6DC6
60J8
6DK6
2.15
1.20
2.00
1.50
10.00
14.50
19.50
68318
66.16
10.0
24.0
6CW4
6.25
9.00
6BH6
4.95
4.50
6057
10.0
3.50
0.95
3.00
1.95
3.0
6CS6
10.00
4.0
11.00
12.00
11.50
7.50
10.00
3.95
3.95
1.10
4.50
0.95
3.35
6CM7
9.0
66484
9.00
6055
35.00
9.50
6BA7
5.0
6016
6C184
1.50
250.00
12.0
6CF6
6CG7
6CH6
6CL3
398.50
195.00
2.25
75.00
2.95
250.0
140.0
95.00
600604
95.0
79.0
6428
667
688G
6810
6846
75.0
6066
125.00
4XC150B
2.50
2.95
1.25
1.95
2.50
1.50
2.50
2.50
4.95
3.50
3.95
1.95
4.50
1.50
2.25
6.95
3.95
3.25
1.50
1.60
2.95
0.75
0.95
6.50
2.50
2.35
0.95
6.50
5.95
2.50
1.50
2.15
3.95
4.95
2.50
6018
6C44
6CA7
6CB5
4CX2506 49.0
4CX250B EIMAC
59.50
4032
125.00
40X250135 75.0
4CX250K EIMAC
95.00
40X1250 EIMAC
400350F
12.0
6C4
6C5
6C6
6CBG
6011
6827
1100.0
195.00
195.00
1.20
6B26
1.95
1.95
1.75
2.50
115.00
59.00
1.75
1.95
4C27
25.00
4C28
25.00
4C35
145.00
4CX1000A
425.00
4CX4000A
195.00
65.0
29.50
49.50
9.50
79.50
67.50
425.00
35.00
711070
711071
711290
Z77
2302C
2359
2505S
2520M
Z521M
ZM105
SC1/80
485518
4-654
4687A
4.250A
4.4004
4-10004
4832
433074
4626
YL100
ZA1001
SI 30P
3EJ7
3V4
3W4GT
4C X3504
15.0
5.59
5.95
5.00
6,00
5.00
6.00
9.00
5.00
3D214
3E22
3EH7
29.0
10.00
11144
0090-20
X91-6404
12.0
Mullard
00V0-10
3.00
2.00
1.50
1.15
Vi52
2.50
VU29
4.50
VU39
1.50
W21
4.50
W77
5.00
W729
1.00
W739
1.50
X24
4.50
X66/065
4.95
X76M
1.95
XC24
1.50
XC25
0.50
XFW47
1.50
XFW50
1.50
X01-2500 75.00
XG2-6400 135.00
XG5-500 22.50
XL628FT
7.50
XNP12
2.50
XR1-16004 49.50
X91-3204 79.50
VR101
V105/30
VR150/30
0104/1K
0109/1K
0130
UABCO
P782
P783
V975.30
A302K
0.50
0.70
0.70
0.70
9788
0.65
PY500A
1.95
97800
0.79
PY01
0.79
083-30 54.95
Q83-1750 139.50
0135-350 495.00
0E03-10
4.95
0E08-20 145.00
65.00
OF40
0925
1.00
00E02-5 19.50
00E03-12 7.95
00E03-20 35.00
00E0-40 45.00
00V02-6 19.50
00V0-10 5.50
PY81
4.15
3.95
1.05
0.90
0.90
3.15
1.50
1.50
3.20
5.00
2.10
5.00
9.50
5.75
1.75
29.50
MONO HEAD
1.50
3.50
2.95
AUTOREVERSE
STEREO HEAD
ELECTRO.OPTICAL
95247
9677M
P4231BAM
26.00
22.00
19.00
VALVE AND CRT BASES

650
5.50
87G
0.25
B7G SKID 0.25
1.0
88G
B8H
0.70
B9A
0.35
B94 SKT
0.40
B9G
0.75
8100
0.20
8138
0.50
814A
3.00
12PIN CRT 0.95
500101OR 2.95
OCTAL
0.35
SK610
35.00
1105
1.75
UX7
1.75
CANS
0.30
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112
WORKFILE
We include this round -up of jobs cu rently on offer in the electronics industry as the first in a regular series on careers. There appears to be a certain
amount of confusion about the requirements likely to be specified by employers for the kind of job one would like to do, so to try to help clear the way we
are asking personnel officers and directors to give their views on the proper approach to a career in electronics.
It is evident from the list below that a majority of positions are of the degree level, but there is still a large number for which HNC, HND or even 0-levels
are needed or for which experience alone is enough, particularly in sales. There are even some advertisers who do not mention their requirements at ail.
Area
Company
Contact
Personnel needed
Quals
Freephone Plessey
Roke Manor
0784 34322
Research
Degree
PBX/comp. interfacing
Degree
20-25k
Data communications
Wide range of activity
C.Eng.
Degree
11-15k
South-east
0703 31818
0322 241099
0272 795319
I. Hickman,
GEC Avionics Ltd,
Freepost, Elstree Way
Borehamwood, Herts.
0635 33445
Micro control (chief engineer)
Degree, HND
15k
Bristol
Cambridge
Herts. and Essex
Chessington
0223 311316
0223 355427
0202 292155
01-397 5281
Computer networking
Dig. systems(noise & vibr'n)
Degree
Degree
Degree
Degree
01623 1266
0223 214411
01-460 5575
C21455 6255
see "Hardware"
01-397 5281
Freephone Plessey
Roke Manor
0533 544 193
0223 311316
0223 355427
0202 292155
0272 671881
0749 72081 x 227
Systems analysts
Software engineers
Software engineers
Software manager
Software engineers
Software engineers (radar)
Wide range of research
A lev./deg.
Negotiable
Degree
19k
Software
Software
Systems
Software
Systems
Software
Degree
Degree
Degree
Degree
HND
Degree
PABX engineering
Field engineers
Trials engineers
Systems test
TSO5 (radar or aerospace)
C.tv & video comms
Degree
HND/degree
HND/degree
HND
Degree/exp.
0703 31818
Data communications
C.Eng.
01-609 9913. Ref.R9AD

0925 573160
0522 688121
Acoustic/audio research
Non-destructive test
I.c. design and production
Degree
COMPUTER HARDWARE
Plessey
Romsey
Surrey
Southampton
Derby/Bristol
British Gas
Rolls-Royce
Basildon, Borehamwood
Bristol, Rochester
GEC Avionics
Hewlett-Packard
Topexpress
Racal
Salary
Design engineers
Design engineers
Design engineers (radar)
10-20k
COMPUTER SOFTWARE AND SYSTEMS

