SGBM INSTITUTE OF TECHNOLOGY

AND SCIENCE

JABALPUR

SESSION : 2018-19

VOCATIONAL TRAINING
REPORT

BACHELOR OF ENGINEERING
IN
ELECTRONICS & COMMUNICATION ENGINEERING

Submitted To
Prof. Sachin Singh (HOD)
Prof. Rashmi Mishra

Submitted By
KAMLESH KUMAR PATEL0216EC151005
B.E. (E.C.) Semester-7th
 DECLARATION

I hereby declare that the VOCATIONAL TRAINING in CONTROL

COMMUNICATION, RAIL NET, POWER SUPPLY SYSTEM &
EXCHANGE ON THE JABALPUR DIVISION OF WEST CENTRAL
RAILWAY whose report is being submitted in partialFulfillment of the Degree of
BACHELOR OF ENGINEERING in Electronics & Communication
Department of R.G.P.V., Bhopal, is the authentic record of my own work carried
under guidance of Mr. Susheel Namdeo DRM (S&T) Jabalpur, WCR. The matter
embodied in the report has not been submitted earlier for the award of degree.

Submitted By
KAMLESH KUMAR PATEL0216EC151005
B.E. (E.C.) Semester-7th
 ACKNOWLEDGEMENT

With a great pleasure and a sense of obligation, we express our heartfelt to

our guide Mr. Susheel Namdeo DRM (S&T) Jabalpur, WCR, I am highly thank
full to them for their individual guidance and support.
I would like to warm expression of thanks to all the members of staff of
ELECTRONICS & COMMUNICATION Department of SGBMITS, Jabalpur
and all those who provide me their valuable knowledge of subject CONTROL
COMMUNICATION, RAIL NET, POWER SUPPLY SYSTEM &
EXCHANGE ON THE JABALPUR DIVISION OF WEST CENTRAL
RAILWAY. The successful completion of trainingreport is not the result of hard
work of any single person but it is a cumulative outcome of number of Persons,
each having its own importance to the objectives. This section is to thanks and
gratitude towards those entire person who are directly or indirectly contributed in
their own special way towards the completion of the training report.

Submitted By
KAMLESH KUMAR PATEL0216EC151005
B.E. (E.C.) Semester-7th
 SGBM INSTITUTE OF TECHNOLOGY AND SCIENCE,
JABALPUR (M.P.)

Affiliated to Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal, (M.P.)

CERTIFICATE
This is to certify that the Kamlesh Kumar Patel ( 0216EC151005) is the
student of VII Semester in Electronics & Communication Department. The Report
of Vocational Training on CONTROL COMMUNICATION, RAIL NET, POWER
SUPPLY SYSTEM & EXCHANGE ON THE JABALPUR DIVISION OF WEST
CENTRAL RAILWAY being submitted is arecord of work done by him under my
guidance.

Prof. Rashmi Mishra

Guide

Countersigned By:

Prof. Sachin Singh Dr. P.S. Rana

H.O.D Principal

Electronic & Comm. Department

SGBMITS, Jabalpur

Date: Date
 RAJIV GANDHI PROUDYOGIKI VISHWAVIDYALAYA,
BHOPAL (M.P.)

CERTIFICATE

This is to certify that

KAMLESH KUMAR PATEL0216EC151005
Has successfully completed his Vocational Training on
CONTROL COMMUNICATION, RAIL NET, POWER SUPPLY SYSTEM
& EXCHANGE ON THE JABALPUR DIVISION OF WEST CENTRAL
RAILWAY.
During July 2018 in the partial fulfillment for the degree of
Bachelor of Engineering
In
Electronics & Communication Engineering

Internal Examiner External Examiner

 INTRODUCTION OF CONTROL COMMUNICATION

In Indian Railways different types of Telecom networks are exists and plays a vital role by
providing clear and distant voice and data services. Various types of telecommunication cables
with RDSO specification are being used depending upon the requirements of Telecom and safety
related Signalling circuits, which are under utilisation for functioning of administrative and train
operation activities.

Types of Telecomm Cables Used:-

Of the above cables mentioned , PIJF cable (05pr/10pr/20pr/50pr/100pr/200pr) are used for
outdoor and PVC Switch Board Cables for indoor are utilized for extending Telephone
connections to the subscriber premises.

