AU691182B2 - Loading coil device - Google Patents

Description

Rcgulition 32

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

o Name of Applicant: Address for Service: Invention Title: TELSTRA CORPORATION LIMITED DAVIES COLLISON CAVE, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

LOADING COIL DEVICE The following statement is a full descripion of this invention, including the best method of performing it known to me/us: -1- -2- LOADING COIL DEVICE This invention relates to a loading coil device and electrical surge protection device.

In communications systems, there arises a need for electrically loading communications lines for the purpose of providing more satisfactory electrical performance. In particular, where communications lines are long, capacitive or other effects between a cable pair making up a line may be such that distortionless transmission i 10 along the line is impaired. Such impairment may be compensated for, at least to some extent, by the provision of some electrical impedance associated with the line, such as between conductors of a cable pair making up the line, and positioned at a suitable location relative to the length of the line. Most commonly, what is required is to place lumped inductances, or load coils, at spaced locations along the length of the lint. The use of loading coils was first proposed by Michael Pupin in United States patent Nos.

652230 and 652231. A historical review of loading coils is contained in the publication "The evolution of inductive loading for Bell system telephone facilities" by Thomas Shaw, The Bell System Technical Journal, Volume 30, January 1951, pages 149-204.

A fuller description of the considerations involved in this is contained in the publication "Engineering and operations in the Bell system" 1982 Edition, Bell Telephone Laboratories Inc., particularly at chapter 10 thereof.

To ensure distortionless transmission, the attenuation constant should be constant with frequency and the phase constant should be proportional to the frequency. The addition of load coils along a line changes the attenuation characteristics of the line.

Typically, the effect of adding the loading coils is that the attenuation in the line is constant with frequency up to a cut-off frequency of approximately 3.4 kHz. That is, the communications line functions as a low pass filter.

Normally, numerous cable pairs are run together in communications installations, within a single sheath for example, and where loading coils are to be employed, a number of these, one for each cable pair may be provided at a single location such as within a 94706,p:\opeircm,tIcastrl1.spc,2 P 0' MIl t4712A *0 13 1 ;3 -3sealed canister and with associated fly lead tail cable which enable the individual cable pairs to be connected to individual coils. If some of the coils in the canister deteriorate or are damaged by lightning surges, then the whole canister needs to be replaced.

According to the present invention there is provided a loading coil device comprising a printed circuit board on which are positioned a plurality of loading coils and an electrical connector, ends of the coils being connected to contacts of the connector via conductive tracks on the printed circuit board, the contacts being of a kind permitting the making of an electrical connection to an insulated wire by pressing the insulated wire between an i 10 electrically conductive element such that the insulation of the conductor is cut by at least one edge and electrical contact made between the wire and the at least one edge.

The invention also provides a telecommunications system including a plurality of cable pairs for carrying telecommunications signals, which pairs are electrically loaded by a loading coil device comprising a printed circuit board on which are positioned a plurality of loading coils and an electrical connector, ends of the coils being connected to contacts of the connector, via conductive tracks on the printed circuit board, the contacts being a kind permitting the making of an electrical connection to an insulated wire by pressing the insulated wire between an electrically conductive element such that the insulation of the conductor is cut by at least one edge and electrical contact made between the wire and the at least one edge, wherein conductors at adjacent ends of cables of each of the plurality of cable pairs are coupled to a respective loading coil by connection to contacts of said connector. In a particular form of the invention, the loading coil device is located in a housing to which the cables enter to be connected to the connector. This arrangement avoids the need for connections between the ends of the conductors and the fly leads of a canister incorporating the loading coils.

'J

Zrf -4- The invention is further described by way of example only with reference to the accompanying drawings in which: Figure 1 is a perspective view of a loading coil device constructed in accordance with the invention, fitted with an electrical surge protection device; Figure 2 is a perspective view of the loading coil device and protection device of Figure 1 with the protection device removed; Figure 3 is a plan view of the loading coil device; Figure 4 is a schematic view of the electrical circuit presented by the loading coil device in use; Figure 5 is a schematic view showing the interconnections of the protection device in use; Figure 6 is a perspective view of the electrical surge protection device; Figure 7 is a diagrammatic representation of a conventional loading coil arrangement; Figure 8 is a diagram of a loading coil arrangement according to the invention, in situ; Figure 9 is an underside view of a circuit board forming part of the loading coil B device Figure 10 is a perspective view of an open housing, as seen in Figure 8, and containing load coil devices formed in accordance with the invention; and Figures 11 and 12 are opposite side views of a circuit board incorporated into the electrical surge protection device of Figure 6.

Referring firstly to Figures 1 and 2, the loading coil device 10 shown comprises a circuit board 12 of generally elongate rectangular form having on one side thereof (Figure 9) conductive tracks 110 for interconnecting loading coils 14 mounted on the circuit board with contacts of an electrical connector 16 also mounted on the circuit board. The coils 14 may be of conventional form, having a wire coil the ends of which are connected to tracks of the circuit board 12 by suitable means such as soldering. The connector 16 may also be of conventional form, such as being a connector sold under the brand name "Krone", being in the form of an elongate plastics moulding with two opposed rows of upstanding posts between each adjacent pair of posts in a row there 9407K6p.opecm,teIstrI1.spc,4 being mounted an electrically conductive contact element which has an upwardly open slot so configured as to enable an electrical connection to be made to the contact element by passing an insulated conductor downwardly into a slot such that the insulation is cut by side edges of the slot and opposed side surfaces of the conductor are brought into contact with the edges of the slot.