US bank
Cambridge
West Sussex
Gloucestershire
Chessington
Romsey
East Midlands
Bristol
Cambridge
Herts. & Essex
Bristol
Wells
Acorn
-
GEC Avionics
Racal
Plessey
Hewlett-Packard
Topexpress
Bendix
Thom -EMI
COMMUNICATIONS
Brighton
Maidenhead -based
British Telecom
BNR
Freephone 3027
Freephone 3277
Cheltenham
Accra, Ghana
GCHQ
Planet Electronics
0256 468551
152 College Road
engineer
engineer
engineers
engineers
engineers
engineers
Degree
Degree
Harrow, Middx HA1 1BH

British Gas
GENERAL ELECTRONICS
N. London Poly.
London
Warrington
UKAEA
Marconi
Lincoln/Wembley
University College
London WC
Plymouth
Wandel & Goltermann
SALES
Brighton
Midlands
British Telecom
Technician (optical fibres)

" (microprocessors)
0752 772773
Freephone 3027
Steve Cash, PER,
21 Marble Street
10-20k
14k
10-17k
-14-16k
13-20k
No tax
Accommod'n
12-15k
6.5-7.3k
Degree/HNC
Des. engrs (test & measure)
Degree
7.3-8.4k
7.3-9.9k
20k
PABX sales
Degree
13.6-15.5k
Sensors/control
5 fig.
Manchester
Micro. products (mgr)
Manchester
Center-File
08163 8466
Midlands/SE
FOCOM
Personnel Off., Focom

Systems, Severn Rd,
Leeds LS10 1BL
Defence (optical fibres)
01-235 6060
01-387 6667
0243 825011
0273 471271
04867 6891
0423 865641
01-500 1000
M/c tool readouts. Manager

Components/systems. Manager
Burgess Hill
S. Hampshire
Bognor Regis
West of London
N. Midlands/NW
Home Counties
Hainauft
Corby
Sangamo
GSPK
Gould
RS Components
SERVICING/MAINTENANCE
Croydon
C. Health Authority
Birmingham
Automobile Assoc.
Victoria
A. H. Hudson
London/S. Coast
Dataller
Jersey
London
Univ. Inst. of Ed.
Personnel Officer RS
Components Ltd,
Birchington Rd, Corby,
Northants NN17 9RS
01-684 6999 x 4318
0256 492971
01-828 3937
Dataller Computer Ser.
King St, Wigan WN1 1BT
0534 30289
01-636 1500 x 254
25k
HNC
22k
25k
Degree
Components
Components
P.c.bs (area manager)
Instruments
Opto and instrument mktg
Electro-med. servicing
Radio maintenance
Dictatiori equipment
Servicing
PCs/home computers
Microprocessors
10-14k
12-20k.
Prey. exp.
Deg. pref.
4.5 day week
1020k
11k
ONC
C&G Fin.
7.3-9.3k
8.5k
8.5k
9k
8-9k
113
Appointments
Advertisements
accepted up to
12 noon November 3
for December issue
DISPLAYED APPOINTMENTS VACANT: 23 per single col. centimetre (min. 3cm).

LINE advertisements (run on): 5 per line, minimum 40 (prepayable).
BOX NUMBERS: 11 extra. (Replies should be addressed to the Box Number in the
advertisement, c/o Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS).
PHONE: SUSAN PLATTS, 01-6613033 (DIRECT LINE)
Cheques and Postal Orders payable to BUSINESS PRESS INTERNATIONAL LTD. and crossed.
JOBSEARCH TECHNOLOGY c
HARDWARE, SOFTWARE & SYSTEMS APPOINTMENTS
10,000 - 30,000
%
eFi
With the most successful companies and consultancies - both large and small - throughout the UK & Europe: Offering first class salary/benefit packages
(several include co. car) with excellent career advancement opportunities.
-
Experience in any of these fields would bB a particular plus:
HIGH SPEED SIGNAL PROCESSING: REAL-TIME 16/32BIT, ARRAY, PIPELINE OR BIT SLICE ARCHITECTURES; SOFTWARE - C, PASCAL; ADA;
ASM-VMS/UNIX etc: A I & EXPERT SYSTEMS: IMAGE & GRAPHICS PROCESSING: LASER/FIBRE-OPTICS: SONAR: RADAR: COMMUNICATIONS:
CUSTOM VLSI DESIGN: ANALOG/RF CIRCUIT DESIGN.
ECM offers confidential and professional guidance: we will listen to your requirements and identify opportunities to suit your plans. Phone now for your
FREE CASSETTE "Jobsearch Technology" and hear how ECM can help you to develop your career.
Call ECM on 0638 742244 - until 8.00 p.m. most evenings - or send your cv (no stamp needed) to:
ELECTRONIC COMPUTER AND MANAGEMENT APPOINTMENTS LIMITED

FREEPOST, BURWELL, CAMBRIDGE, CB5 8BR.
%1111111111matuar
Assistant
Test Manager
c12,500 p.a.
As leaders in the defence industry, our client currently
has a position vacant at their site in North West Surrey for an
Assistant Test Manager.
Reporting to the Test Manager, you will be responsible
for controlling the day to day running of the production test area,
which will include diagnoses of complex faults to component
level, liaison with internal technical staff and external customers,
and the supervision of a number of test engineers to meet
production programmes.
The successful applicant should be educated to at
least HNC level or equivalent, ideally in Electronics. Your
background must include a minimum of two years experience at
Test Engineer level, preferably in a supervisory capacity. The
ability to react to deadlines and work under pressure is essential,
and experience of Automatic Test Equipment/Software would
be a definite advantage.
Our client offers an excellent benefits package, including
relocation where appropriate and overtime will be available.
Applications will also be welcomed from less experienced
candidates, as more junior positions exist within the department.
In the first instance, please telephone or write to
REF:09/67
L. J. Associates at the address below.
ENGINEERING
OPPORTUNITIES
NATIONW DE
Edinburgh (031) 226 5381

Leeds (0532) 580510
Manchester (061) 832 5856
Birmingham (021) 643 1994
Leicester (0533) 544193
Milton Keynes (0908) 666872
Bishop's Stortford (0279) 506464
London (01) 637 0781
Bristol (0272) 211035
Bracknell (0344) 481808
Maidstone (0622) 687171
Crawley (0293)
*EDINBURGH
[ P
*LEEDS
AMA"`NESTER
'IRMINGHAM.
LEICESTER
MILTON KEYNES
BISMOPSSFORrFORIZOMDON
ER/srmLS
BRacxNEue
514071Ai
NAEUTo E
Salaries 8,000 to 30,000 p.a.