The PVC insulation shall have distinct colour (Single colour or multicolour) for identification of
each conductor.

The colour of PVC insulation for the twisted pairs in the Switch Board cable is:
PIJF telephone cables are widely used in Railways for local loop and other networks due to
improved technology and simplicity in installation and maintenance. Indian Railway Standard
specification for Polythene insulated polythene sheathed jelly filled telephone. cable with Poly-
Al Moisture Barrier is IRS-TC: 41/97 (RDSO spec)
 Principles of Telephony

Telephony provides a means of sending information through human speeches when required
between two persons situated at a distance apart. In line telephony the information is sent
through the medium of line conductors between them.

Telephones: The apparatus that are used for transmitting and receiving speech signals are called
”Telephones” and the persons who use them for sending information between them are called
“Subscribers”.

The telephone transmitter and telephone receiver must be such that the conversion from speech
into electrical currents and vice-versa be perfect i.e. free from frequency distortion, amplitude
distortion.

Telephone exchange: It is a place where switching between two subscribers is done through
either manually or electronically. In addition to switching, signalling and controlling are also
done at “Exchange”.

Basics of switching

Before we delve into the subjects let us answer some basic questions on telecom switch.
A telecom switch has evolved from manual to mechanical to electromechanical thru’
electronic to digital.

An digital switch can either be space or time division or a combination of both. A present
day digital switch works mostly on what is known as the Pulse code modulation and use
the Time division multiplexing.

PCM and TDM forms the basic building block of any switching system. Keeping in mind
that the telephonic speech band is between 300 hz to 3.4 khz the following events takes
place when we want to transfer a signal from an inlet to an outlet:-

In a pulse code modulation the signal to be switched from the inlet to the outlet is
sampled as per Nyquist’s theorem which states that the sampling rate should be >/=
2wice the maximum frequency. The sampled signal is quantized and then coded .This
 is called digitization of the speech. At the output this signal is quantized and decoded
then filtered to get the actual waveform.

What will happen if we use this PAM signals to carry the voice sample from the inlet to the
outlet of the switching system?

• This PAM signal is susceptible to :-

• 1.Noise

• 2.Distortion

• 3.Cross talk

This amplitude susceptibility can be reduced or eliminated by converting the PAM signals into a
digital format thereby allowing the use of regenerative repeaters to remove transmission
imperfection before error results.

A finite number of bits are used for coding the PAM signals.

With n bits the number of sample values that can be represented will 2^n.

But the PAM sample amplitudes can take on an infinite range of values. Therefore it becomes
necessary to quantise the PAM signals to the nearest of a range of discrete amplitude signal.

BLOCK DIAGRAM OF PCM SYSTEM

WHY THERE IS NEED TO MULTIPLEX SEVERAL PCM SIGNALS?

As we have explained in earlier slides that the maximum frequency of telephonic speech is 3.4
KHZ. The sampling frequency should be more than or equal to 2wice the max frequency.

We choose the sampling frequency to be 2* 4khz(and not 3.4 Khz)=8 khz(because it is found
that at this frequency the signal can be reconstructed at the output.)

So each sample will take place in an interval of 8 KHZ which is 125 microseconds.

For a speech sample to travel from an inlet position to an outlet position it takes less than
5microseconds.

ISN’T THIS A SHEER WASTAGE OF THE AVAILABLE TIME SLOT ?

As a result of this, a switching element remains unused for more 120 microseconds if only one
sample is to pass from the inlet to the outlet. So if we can device a method by which a switching
element can be shared a number of inlet outlet pairs for a few microseconds each the entire time
duration of 125 microseconds is well utilized.

This is the principle of time division multiplexing.

Human speech and its transmission: Human speech consists of a large number of frequency
components of different values between 0.3 to 3.4 KHz having different mplitudes and different
phase relations between them.

Steps in Telephone transmission:

i) Conversion of speech into the electrical voice frequency currents at transmitting end.

ii) Transmission of speech currents through a media lines to the distant end.

iii) Conversion of voice frequency currents into speech sounds at the receiving end.
 Cables used in Telephony

In line telephony speech currents are carried by lines first into the exchange and there to the
receiver of the called subscriber through separate pair of lines. The type of transmission lines
used is generally insulated copper conductors, which are packed into a bunch of 10, 20, 50 or
100 pairs called as “Telephone cables”.