As the UK's leading specialist sales and technical recruitment consultancy,
we provide a FREE service to engineers seeking a career move.
If you have experience in digital, analogue, microprocessor or
communications technologies (either hardware or software), ideally with a
recognised qualification, we have hundreds of vacancies throughout the
UK in R & D, Design, Manufacturing, Test, Service and Sales.
Call your nearest branch for more information or send

a comprehensive C.V. (no stamp required) to: -
Interviews are held direct with prospective employer
Associates
Euston House
LJ
lJ ASSOCIATES
81-103 Euston Street

London N W 1 2ET.
Tel: 01-388 5465.
Division of ATA Selection and Management Services Ltd

FREEPOST. Bishop's Stortford, Herts. CM23 2BR.
A
Transmitter Capital Projects
It seems we go
to any lengths to
satisfy our audience
Currently, the BBC has over 1,000 transmit-
ting stations throughout the United
Kingdom and overseas, and we are spending some 17 million each year in order to
extend that number and, at the same
time, update our current equipment.
It's an ambitious engineering programme which covers powers from 1 watt

to 500 kW, radio frequencies from LF up to
SHF and the latest digital transmission and
control techniques.
It involves our Transmitter Capital
Projects Department in virtually every
aspect of the planning, designing and
equipping of transmission facilities.
Such is the pace of this work, we have

opportunities for graduate, or graduate
calibre electronic engineers.
If you are newly -qualified, or have up to
2 years' experience, opportunities exist
withinour engineering teams handling one or more projects at a salary of
between 9,600 and 10,400 p.a., depend-
ing upon experience.
Alternatively, with more than 3 years'

experience, which must have included
project management responsibilities, you
could take charge of one of our projects at
a salary of between 11,270 and 14,000
p.a., depending upon experience.
In every case a background in RF,
analogue and digital techniques or
computerised control systems would be
an advantage and you must have a degree
or equivalent qualification in electronic

engineering, normal hearing and colour
vision.
You can expect to travel to transmitter

sites throughout the UK as a regular part
of your work. There will also be extensive
training in BBC technology and methods
of operation.
That's where you come in
i,
engineering
Making an Art of Technology
The rewards will be very competitive

and the benefits package will include
25 days' annual holiday plus public
holidays, pension scheme, excellent
recreational facilities and, under certain
circumstances, relocation expenses.
For further information and an appli-
cation form, please write, quoting
reference 86.E 4019/WW to:

Head of Engineering
and Technical Operations Recruitment,
BBC, PO Box 2BL, London W1A 2BL.
We are an equal opportunities employer.
115
O
ASSISTANT
COMPUTER
APPLICATION
ENGINEER
Design Group
SATELLITE
RECEPTION
RESEARCH
ASSISTANTS
BBC
Monitoring Service
CLIVEDEN
1. BROADCAST SYSTEMS
Analogue, digital and microprocessor
experience. Repair a wide range of studio
equipment.
The Design Group produces designs for electronic equipment

used throughout the BBC and employs a staff of about 60
professional engineers. Computers are being used increasingly in
the design process, for software development, modelling, circuit
synthesis and analysis, and for CAD. The Group's work covers the
field from studios to transmitters.
Continuing expansion of the Group's computer facilities has
created a vacancy in a small team playing a key role in the planning,
implementation, enhancement and support of this rapidly growing
area of activity.
Existing computer facilities to support CAE comprise a VAX
730, two microVAX II, an Ethernet local area network and
numerous IBM and DEC PCs. Current plans include the addition of
CAE workstations, and you will be expected to participate in the
integration of these new tools into the existing CAD facilities.
You should have an engineering or science degree or
equivalent, electronic design experience and an interest in
computer aided design. Micro- or mini -computer experience is
essential; knowledge of VAXNMS desirable. Training will be given
where necessary.
Salary, according to experience, will be in the range of
10,633-14,877. Pensionable post. Excellent Club and
restaurant facilities. Relocation expenses considered. Five weeks
annual leave.
For further information please contact David Kitson on
01-927 4059.
For application form contact (quote ref. 2204/WL and enclose
s.a.e.) BBC Appointments, London W1 A 1 AA. Tel. 01-927 5799.
With the advent of satellite communications, broadcasting and
news agency organisations are switching from conventional
means to satellites for their transmissions.
As a Satellite Reception Research Asssistant, you will be
involved in the Monitoring Service's work in this field and your duties
will include frequency scanning and the compilation of
transmission schedules.
Extensive experience in communications with C & G
intermediate Telecommunications Technicians Certificate or
equivalent qualification and a thorough grasp of satellite
communications are essential. Knowledge of major broadcasting
systems, familiarity with news agency transmissions and the ability
to recognise a range of languages an advantage.
Suitable applicants will be required to take written tests and
appointment will be subject to satisfactory hearing tests. Shift work
involved.
12,496 including shift allowance.
Salary 10,070
Relocation expenses considered
Write or telephone immediately for application form (enclosing
addressed, foolscap envelope) and quote ref. 2638/WL to Senior
Personnel Officer, BBC Monitoring Service, Caversham Park,
Reading, Berkshire RG4 8T7. Telephone: (0734) 472742 ext. 212.
We are an equal opportunities employer
THE UK's No.
LTD
Telephone now for our free lobs list

We have vacancies In all areas of the UK
Salaries to 15,000 pa
Nani
116
CAPITAL APPOINTMENTS LTD

76 WILLOUGHBY LANE, LONDON N17 OSF
aa Ma
li
OM
10,000+Car, Surrey.
4. TELECOMMUNICATIONS
Approvals Engineer to test and fault find
complex analogue, digital and
microprocessor circuits to set
specifications.
12,000, Hants.
5. AVIONICS
Technician/Engineer to design and support
analogue and digital device.
10,000, Middx.
6. DATACOMMS
Development test and repair of new
products. Hardware/software prototyping.
to 9,000, Hants.
Hundreds of other Electronic

and Computer vacancies to
15,000
Phone or write:
Roger Howard C.Eng. M.I.E.E. M.I.E.R.E.
CLIVEDEN RECRUITMENT
92 Broadway, Bracknell,
Berkshire RG12 1 AR
Tel: 0344 489489
ENGINEER - CTV AND VIDEO

COMMUNICATIONS: (Location:
Accra Ghana).
Planet Electronics Ltd is one of the West Africa's

leading CTV and Communications Companies. Recent
expansion has created a vacancy for a high grade
Engineer with a good experience of CTV and Video
Communications; some experience of RF would be of
considerable advantage.
Duties would include:
* Customer Consultation
t P revine and Installation Training Programmes
* Involvement in AssemblyWork.
Based at our Accra assembly plant, the successful

applicant should display a high level of management
initiative and the position should lead to a senior
position in the Company with participation in policy
and planning.
An attractive Tax -Free Salary will be negotiated,
furnished accommodation will be made available and
medical expenses will be the responsibility of the
company.
Annual paid leave of 30 days plus local holidays and

return air-fares will also be paid.
Please send C.V. for early London interview to:
Alec Allan,
Planet Electronics Ltd, 152-156 College Road

33d
Harrow, Middlesex HAI BH.
1
"THE VOICE OF PEACE" Radio

Station, situated in international
waters off Tel Aviv, urgently requires a
broadcast transmitter engineer to
maintain the transmitters on board.
Must be fully experienced in this field.
Please write for further informational,
giving full details of experience to `The
Voice of Peace", PO Box 4399, 13 Frug
Street, Tel Aviv, Israel. (Please incude
RADIO TECHNICIAN
ti fi
f
.
(24hours)
Support Engineer involved in the repair of

micro and digital based control systems.
LEEDS CITY COUNCIL

DEPARTMENT OF HIGHWAY ENGINEERING AND
TECHNICAL SERVICES
01 808 3050
9,000+Car, Surrey.
3. FIRE DETECTION EQUIPMENT
f ELECTRONICS AGENCY
you have HNC/TEC or higher qualifications and are

looking for ajob in design, test, customer service, technical
sales or similar fields:
If
Repair and service marine and satellite

communications sytems.
your telephone number and code.)
i iii ii
r i i i i i iAPPOINTMENTS
CAPITAL
9,000, Herts.
2. RADIOCOMMS
2911
1
11/
Scale 5/6 8,391
331
- 10,164
Radio Technician is required for support of mobiles and base stations

throughout West Yorkshire. Based in Leeds, the successful candidate
should ideally hold a technical qualification in radio engineering or similar.
It is essential that candidates hold a current driving licence.
For further details contact Mr T. R. Endersby on Wakefield 367111
Extension 3534.
Application forms can be obtained by writing enclosing a S.A.E. to the
Personnel Officer, Department of Highways, Engineering and Technical
Services, Selectapost 6, Dudley House, Albion Street, Leeds LS2 8JX or
telephone Leeds 462761.
Closing date: 27th October, 1986.
Leeds is an equal opportunities employer.
Post suitable for job sharing.
A
339
BUSINESS
OPPORTUNITIES
NATO
UNIQUE OPPORTUNITY
Headquarters Allied Forces Central Europe
retail/wholesale/surplus
business established 30 years.
Valuable freehold site centre,
busy year round, south coast
town, stock, goodwill, site,
425,000. Directors retiring,
realistic valuation.
Candidates are sought for the civilian post of:
Principal Technician
(Quality Control)
Box No 311
WANTED
Nato Grade B-5

at HQ AFCENT, Brunssum, The Netherlands
WANTED
From the candidate it is expected that he has:

An overall knowledge of supply and logistics operations.
A firm grasp of computerized items accounting and stock management procedures.
An ability to write clear and concise instructions for local use, as well as an
abilty to
interpret and apply directives and policies established by higher authority.
Previous experience with supply management.
Test equipment, receivers,

valves, transmitters, com-
ponents, cable and
electronic scrap and quantity. Prompt service and

cash. Member of A.R.R.A.
M&BRADIO
86 Bishopsgate Street
Leeds LS1 48E1
0532 435649
Apart from the aforementioned essential qualifications, experience with military

supply
operations is desirable.
Applicants with a relevant higher vocational training, or equivalent qualifications
and
who meet the aforementioned requirements, are invited to obtain an application
form
and further information from the civilian personnel section headquarters AFCENT,
Post
Box 270, 6440 AG Brunssum, The Netherlands.
Completed application forms with c.v. must have reached the civilian personnel
section,
HQ AFCENT before the closing date, i.e. 28 November 1986.
The recruitment procedure may include a written test and interview
in which
background and experience will be questioned.
FRUSTRATED
ELECTRONICS
INVENTORS
Individuals or companies
Contact:
Mr G. R. Nicholson on
0242 578030
Professional Career Opportunities

The Easy Way to look for your new job from the
comfort of your own armchair. Our well qualified
consultants will carefully match your
requirements against
appropriate vacancies. ME
We have many clients seeking Engineers and Technicians at all levels

and we are
particularly interested in hearing from you if you have experience in
the following:
-
Real Time Software

Radar Systems
Technical Sales
RF Development
ADDRESS
ATE Programming
Technical Authorship
Your next step is to complete and return the attached coupon

or
telephone John Prodger on 0442 47311 or one of our duty consultants
on
0442 212650 during evenings or weekends.
POST CODE
TEL NO
EXe(IIll\Y' R('(;iiiifni('llt Services

THE INTERNATIONAL SPECIALISTS IN RECRUITMENT FOR
THE ELECTRONICS. COMPUTING AND DEFENCE INDUSTRIES/
Freepost, Hemel Hempstead. Herts., HP1 4BR.
QUALIFICATIONS
AGE
]
NONE
le
CG/HNC
DEGREE
OTHER
SALARY
(Mr/Miss/Mrs)
1.
JOE
WW
117
The Polytechnic
of North London
Faculty of Science & Technology
Re -advertisement
RESEARCH ASSISTANT
Research Assistant in Acoustics & Audio Engineering. The
work will involve theoretical investigation, computer
simulation and development of macro horn loaded ear
transducers. Applicants should hold an Honours Degree in
Electronic Engineering, Electronics with Physics,
Electrical Engineering or a similar area. Familiarity with
electro -mechanical transducer principles and analogies and
interests in acoustics or sound engineering would be an
advantage.
Further information obtainable from Dr R C Driscoll
01-607 2789 Ext 2166.
Salary: 6,579 - 7,362 (Inclusive of London Allowance).
Further details and an application form are

obtainable from The Personnel Office, The
Polytechnic of North London, Holloway Road,
London N.7., quoting ref. R9AD.
Telephone: 609 9913 (24 hour answerphone service).
UNIVERSITY COLLEGE LONDON
MRC RESEARCH ASSISTANT

Aids for the Totally and Profoundly Deaf
A physicist or engineer is needed to fill a Research Assistant post in a
multi -disciplinary team working on cochlear implants and acoustic
aids for the profoundly deaf. The MRC funded post is available now,
ending in July 1988 when the current programme grant expires, with
the possibility of renewal for a further five years. The collaborative
groups consist of workers in the Department of Phonetics and
Linguistics, University College London; the ENT and Physics
Departments, Guy's Hospital, London and the Department of
Experimental Psychology, University of Cambridge. The Research
Assistant, based in London, would work directly with patients and be
principally involved in the development of computer facilities (mini
and micro) for interactive assessment and in the hardware and
software development of signal processing hearing aids for the
totally and profoundly deaf. A background in micro -electronics,
materials science and computer programming would be desirable.
The appointment would be in the Grade 1B/1A scale, in the salary
range from 9,317 to 14,077, inclusive of 1,297 London Weighting.
For further details, please contact Prof. A. J. Fourcin,
Department of Phonetics and Linguistics, UCL, Wolfson
_House, 4 Stephenson Way, London NW1 1HE (tel. 01-387
1b55) or Dr. B. C. J. Moore, Department of Experimental
Psychology, University of Cambridge, Cambridge CB2 3EB
(tel. 0223 337733, ext. 3574).
333
ARTICLES FOR SALE
Closing date for the receipt of applications is 14 days from

the appearance of this advertisement.
THE POLYTECHNIC IS AN EQUAL OPPORTUNITIES EMPLOYER AND
THEREFORE PARTICULARLY WELCOMES APPLICATIONS FROM
WOMEN, ETHNIC MINORITIES AND THE DISABLED.
32
Radio Investigation Service