Copper wires are used for Telephony transmission due to, less attenuation and less distortion
provided that the insulation resistance of conductor is within the given values.

Basics of Telephone Exchange

Telephone Exchange is a place where switching between two subscribers is done through either
manually or electronically. In addition to switching, signalling and controlling are also done at
exchange.

It consists of the following functional blocks:

a) Main Distribution Frame with protective devices.

b) Card Frame.

c) Mother board.

d) Power supply panel with protective devices.

Main Distribution Frame (MDF): In a Telephone exchange different subscribers from different
places are terminated on a frame called “Main Distribution Frame” (MDF) in the exchange and
from there they are extended to subscriber’s line cards/Trunk cards kept in the exchange rack.
Protective devices are located in the MDF.

Card Frame: It contains different slots in which the nominated cards are to be inserted. It is
different in different types of exchanges.
Mother board: It provides connectivity between different cards. It is a multilayer PCB.

Power supply panel: It provides power supply to different cards in the exchange at different low
D.C. voltages. It also includes protective devices like fuses etc.
 Main functional areas in Telephone Exchange

a) Switching Function: The switching functions are carried out through the switching network,
which provides a temporary path for simultaneous, bi-directional speech between the following:-

 Two subscribers connected to the same exchange. This is called as “Local switching”
 Two subscribers connected to different exchanges. This is known as “Trunk switching”.
 Pairs of trunks towards different exchanges. This is known as “Transit switching” TCS1 -
Telephone Instruments

b) Signalling function: The signaling function enables various equipments in a network to

communicate with each other in order to establish and supervise the call. It is of two types,

i) Subscriber line signalling: It enables the exchange to identify calling subscriber’s line, extend
dial tone, receive the dialed digits, extend the ringing voltage to the called subscriber, extend the
ring back tone to the calling subscriber to indicate the called subscriber is being connected. In the
event the called subscriber is busy, engage tone is sent to the calling subscriber.

ii) Inter exchange signalling: It enables a call to be set up, supervised and cleared between
exchanges.

c) Controlling function: The controlling function performs the task of processing the signalling
information and controlling the operation of the switching network. The control functions may
be,--

i)Wired logic control: In this pre wiring is done between different speech path devices and
common control. If any changes are required in facilities of subscribers or introduction of new
services require wiring changes.

ii) Stored Program Control (SPC): After introduction of microprocessor, stored program control
system came into use. In this system the establishment and supervision of the connections in the
exchange is under the control of “Microprocessor”, which is suitably programmed.
 TELEPHONE INSTRUMENTS

Following are the types of telephone instruments used in Railways.

Push button Telephones: push button telephones uses a dial pad containing button to press
digits from 0 to 9 and special characters * and #.they comes in the variant of single line and
double line. A picture of line cord is shown below. it is a 2 wire line cord with RJ11 connector at
both end.

Main & Extension (1+1) type Telephones: these telephones are used to connect between boss
and secretary or may be between operator as a main phone and other users as extension.

Hand free Telephone with caller ID (CLIP phone): these telephones come with inbuilt
speaker to enable the user to talk without lifting the handset and to display the identity of the
caller, a display unit is also provided.

Two lines with speaker phone facility: these telephones come with 2 lines selectable. 2
different dial tones can be connected on it.

Two lines CLIP with speaker phone facility: as the name indicates these telephone instruments
are available with 2 lines terminated on it with hands free and caller identity display unit.

Cord less phone: these telephones come with a handset connected to base telephone by a radio
transmission. Uses trans-receiver frequencies for Trans and receive.
 DTMF Phone

DTMF means “Duel Tone Multi Frequency” signaling is used in telephony transmission

system Dual Tone Multifrequency System (DTMF)

DTMF is a system of signalling. Originally evolved for the transmission of dialling information
to automatic telephone exchanges from subscribers telephones. Its versality has lent itself
suitable for the transmission of impulses in the selective calling system used in Railway Control
circuits as well. In this system two tones of frequency within the voice band are sent out on line
corresponding to a given digit. Among the two frequencies one is a low frequency and the other
a high frequency both within the V.F.band. The transmission of the tones is so fast (typically in
multi seconds) that the signalling does not interfere with the speech at all.