KEEPING THE WAVELENGTHS CLEAR
TELECOMMUNICATIONS
TECHNICAL OFFICER
TO MANUFACTURERS, WHOLESALERS
BULK BUYERS. ETC.
LARGE QUANTITIES OF RADIO. TV AND

ELECTRONIC COMPONENTS FOR DISPOSAL
SEMICONDUCTORS, all types, INTEGRATED CIRCUITS, TRANSISTORS,
DIODES, RECTIFIERS, THYRISTORS, etc. RESISTORS, C/F, M/F, W/W, etc.
CAPACITORS, SILVER MICA, POLYSTYRENE, C280, C296, DISC
CERAMICS, PLATE CERAMICS, etc.
ELECTROLYTIC CONDENSERS, SPEAKERS, CONNECTING WIRE, CABLES,
SCREENED WIRE, SCREWS, NUTS, CHOKES, TRANSFORMERS, etc.
ALL AT KNOCKOUT PRICES
Come and pay us a visit ALADDIN'S CAVE
TELEPHONE: 445 0749/445 2713
up to 10,000
R. HENSON LTD.
21
RADIO
TECHNICIANS
(5
minutes from Tally Ho Corner)
Surrey Ambulance Service
The Radio Investigation Service is part of the

Department of Trade and Industry's Radio
Regulatory Division. Its brief is simple - to keep
the wavelengths clear - of interference and illegal
Offers are invited for the purchase of a

Pye VHF/FM Radio Telephone System
147
dash -mounted
includes
which
mobile sets with three VHF fixed
stations, inclusive of vertical equipment
NOT
racks
and
board. Duplexers
included.
Contact to view: Mrs L Almeida at
Ambulance Service Headquarters, The
Surrey.
Horseshoe,
Banstead,
Telephone: Burgh Heath (073 73) 53333.
Tender forms from: Divisional Supplies,
Royal
Section,
Other
Commodities
Road,
Princes
Hospital,
Earlswood
Redhill, Surrey RH1 6JL.
335
DEPARTMENT OF TRADE & INDUSTRY
(1613)
EAST SURREY HEALTH AUTHORITY
up to 9,100
operators.
Right now we have a number of vacancies around
the country:
LONDON
From this London base, you will travel throughout
the UK, assisting in a variety of activities from the
investigation of radio interference to the evaluation
of monitoring, direction -finding and measurement
equipment.
CANTERBURY, WARRINGTON, LONDON
You will be responsible for helping to detect illegal
operators - collecting and presenting evidence for
prosecution - and for inspecting licensed operators,
ensuring that they comply with all relevant
regulations. In addition, you will investigate interference to authorised radio and TV services, and
advise on remedial action.
Candidates for the senior positions must be qualified
in radio telecommunications subjects to full TEC
Certificate level or equivalent, and have at least
4 years' radio technology experience. For the Radio
Technician posts you will need a relevant C&G
Intermediate Certificate and either 3 years' general
experience or 1 year in electronics/radio/TV.
Starting salaries depend on age, experience and
qualifications.
For more details and an application form, please
write with full CV to: Joan English, Department of
Trade and Industry, PRTU, Room 451, Sanctuary
Buildings, 16-20 Great Smith Street, London
SW1P 3DB, quoting reference E.88498. The
closing date for receipt of completed applications
will be: 14th November 1986.
115
Lodge Lane, North Finchley, London, N.12
E C COMPONENTS
We buy large and small parcels
of surplus I/C, transistors, capacitors and related electronic
stock. Immediate settlement.
Tel: 01-208 0766
Telex: 8814998
(2491)
G.W.M. RADIO LTD.
NOW AVAILABLE - Bumper

Catalogue - 170 pages - for collectors of
vintage radio, audio & TV equipment.
40/42 PORTLAND ROAD, WORTHING. SUSSEX.

Tel: 0903 34897
Eddystone EC1838/1 (Marconi Marine Atlantic) digital
readout 15 to 31MHz in 5 ranges USB'AM solid state
115/2305 AC supply, 19 inch rack mount. unused
condition quantity available 380 inc p&p. Also
Nebula EC958. Pacific EC1837 and Apollo receivers in
stock. G.E.C. mulimeters 30 inc p&p. Signal
generator advance type B4B directly calibrated from
30KHz to 30MHz 35 inc. Pye 460/461 UHF base 40
inc. Fantavox public-address Amps. 20 watts. 4-8 or
16 ohm OT 70 Volt line output 230V. AC. or 12V DC.
29 inc. p&p. Pye Bantam HP1 AM mid band,
example frequency TX 107MHz Rx 139MHz. Will mod
to air band sets only no mcs. or battery but with dry
337
battery tray 25 inc p&p.
Price: 2.00 post paid UK, 3.00 post

paid overseas. Vintage Wireless Co.
Ltd., Cossham Street, Mangotsfield,
Bristol BS17 3EN. Phone: 0272 565472.
(208)
CHEAP L.E.D. DISPLAYS. 7600

pieces, 0.3 inch, common anode, left
hand decimal, high light output,
standard red, industry standard pinout,
graded and colour coded, minimum
quantity 100. Price 20p each. Also lots
more cheap opto, fibre -optics etcetera.
Trade enquiries welcome. Ping: Ian at
Fibre-Data Limited on Tadley (07356)
77444.
(319)
QUANTITIES OF ELECTRONIC
COMPONENTS surplus to
requirements. Brand new. Eg 74LS244
= 40p. Tant Caps = 7p. Resistor
Networks = 12p. 24 Way Socket = 10p.
Also Disk Controller Boards
(1793+WD1691) + 40 TTL Chips,

Connectors, DIL Switches 9.00. SAE
for list: 15 Barcombe Road, Paignton,
Devon TQ3 1PZ.
338
When replying to
classified advertisements,
readers are recommended
to take steps to protect
their interest before
sending money
-I
SERVICES
ARTICLES FOR SALE
TIGOLLEDGE!
Ucrasomc hand-held generator:transducer-animal response