Two tones which are harmonically unrelated are used; O/H line noise or line whistles
should not be recognized as signal. The tones are so chosen and recommended by CCITT that
minimum inter modulation occurs between each of the 16 possible tone pairs. One tone from the
low frequency group and one from the high frequency group are paired to mark the keyboard
output. The keypad is 4X4 or 5X5 matrix type, form as shown in the fig., since same
transmission medium such as the O/H lines and U/G cables. The frequency pairs are --
 TELEPHONE EXCHANGES IN INDIAN RAILWAYS

Indian Railways is the largest organization fulfilling the need of Passenger transportation and
goods transportation in our country. To facilitate the smooth and proper functioning of traffic,
real time information is communicated among various departments of Indian Railways. To
achieve this, Railways have its own communication system such as wireless communication,
optical fiber communication and land line communication for base telephones.

Exchanges in Indian Railways are providing communication between various functionaries such
as operating department, commercial department, engineering department, electrical department,
S&T department and so on.

Exchanges have been installed at All Zonal Head Quarters and Division Head Quarters.

Exchange is a switch which connects two subscribers in local exchange and as well as
connecting two subscribers on a trunk.

Exchanges are installed according to the requirement: such as,

 Number of subscribers
 Trunking between various Zones and division
 Services and features available for subscriber

In any Telephone Exchange, there are three functional areas, which can be identified as

1. Switching

2. Signalling

3. Controlling

Switching Function:

The switching functions are carried out through the switching network, which provides
temporary path for simultaneous bi-directional speech between:
  Two subscribers connected to the same exchange (Local Switching)
 Two subscribers connected to different exchanges (Trunk Switching)
 Pairs of trunks towards different exchanges (Transit Switching)

Signaling Function:

The Signaling function enables the various equipment in a network to communicate with each
other in order to establish and supervise the calls.

Controlling Function:

The controlling function performs the task of processing the signaling information and
controlling the operation of the switching network.
 Basics of SPC Exchanges

In SPC exchange, a processor is used to control the functions of the exchange. All the control
functions and the associated logic can be represented by a series of program instructions. These
instructions are stored in the memory of one or more processors, which control the operation of
the exchange. Control is dissociated from the switching network and is centralized in a number
of units on functional basis. Hence, the name Common Control Exchange arises for Electronic
Exchanges.

The processorof the exchange has to be shared by a large number of outside equipment such as
subscriber lines, junctions, Trunks, etc., and the tasks related to the establishment and
supervision of the various calls have to be performed 24 hours a day.

The processor contains program store and data Store.

Program Store contains all the instructions in their logical sequence used for the establishment
of the calls, for other Operational, Administrative and Maintenance purposes.

Data Store includes Translation Store and Call Store.

Translation Store contains the details related to the configuration of the exchange, Viz., number
of junctions, switch matrices, interconnection of these devices, data related to the subscriber and
the services provided, details regarding class of service, routing etc.

Call Store contains the details of progress of the calls. Provides temporary storage for transient
data required in processing the telephone calls such as digits dialed by the subscriber, busy/free
conditions of the trunk/subscriber lines etc. The information in the call stores keeps on
continuously changing with the origination and termination of calls.

Apart from the Central Processor, the Program and Data Stores, a number of peripheral
equipment also forms part of the SPC exchange. This peripheral equipment allows the processor
to communicate with the outside world.
For example,

Scanners check the change of state of the subscriber equipment and junctions periodically.

Distributors and Markers are used to convey orders sent by the processor to subscriber
equipment and switching matrices.
Functional Sub-divisions of a SPC Exchange
 ISDN Exchange

ISDN stands for “INTEGRATED SERVICES DIGITAL NETWORK”. Coral Flexicom 6000
Exchange is a ISDN Exchange. This exchange support all voice as well as Non-voice
information

Intergrated : all the three services are transmitted simultaneously on a single pair of wires.

Speech: 64Kbps

Image: 64Kbps

Data: 16Kbps

Total : 144Kbps

Services: Services to subscriber like transmission of speech, image and data.

Digital: the communication is digital up to subscriber’s instrument. But is also compatible,

through the transmission is in digital mode.

Network : Is a communication (arrangement) carrying system, including medium switching,

points and proper routing. Networks follow certain protocols (Set of Rules) for transmissions.