tests, alarms, converters, detectors etc. 25. Advance
sine/square generator 35. Ultrasonic detector, battery
operated, bats, whales. dolphins etc 89. Marconi Precision
multi -range meter 75. Elliott component curve tracer 85.
Low -range ohmmeter 45. Centrifuge 39. Crystal controlled
VHF Generator 49. Philips Transistor Analyser. Wave Energy
Systems Test -Meter 49. 16 Signal Generator 7.8 - l lcros
49. EMI & MSS disc cutting machines (collectors items) 75
ea. Pulse generator. Philips DC microvolts-volts meter 49.
Wayne-Kerr generator 55-100 MHz 69. Densitometer 35.
Stereo microscope High resolution microscope light Vacuum
diffusion pump 39. Vacuum dual pump unit 98. Chart
recorder Recorder pens. Technical books. Set of Tungsten
Taps & Dies 29. Battery Signal Generators lc/s - 1 MHz 69.
Oscilloscope Cable Fault locator 135 Wayne -Ken Signal
Generator 10Kc/s - 10MHz 49. Precision R&C Boxes. LCR
Bridge. Stabilised PSUs. Decade Precision Toroidal Matching
Transformer 45. Scope Probes. Aircraft Radio Test -Set 35.
Film Processor 69. Ignition Analyser 39. Kent Chromalog
2 Recorder 70. Pye Megohmmeter D3 - 200,000 Megohm.
Brandenburg 1000 & 1250 variable stabilised EHT Supplies
35.
Marconi Frequency
meter/counter/timer 69.
Phasemeter 69. Miniature High -Speed DC motors 1.75 ea.
Micro-Spot-Welding head 59. Pressure Gauges 4. NiCad
Auto
Charger E2080
25. Pure crystalline silicon
discs (Semiconductor applications) 1.50 ea. Multiphase
signal generator 89. Myron Conductivity Meter 35.
Sonatest Ultrasonic Probe 15. Vibration Analyser 75.
Strain -Gauge Meter 39. G -E High Power Stepper Motors
35 ea. etc etc
PCB'S MANUFACTURED.
ELECTRONIC DESIGN
OSCILLATORS AND FILTERS of

all types. Large stocks of standard
items. Specials supplied to order.
Personal and export orders welcomed SAE for lists please, OEM support thru:
design advice, prototype quantities,
Specialising in:
Lasers for industrial &
commercial applications
Power supplies including
linear H.V.
Electronic flash, also
measurement and industrial
control
Electronics, Merriott, Somerset YA16
PULSE PHOTONICS
'ELECTRONICS'
QUARTZ CRYSTALS
production schedules. Golledge

5NS. Tel: 0460 73718.
(2472)
Prototype, small/large production runs,

single, double -sided, P.T.H. screen
printing, panels, labels, solder masking
& photography. Orbitechnic Circuits,
The Rear of 127 Woodlands Road, Ilford,
Essex. Tel: 01-553 5211.
(154)
TURN YOUR SURPLUS i.cs

transistors etc. into cash, immediate
settlement. We also welcome the
opportunity to quote for complete
factory clearance. Contact COLES HARDING & CO, 103 South Brink,
Wisbech, Cambs. 0945 584188.
(92)
Box No: 336
IMPORTS/EXPORTS of all kinds of LTD, 299A Edgware Road, London W2
BRIDGES waveformn/transistor Electronics and Computers. Please send 1BB, England, or Telex 945922
analysers. Calibrators, Standards. your enquiry or product details to GLADEX-G for the attention of Mr.
Millivoltmeters. Dynamometers. KW DEDICATED MICROPROCESSORS C.Paps.
meters, Oscilloscopes. Recorders.

Signal generators - sweep, low
distortion, true RMS, audio, RM,
040-376236
deviation. Tel: 040 376236.
WANTED
(2616)
WANTED. EE8 American Field

Telephones, any condition, any
quantity. Phone: Monday -Friday, 9-
SERVICES
5pm. 01-743 0899.
324
CIRCOLEC
THE COMPLETE ELECTRONIC SERVICE
Artwork, Circuit Design, PCB Assembly, Test & Repair Service, Q.A.
Consultancy, Prototypes, Final Assembly. Full PCB Flow Soldering
Service.
Quality workmanship by professionals
economic prices.
Please telephone 01-646 5686 for advice or further details.
at
TEST EQUIPMENT
FOR SALE & WANTED
Buyers and Disposal Officers contact:
TAMWORTH MANOR
302-310 COMMONSIDE EAST, MITCHAM
COOKE INTERNATIONAL
11391)
ELECTRONIC SERVICES
CIRCUIT DESIGN, ARTWORK,
PCB ASSEMBLY. PROTOTYPES
For quality workmanship at economic prices
please telephone:
Unit 4. Fordingbridge Site

Main Road, Barnham.
Bognor Regis,
West Sussex P022 OEB
Tel: 0243 68 5111,2
WANTED GOLD PLATED SCRAP.

Best prices edge connectors boards etc.
Send smaple with no obligation to P & F
Turner & Sons, 9 Farndon Road, Oxford
OX2 6RS. Tel: Oxford (0865) 510293.
LOGICOMP
at 01-281 0633
(300)
STEWART OF READING
110 WYKEHAM ROAD
READING RG6 1PL
TEL NO: 0734 68041
TOP PRICES PAID FOR

ALL TYPES OF
SURPLUS TEST
EQUIPMENT,
COMPUTER
EQUIPMENT,
COMPONENTS etc.
ANY QUANTITY
WANTED
Test equipment,
computers. components.
Any quantity.
Good prices paid.
Immediate settlement.
Give us a ring.
Q-Teq Electronics
Unit 6, 28 Botley Road.
Hedge End, Southampton.
Tel: Botley 81487
(329)
CLASSIFIED ADVERTISEMENTS
Use this Form for your Sales
and Wants
PLEASE INSERT THE ADVERTISEMENT INDICATED ON FORM BELOW

To
"Wireless World" Classified Advertisement Dept., Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS
Rate 5 PER LINE. Average six words per line.
Minimum 40 (prepayable).
Name and address to be included in charge if
used in advertisement.
Box No. Allow two words plus 11.
Cheques, etc., payable to "Business Press
International Ltd." and cross "& Co." 15% VAT
to be added.
NAME
ADDRESS
REMITTANCE VALUE
PLEASE WRITE IN BLOCK LETTERS. CLASSIFICATION
ENCLOSED
NUMBER OF INSERTIONS
119
RANGE OF EQUIPMENT
SCOPES
tplADopg
i
'
HITACHIHAMEG
t4 ds
$
W,
sae
voucher
Seodlyt0?
ll'1
a+rw
q51Y
sa,,rY
,.,w,..
MULTIMETERS: SCOPES: CLAMPMETERS:

INSULATION TESTERS: WOW/FLUTTER
THANDAR
PLUS LOW COST RANGE
THANDAR BLACK STAR
POWER SUPPLIES
LARGE RANGE STOCKED
ECTR
f1ICS
74LSO4
74LS08
74LS14
6502
6522
74LS138
74LS139
74LS157
TL071
LM324
74LS240
74LS244
74LS245
1+
50+
.12
.12
.13
.17
3.30
3.30
2.80
2.80
.30
.30
.25
.25
.27
.30
.23
.50
.48
.50
.24
.26
.20
.42
.45
.43
1+
74LS273
74LS373
74LS374
74LS393
74LS541
8155
8251
8253
8255
6809
.46
.48
.48
.65
.45
1.50
1.50
1.50
1.50
3.80
1.40
1.50
6821
6850
74 HCOO
74 HC14
.25
.50
All memory prices are fluctuating daily,
PLUS COMPONENTS: TOOLS:

COMPUTER SOFTWARE AND
ACCESSORIES: SEMICONDUCTORS:
-Iu,;;
UT
OUOTE FOR
YOUR U
OUIREMENTS
DISCOUNTS FOR EDUCATIONAL,

TRAINING SCHEMES, ETC.
OFFICIAL ORDERS WELCOMED
OPEN
DAY SA
WEEK
(CIRCLE 32 FOR FURTHER DETAILS
S.M.C. 16
series of Eurocards which together form a very powerful microcomputer.