Establishment of a Local Call

The line-scanning program scans the subscriber's lines continuously and when a subscriber lifts
the handset, this event (off-hook) is sensed by the operation of the relay contact of the
appropriate line relay. In order to confirm that the off hook condition was not observed earlier,
the central control compares this with the result of the previous scanning cycle and concludes
that a request for connection has occurred and updates the status information for that particular
line as busy.

From the scanner address of the calling subscriber, the central control refers to the details about
the subscriber, stored in the translation stores. The central control then selects an idle digit
receiver and establishes a free path between the calling subscriber and the digit receiver, through
the mark and drive program. The identities of the originating Junction circuit and the digit
receiver are stored in the register-buffer.

The central control instructs the signal distributor to operate a relay in the digit receiver to send
dial tone to the calling subscriber. Digit receiver returns dial tone to the calling subscriber. The
digit receiver is only capable of detecting the dial pulses, but cannot count them. As soon as the
first digit pulse is received, dial tone is cut off. The calling line is scanned at every 10
milliseconds through another scanner to detect changes in the line conditions due to dial pulses.
The central control compares the present scanner reading with the previous one, Whenever
change is noticed and the line is offhook, the central control adds one to a pulse count kept in the
data stores of the particular line. When no change is detected for a period of at least 100
milliseconds, it is interpreted as an Inter digital pause. When the last digit has been received, the
dialed number is converted to a translation store address, where it finds the corresponding
translation information of the called line, which includes the called line's scanner address and
other details such as class of service, category, etc. The system now checks if the called line is
busy or free by looking at its busy-idle bit.

If the called line is free, the digit receiver is released from the calling line, the central control
now searches in the data store for a path to be used to establish conversation between the calling
and called subscriber, through the mark and drive program. When a free path is selected, the
identity of the selected terminating junction is stored, the path established and ringing phase
started. Central control instructs the signal distributor to apply ringing current on the called line.
When the called subscriber responds, ringing is tripped and speech path is established between
the calling and called subscribers.

The system now scans both sides at every 100 milliseconds for a possible disconnection, after
which the lines are restored to normal. Further, normal scanning to detect origination of new
calls is continued.

Some of the Exchanges which are used in Indian Railways are:

C-DOT Exchanges (128 port/256 port PABX)

IRIS- IVDX

Coral Flexicom series: Various series of coral Flexicom are available. Coral ISBX 5000,
Flexicom 6000, IPX 500 and IPX 3000

Siemens Hipath 4000 also used as Main Exchange.

Byte SDH 1000 Exchange used as intercom exchange within a building.

 Coral Flexicom-6000(ISDN Exchange)

Coral Flexicom-6000 series exchange is manufactured by Tadiran Telecom, ISRAEL. Fully

digital, ISDN compatible, VOIP support and distribution of 6000 port on the basis of Memory
allocation for physical as well as virtual ports in this exchange. This distribution is standardized
by a Size list default in the system design.

Some key points about this exchange:

1. Modular in design. (cards are modular)

2. Easy up gradation of hardware and software.

3. 512 timeslot processing from peripheral to control, those 4 times more than the normal
exchange.

4. Redundant control to enable hot standby feature in case of active copy failure. 5. Automatic
hardware detection in a slot.

6. Remote access to the system through dial up modem

7. Various features for subscribers, trunks and Tenant groups.

8. Easy partitioning of exchange on the basis of class of services.

9. Full back up support

Hardware: it includes Peripheral cards, service cards and control cards

Peripheral cards:

 24 SA/24 SLS 24 port analog subscriber card

 24 SFT/24 SDT 24 port digital subscriber card
 PRI 30 30 voice channel multiplexed= one digital signalling channel, which works on
QSig protocol
 30 CEPT 30 voice channel for communication works on MFC signaling protocol.
  4TEM 4 port E&M (2 wire/ 4 wire) trunk
 8T-C 8 port CO trunk card (2 wire)

Service cards:

 iDSP identity display card

 8DRCF digital resources and CONF card
 8DTR DTMF Trans receive card
 CONF 8 no of 3 way/ 2 multi party Conferences 15 party in each.
 TADIRAN TECHNOLOGY ISDN EXCHANGE – CORAL FLEXICOM 6000

Coral Flexicom6000 developed by Tadiran Telecom of ISRAEL with High traffic handling
Processor for large businesses needing 6000 Ports.

 The main elements in the Coral Flexicom 6000 system are as follows:

 Two sets of control cards providing two fully functional sets of control systems

 Proprietary Mirrored Memory and Switching Matrix technology built into the circuitry

 Programming software

 A motherboard supporting two sets of control systems

 Dual peripheral buffer units

 Dual power supply units

 The operating software stored in the CFD (Compact Flash memory Disk) of both control
system sets,

 Database program is stored in battery-protected SRAM in the appropriate components of

both control system sets.

 All generated data stored in the memory of the “Active” control system is automatically
recreated in the corresponding component in the “Standby” control system, ensuring
rapid and seamless system changeover, fail-safe storage, and database dependability

 In the event that the second or “Standby” control system must take over control, all
communications activities continue unobstructed as if a single system has been in control
all along.

Coral Flexicom 6000 builds on a proven free-standing, floor mount main cabinet, serving
as the system’s foundation. Each system consists of one Main cabinet, which houses the Coral
Flexicom 6000 Control Shelf and Peripheral Shelves and one or more optional Expansion
cabinets.

Coral Flexicom operation is supervised by highly efficient, stimuli controlled call

management Software with a 32 bit main processor INTEL 80386, hierarchical processor
located in every peripheral card and in every digital telephone set. System of distributed
processing is Utilized for efficient working. Operating software is stored in flash ROM.

The system employs Universal Card Slot Concept, i.e., any peripheral interface card slot
can accept any peripheral card without sacrifying the system capacity. The slots are self
programmable by default as per the cord introduced. Even the ports are self programmable by
default, according to the type of card kept in the slot. Dual Linear Serial bus design is used to
carry the control, voice, data signals through out the system. Every signal is assured alternate
route within system.

Control Shelf and Control Card

Control Shelf is positioned at the bottom of the main cabinet. The Control Shelf is built to
provide two sets of slots for the components required for the two common control systems. The
Control Shelf is divided in half to provide corresponding slots on the Left and Right sides for
each set of control system components to reside.

Each side consists of the following card slots placed in the order from the middle outward:

 16GC or 32GC (+SAU)

 CLA-ATS (Optional)
 FMSD (for CLA-ATS Optional)
 MCP-ATS
 Coral Flexicom 6000 system 4 shelf configuration

The MCP-ATS is the main control processor of the Coral Flexicom 6000 system. It contains the
main control processor circuitry and Memory Management circuitry, and utilizes a powerful
Pentium microprocessor with PC architecture, which connects to a Compact PCI compliant
backplane. The MCP-ATS includes 64 MB RAM. MCP-ATS card is accompanied by a 64MB
FMSD (Flash Memory Storage Device).Main Control card, includes a flash disc of 128 MB with
default configuration, routing, number plan of the exchange.
The 32GC Group Controller card is the heart of the Coral FlexiCom 6000 system.It serves as a
communication link in the Coral FlexiCom 6000 system, between the control cards and the
PBATS cards located in peripheral shelves. Each of the dual control system sets contains one
32GC card. Each 32GC card includes innovative proprietary mirrored memory and switching
technology essential to the Hot Standby system. 32 GC Group Control card, connecting 16
peripheral shelves for inter peripheral switching, includes a Software Authorization Unit.

Software Authorisation Unit (SAU): Provides a unique system for installation at site. During
software installations, the SAU identification number is compared with the authorisation data. If
SAU is removed the system shall work up to 14 days. It is plugged into the front panel connector
of the 32GC card in each of the control card sets. Each SAU contains a unique system
identification serial number. Each SAU unit contains a set of permissions associated with its
unique identification number.

SAU contains all the Licenses for hardware and software in it.

PPS card (Peripheral Power Supply Card) :

 Peripheral Power Supply card

The PPS provides internal operating voltage for switching systems. It controls 3 pulse
width modulated switch mode dc/dc converters, which convert -48v to +5v, -5v, +12v, -12v
operating voltages for internal circuits. Each PPS can support 2 peripheral shelves. An ON/OFF
switch, input fuses, power On LED indicator, Test points and adjustment terminals are provided
on this

card.
Ringing Generator Power Supply Unit (RPS):

The RPS provides high voltage ring generator current required by line telephone station ports. It
contains a low frequency oscillator and power amplifier, which converts -48 V DC into 75 / 85 /
105 V AC at 16 / 20 / 25 Hz for use as ringing voltage. An ON /OFF switch, input / output fuses,
test points, voltage adjustment points, frequency select switch is provided on the front panel of
the card. Each peripheral shelf is provided with independent RPS card, which Should be
removed only in power OFF condition.