SMC 16 uses a 16 -bit databus memory expandable to 16 megabytes.
SMC 32 uses a 32 -bit databus memory expandable to 4,096 megabytes.
A
1+
2.10
2716
27C64
3.50
2.10
2764-250
2.40
27128-250
27256-250
3.90
1.30
1.30
6116LP-3
2.30
6264LP-15
1.30
0.90
4164-15
1.30
2.20
1.30
41256-15
1.40
280ACPU
3.50
1.50
1.25
280ACTC
11.00
1.25
65256AP
LM339
.25
.22
LM393
.35
.40
please phone to confirm prices.
50,
.42
.45
.45
.45
.35
83.95
(12.5 mHz 68000 & optional numerical processor
295.00
68881 co-processor for above board)
175.00
RAM 16 (1 megabyte dynamic RAM)
45.95
ROM 16 (1 megabyte eprom) no emproms supplied
69.95
I/O 16
(2 serial ports, 4 parallel ports)
N/A
SBP
)backplane 21 slot upgradeable to SMC 32 later)
N/A
PRO 16 (prototyping board for your own circuits)
VMP 32 (68020, 68881, 68851 virtual memory processor)
VMP 16 (available to order only, uses 16 or 32 bit databus)
85.95
DSK 16 (floppy & hard disk interface board)
CPU 16
50+
1.90
3.00
2.00
2.20
3.70
1.15
2.10
0.75
2.00
1.00
1.10
11.00
.20
.30
85.95
390.00
18.95
N/A
18.95
18.95
N/A
18.95
N/A
18.95
995.00
28.95
99.95
18.95
S.M.C. Electronics,
Unit 29, Portsmouth Enterprise Centre,
Quartermaine Road, Portsmouth P03 50T.
Tel No: 0705 478881 Telex No: 869455 Fax No: 673647
Please add 70p P&P and 15% VAT.
WIRELESS WORLD
N/A
199.95
55.95
Board
only
Other boards planned include colour graphics, RTC, A/D, D/A, Speech in/out and video interfaces.
Multi -tasking operating system available soon.
Minimum system CPU 16, ROM 16 (can use static RAMs), I/O 16, SBP 16 complete systems
supplied to order.
Brighton Road,
Purley, Surrey CR2 4HA
Tel: 01-668 7522
ELECTRONICS
Built
99.95
Kit
Description
178
&
00 00
TRANSISTOR CHECKERS. ETC.
1831
All items guaranteed to manufacturers spec.

Many other items available.
'Exclusive of V.A.T. and Post and Package'
.13
.13
.15
.19
R C GENERATORS:LCR BRIDGE.
DIGITAL CAPACITANCE: MULTIPLEXERS:
LOGIC ANALYSER: LOGIC PROBES:
301 Edgware Road, London W2 01-724 3564

404 Edgware Road, London W2 01-724 0323
EDUCATIONAL, EXPORT, TRADE
AND ACCOUNT ENQUIRIES. O1 25la
KESTREL ELECTRONIC
COMPONENTS LTD.
74LS00
METERS:DISTORTION METERS:FUNCTION
PULSE AND
COUNTERS: POWER SUPPLIES:
COUNTERS
BLACK STAR THANDAR

LEADER TRIO
THURLBY SOARPANTEC
SOh00\S
EflRY'S
'
I
TV TESTING: DIGITAL AND ANALOGUE
BECKMAN
INCLUDES
GENERATORS
MULTIMETERS
46PUK1
00.
l mrn12x9) e nd
\ oPoae
CROTECH
INDEX TO ADVERTISERS
Appointments Vacant Advertisements appear on pages 114-119
A B European Marketing
Advance Bryans Instruments

AEL Crystals Ltd
Air Link Transformers
Analogic Ltd
Arcom Control Systems Ltd
82
Bamber, B. Electronics
Barrie Electronics Ltd
Beronheath Ltd
40
39
BICC-Vero
75
Carston Electronics Ltd

Cavendish Automation Ltd
CIL Microsystems
Cirkit Holdings PLC
Coline International PLC
Communique (UK)
Computer Appreciation
Conguin Software
Control Universal
Cortex Controllers
Crotech Instruments Ltd
13
51
82
70
10
106
100
IBC
22
13
10
22
104
71
4
51
Dartington Frequency Standards... 109

5
Dataman Design
Dean Microsystems
Display Electronics
70
56/57
Electronic Brokers Ltd

IFC, 2, Advert Card, OBC
48
Electrovalue Ltd
29
EMS Mfg. Ltd
E&WW'Databank'
E& W W Edit Feature List
Field Electric Ltd
Fluke
GNC Design
Hameg Oscilloscopes
Happy Memories
Harris Electronics
Harrison Electronics
Hart Electronic Kits Ltd
Henry's Audio Electronics
Henson, R. Ltd
Hilomast Ltd
Ian P Kenloch Ltd
John's Radio
82
102,104
102
Advert Card
39
16, 29
g0
51
102
84
120
40
21
4
84
PAGE
PAGE
PAGE
PAGE
Kemitron Ltd
Kestral Electronic Components
80
120
Langrex Supplies Ltd

Levell Electronics Ltd
86
47
Marco Trading
Micro Concepts
92
40
6
Microkit Ltd
Micromake Electronics
MicroProcessing Engineering Ltd
Monolith Electronics Co Ltd
M S Component
13
47
4
82
Network Satellite Systems

Number One Systems Ltd
Panorama Antennas Ltd

Pineapple Software
PM Components Ltd
PSP
Quadrant Communications
84
29
112
40
110/111
82
21,92
Radiocode Clocks Ltd
Raedek Electronics
OVERSEAS ADVERTISEMENT AGENTS

France and Belgium: Pierre Mussard, 18-20 Place de la Madeleine, Paris 75008.
United States of America: Jay Feinman, Business Press International Ltd, 205 East 42nd Street, New York, NY 10017
- Telephone (212) 867
102
2080
Ralfe Electronics
Research Communications
Riscomp
RTT
92
21
109
Samsons (Electronics)
Stewart of Reading
Sherwood Data Systems
Silicon Glen
SMC Electronics
South Midlands Communication
Strumech Engineering Ltd
Surrey Electronics Ltd
100
Taylor Bros
Technomatic Ltd
Thanet Electronics
Thandar Electronics Ltd
Those Engineers
Thurlby Electronics
TIC Semiconductors
Triangle Digital Services
Valradio Power
Vine Micros
Webster Electronics
10
100
84
48
102
10
47
22
48
90/91
6
39
80
88
48
51
22
6
10
- Telex 23827.
Broadway, Wimbledon SW 19, for the proprietors, Business