Subscriber cards are of two types. They are as follows:-

a) Two Wire Standard Single Line Station Interface (24 SLS):

It contains 24 sub ports. It contains 2-wire loop start circuit for analog telephone
connections. Similarly 16 SLS and 8 SLS are also available. Number 24/16/8 shows the number
of circuit made available for use.

b) Two Wire Digital Station Interface (24 SDT):

24 Digital telephone circuits which supports DKT and DST service telephones.

Following at the list of trunk cards, used to connect with other exchanges:--

a) 30 Channel Digital Trunk Interface (30 T):

The 30T card provides E1 digital interface which multiplexes 30 trunk channels into
single 4 wire digital circuit operating at a data rate of 2 Mbps.

b) 2 / 4 Wire Inter-Exchange Tie Trunk Interface (4TEM/S):

The 4TEM/S card contains four identical circuits which provide E&M trunk circuits Each
circuit individually configurable with two wire or four wire.

c) ISDN Primary Rate Interface Card (30 PRI):

This card is used for connecting with distant ISDN exchanges for extending full ISDN
capability transmission to the distant exchange. It contains 3OB + 1 D channels.

d) 8TC card ( Central Office Card):

This card provides 8 nos of channels for trunk connectivity.
 Service Cards:

The system may be equipped with one or more shared service cards, which provide functions
such as dial, call progress detection, DTMF, MFC tone dialling reception, multi party conference
etc.

8 DRCM:

This is a new card containing many features as follows:

DTD - Dial Tone Detector.

DTR - Dial Tone Receiver.

RMI - Remote Maintenance interface.

3 Way Conference.

6 Way Conference.

DTMF working

Music on hold.

RS 232 C data ports for data base programming

These cards are to be removed with Power off condition.

DTMF Signalling Receiver Circuit (8DTR):

8 DTR card provides 8 circuits which receive and decode dual tone multi frequency
dialling tones.

Multi Party Conference Bridge Unit (CNF):

CNF card provides either multiparty conference or 3 way service but does not provide
both. It
provides,

8 circuits of 3 way conference

2 circuits of 15 way conference

1 circuit of 30 way conference

PB-ATS PB (Peripheral Buffer) card, for Coral FlexiCom 6000. Buffers PCM streamsand
HDLC highway, Clock and Sync signals to the Peripheral Shelves.Installed in even numbered
Peripheral Shelf. It acts as a signal regenerator for the peripheral highways. A single PB-ATS
card provides the full range of exchanges between the 32GC card and the peripheral bus serving
the peripheral shelves.

iDSP 64 circuit FSK (Frequency Shift Keying) tone generator card. The card converts ASCII
text information, received from the Coral main processor, into FSK tone: The FSK tones are
supplied for direct injection onto the Coral PCM highways. The card provides up to 64
individual FSK tones simultaneously, each on a different PCM channel and call. The iDSP card
is required for displaying CID (Caller ID) for SLT users.
 NMS( NETWORK MANAGEMENT SYSTEM)

This is the software part utilized for day to day maintenance regarding creating, deleting,
activation of any feature to any subscriber etc. Generally, HyperTerminal software available in
Windows XP edition is used. Free software like Putty can also be used for programming
purpose.

Few commands used for maintenance work are as follows:--

i) PLIS (Port List)

Through this command exact port details can be seen, were any subscriber number is
been created in the telephone exchange. This command also facilitates to display any number by
its designation.

ii) CLIS (Card List)

This command helps to display card position in any shelf as well as the status of the card
( whether active or out-of-service). This command is also used to configure any new card
at any new slot in the exchange.

iii) SLT (SINGLE LINE TELEPHONE)

This command used to set parameter of any analog telephone as per requirement.

iv) KEY
 This command used to modify parameters of Digital key telephones as per requirement.

v) PROG (PROGRAMMING OF DKT)

This command is used for programming of speed dialling button available at Digital Key
Telephones.

vi) FEAT (Features)

This command used for activation / de-activation of feature from list of features for any
susbscriber (i.e., analog as well as digital subscriber).

vii) NPL (NUMBER PLAN)

Above command used to CREATE/MODIFY/DELETE any new number in the

exchange.

viii) TKGP (TRUNK GROUP)

Command used to program new trunk that is to be connected to other exchange, for
connectivity between two exchanges.
 POWER SUPPLY SYSTEM & EXCHANGE

Power supply arrangements are required at different offices for different types of
telecommunication equipments for better working without interruption.

PROTECTION LEVELS

There are four types of protections utilized in connection with Telephone Exchange: --

a) Class A

b) Class B

c) Class C and

d) Class D protection.

Class “A” protection: Protection against the lightning on the structure housing the equipments.

This is provided with an external lightning conductor on top of the building connected
through a down conductor to ground (Earth). This is known as Class A protection. By this
arrangement 50% of lightning energy connected to ground. Depending on the area, size of the
structure to be protected, the type of protection varies.

Class “B” protection:

The first stage for protection provided before the equipment at mains distribution panel is
called Class B type protection.

These are spark gap type operates on arc chopping principle and designed to handle
lightning current pulses of 10/350micro sec. the sealed type should be used near places having
explosive gasses like gasoline. Maximum operating voltage 1.1 times nominal supply voltage.
The voltage protection/clamping should be as less than 1.5KV. Its response time should be less
than 200 nano seconds.

Class “C” protection:

An Metal Oxide Varistors (MOV) is provided between phase and Neutral and has a surge
rating of 50KA 8/20Micro sec. this should be as single compact device of proper rating and in no
case a number of varistors should be provided in parallel. This device should have following
additional features:

1) Indication to show health of the device which should turn red when failed

2) Thermal disconnection to the arrester when it starts having heavy leakage current due
to ageing after handling repeated surges.

3) Potential free contact for remote monitoring

Provision of one set of Class “B” and “C” devices is must.

Class “D” protection

It consists of a combination of MOV’S and GD tube. This should have all the features as
mentioned above for Class C devices. All external data/ signaling (as/dc) lines connected to
electronic equipment should be protected by this arrangement.

One exception where Class “D” devices should not be provided is the cable conductors
carrying signal lightening fed as leakage in MOV’S due to ageing will have adverse effect on
working.
 Here we will discuss above power supply arrangement setup at Telephone Exchange.
Coral Flexicom 6000 exchange operated at input voltage of -48V DC.

The ac power hum due to ripple current in the output of a battery charger is to be
avoided. This can be achieved by running the equipment only on battery without charger
connected to the equipment directly. This can be done by providing charge- discharge working.

In this TWO battery banks are used. If one battery bank is under charging and the other is
connected to the equipment. Connection and disconnection of the equipment and batteries are
done by the DPDT/DPST switches as shown in the wiring diagram.

A suitable type of battery charger is to be provided to charge the battery banks. While
changing over the batteries precaution to be taken not to switch off the equipments. For that put
both the DPDT switches to UP side and then put the required switch to DOWN for charging
battery.
 BLOCK DIAGRAM OF POWER SUPPLY ARRAGEMENT

(AT MAIN DIVISIONAL EXCHANGE)

The electronic exchange requires 48V±4V DC. This can be provided with a battery of 48V DC
with 24 cells connected in series. The capacity of the battery can be calculated taking the current
drawn by the equipment. A battery charger of suitable type with required current rating which
can charge the battery and supply current to the load should be used.

Here is how to calculate the capacity of the battery bank that is to be used for uninterrupted
power supply (DC Volt) to telephone exchange.
Example: ---

Current drawn by the 128 port electronic exchange- 3 Amps.

Capacity of the battery required is – 3A X 10 H = 30 AH.

(H stands for Hour and A stands for current drawn)

But as for the RDSO the battery should not be discharged to 50% of its Capacity to get
maximum life from it. So the Capacity of the battery required is double to that of the calculated
value. Which becomes 2 X30 = 60 AH.

So we can go for a 80 AH battery and above.

Here at Main Divisional Exchange, Two numbers of Battery Bank of each 500AH capacity is
used. Having each Cell voltage of 2.20V. Of make AMAR RAJA and MICTROTEX
respectively.

Battery charger used are of “STATCON” make of SMPS type. With 4+1 SMR module.
Each SMR module is of 25A .battery charger has 02 nos of battery charging connections and 01
nos of load point.