Printed in Great Britain by Ben Johnson Printers Ltd, Oldhill, Dunstable, and t eset by Graphac Typesetting, Imperial House, 108 The
Business Press International 1986. Wireless World can be obtained from the following: AUSTRALIA and NEW
Press International, Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS.
&
Gotch
Ltd.
SOUTH AFRICA: Central News Agency Ltd; William
Ltd.,
Gordon
Service
ZEALAND; Gordon & Gotch Ltd. INDIA: A. H. Wheeler & Co. CANADA: The Wm, Dawson Subscription
Dawson & Sons (SA.) Ltd. UNITED STATES: Eastern News Distribution Inc., 14th Floor, 111 Eighth Avenue, New York, N.Y. 10011.
120
flIY1
_IEEE
Our PE
controller card
buy ore
L IEEE data
acquisition
instru
Wiy use dedicated cards
:or data
ecauisition wl-ich are noisy and
use va uable
card space? For unbeatable quality and value, buy

any CIL interface and you can get our IEEE control card
for only 150 extra! It enables you to use any other CIL data acquisition
IEEE instrument, with the extra advantages of on -board firmware to link
with the computer's language, and a watchdog for industrial applications.
32K RAM is available as an optional extra for IEEE data control.
MU
lTJ
m. s= m. rams.
E:: CA
sC s C iC s C
\:.%
1:.
MCIM
CZ!
mmm
mVIM
.t
IL
Microsystems Ltd
Decoy Road,
Worthing, W. Sussex, BN 14 8ND
Tel: Worthing (0903) 210626
Telex:878443 CIL G
s C s C sC
THE CHOICE FOR THE FUTURE
/,
2955 Radio Communications

Test Set 5,750
2382/80 Spectrum Analyser 13,150
and Display 5,350
test functions, including full duplex radio test

Revolutionary design: fast and easy to use
High clarity CRT shows all settings plus
measurements in digital or analog forms
Tones encode/decode facilities
38 instrument settings in non-volatile memory
Spin -wheel frequency/level control in addition to
front panel buttons
Single and two -port operation.
11
Audio to UHF coverages: 100Hz-400MHz

Outstanding resolution, with 3Hz minimum
resolution filter bandwidth

0.025dB amplitude resolution
Superb level accuracy IdB, with auto calibration
Frequency response better than 0.4dB
Fully GPIB programmable capability
Two steerable markers for levels and frequencies
Self calibration ti r repeatability of measurements.
2305 Modulation Meter 500kHz

to 2GHz 5,260
500kHz to 2GHz frequency range

Outstanding 0.5% basic accuracy
Exceptionally fast auto -tuning, with low noise
Modulation analysis including frequency and power
Non-volatile memory to store user settings
Excellent stereo separation
Automatic self -calibration, advanced diagnostics.
6960 Option 001 Digital RF

Power Meter 1,900
2022 AM/FM Signal Generator

10kHz to 1GHz 2,950
IS
Wide frequency cover: 10kHz to 1000MHz
Compact, rugged and lightweight

Comprehensive modulation: AM/FM/PhM
Simple push-button operation, large LCD display
Non-volatile memory for 100 settings
The perfect serviceimaimenmtcc tool
2440 Microwave Counter 20GHz
3,650
Sidiple push-button or systems application

Unparalleled accuracy, through sensor correction
Non-volatile storage of frequently -used settings
W or dB readings, plus offset capability
Single -key auto -zero operation
Average factor selection to reduce noise or improve
resolution, advanced GPIB facilities.
Wide frequency coverage: 10Hz to 20GHz

High sensitivity and resolution
Fast acquisition time: only 200ms typical
High -stability oven -controlled crystal oscillator
Overload capability up to 27dBm
High AM,FM tolerance
Built-in GPIB. CIRCLE FOR FURTHER DETAILS
through
ELECTRONIC
BROKERS
The first name test equipment distribution
Electronic Brokers are now

d_etributors for a fall range of Marconi
Test Instruments including Signal
Generators, Microwave Counters,
liver Meters, Moculation Meters,
Spectrum Analysers, RadioCommunicatidr Test Sets and other
general test and measuring equipment. For 'further information
and a colour brochure pler_,e contact our Sales Office.
b
onic Brokers
0
tl
in
3
1][
11
Electronic Brokers 140-146 Camden Street, London, NW1 9PB

MI: 01-267 7070 Telex: 298694 Fax: 01-267 7363
Ali
prices exclusive of VAT Prices correct at time of going to press (UKtely).'Ifadingcon

ittu-o:nai lab lcunrc
IICNI

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THE

looks backand forward

2955 Radio Communications

Wide frequency coverage:10 KHz to

2305 Modulation Meter

50 kHz to 2.3 GHz frequency range

PM6670/01 High resolution

PM 3055 50MHz Dual Time

variable readout speeds

HM 208 Digital Storage

IEEE interface fitted as standard

JF 37 Bench Portable OMM

Active video trigger for

Real time or digital storage to 20 MHz

PM 2534 Complete System

Real time to 20 MHz, storage

HM 208 Digital Storage Oscilloscope

JF 27 Ruggedized Hand -Held DMM

Dual trace and sweep delay

In-built component tester

3 /2 digit LCD with Bar graph

JF 51 Single Point Digital

Nin/Max and relative mode operation

77 Multifunction Hand -Held

JF 75 Full -feature analogue/

JF 73 Hand -Held DMM with

For the full stories, also latest news on

140/146 Camden Street, London NW1 9PB

CIRCLE.74 FOR FURTHER llETA1Ll;

VOLUME 92 NUMBER 1609

After ringing the bels in October, JW is now

In a similar process to that used in teletex,

Front cover is a solar prominence,

Second -user test equipment is often

MOBILE RADIO'S MANY

BROADCAST RADIO DATA

Mobile radio is one of the largest growth

Both IBA and BBC begin RDS next year.

WIDE AREA BINARY

BBC TELEVISION LOOKS

high -definition television, Pat Leggatt

ELEVEN YEARS IN THE

HEAT SINK SIMULATION

Using 68020 bus -size decoding as an

Hall -effect i.cs

Standard Eurocard bus - STE - is for small to -medium complexity systems.

VIDEO FRAME STORE

NEWS AND DIARY

81, 83, 85, 87, 89

our huge inventory

110(45710BU) 'The Portable'

Distortion Analyser P/In

Automatic Distortion Meter

Automatic Distortion Analyser

50MHz Pu se/Function Generator

HEWLETT PACKARD COMPUTERS

A large selection of 7000 series plug -ins available at up to

Contact us with yourrequirement2,

GENERAL PURPOSE T & M

SSG 520 + TTS 520 Transmission Test Set