In the particular arrangement shown, there are ten coils 14 arranged adjacent longer side edges of the circuit board, with the connector 16 extending also parallel to the longer edges of the circuit board and between the two rows of the coils. It has been 10 found convenient to interconnect one end of each coil with a contact element of the connector 16 in the row thereof at one side of the connector 16 and the other end of the coil to a corresponding, opposed, contact element in the other row of the contact elements provided on the connector. By this, it is easily possible to identify one side of the device as an "exchange" side and the other side as a "country" side. By these terms are meant that the connections to be made to coils, from ends of cable pairs coming from a telephone exchange, are made to the "exchange" side of the connector, and connections to cable pairs at ends of cables going in the direction away from the exchange are made at the other or "country" side of the colmector.

Thus, to use the loading coil device 10, a cable is cut at a suitable location along :the length thereof and ends of the conductors produced at the exchange side are terminated as described at the exchange side of the connector 16 and ends of the conductors produced at the country side are made to the country side of the connector.

These connections may be also made as described by inserting the conductors into the aforementioned slotted connector elements of the connector 16.

The resultant circuitry is shown at Figure 4 where there is shown, in this case, a variant of the form of device shown in Figure 1, where there are twenty coils 14, this simply representing an arrangement where the device is twice as long as the device shown in Figures 1 and 2 with ten coils 14 to either side and having two connectors 16 arranged end to end. Here, cable pairs identified as "cable pair No. "cable pair No.

are shown together with terminations to each of the coils 14, designated T1 T20 at 94O706,p:\opccm,testr11xpc.5 I I -6connection points Xl(in) and Xl(out) as well as X2(in) and X2(out), being terminations made at the connector elements of the connector 16.

The loading coil device 10 offers three main advantages over the normal canister style device distinct from the potential reduction in construction costs.

Firstly, the loading coil device 10 prmnits the loading coils to be connected to the lines of a cable within an existing cable pair length connection re-enterable housing. The re-enterable housing is currently required to contain the connections between the cable 10 lines and the fly-leads of the existing (loading coil) canister type device. The necessity of having two housings/canisters at each loading location is thereby avoided if the loading coil device 10 is used.

.oo Secondly, the placement of a plurality of loading coil devices 10 in the normal reenterable housing permits convenient adjustments to individual loading coils on a particular device 10. Any one of the devices 10 that are installed in the housing can also be easily replaced.

Thirdly, a plurality of loading coil devices 10 (and/or the 20 coil variant) can be combined in various ways within the re-enterable housing to make up the desired number of loading coils. Combinations of these two devices therefore can replace the many discrete canister type devices that are currently used in a network.

Figure 7 shows a conventional arrangement for loading cables wherein the load coils are encased in canisters 100 having fly leads 102 which are interconnected with cables 104, by first cutting the cables and then connecting the fly leads 102 to the cut ends at separate encased connections 106. In contrast, Figure 8 shows a loading coil device 10 according to this invention connected to cables 104 simply by connecting the cut ends of the cables to the connector of the loading coil device 10, the entire assembly being contained within a suitable re-enterable housing 120, which may be of conventional type. The arrangement of the assembly of several loading coil devices within the housing 120 is shown in Figure 10. It will be appreciated that, in this case, 940706,p:\AopecmtdcWI1r11pc6 I r -r I _I -7the need to provide the connections 106 and seal them separately as well as separately sealing the load coils in the canisters 100 as in Figure 7 is avoided, and a substantial cost reduction in field work can be obtained.

The re-enterable housing 120 has a base portion 122 to which is securable, such as by a foldover/lever action type clamp or the like, an upper closure member 124.

Cables 104 are passed into the canister by passing these through openings in downwardly depending entry ports 126 and sealing the cables where they pass through these. This sealing may be effected in any suitable fashion such as by the use of heat shrink sleeves 10 with, for example, aluminium foil arranged to provide screen continuity. In the arrangements shown, particularly in Figure 10, the circuit boards are shown mounted on an upwardly extending U-shaped member 128 which may for example, be screwed to the base portion 122 before fitment of the loading coil devices thereto. Then, the cables 104 are attached to the loading coil devices as described and the canister closed by attachment of the closure 124. The loading coil devices 10 are restrained by a zip tie 118, to prevent them moving out of the U-shaped member 128.

i"..-Figures 1 and 6 also show a protection device 20 which is insertable into the .connector 16 to provide for protection against electrical surges produced by lightning strikes or the like. It is in the form of an elongate circuit board having a number of :surge arrestors 22 mounted thereon. Electrical contact paths 130 on the circuit board are shown in Figures 11 and 12. The protection device 20 is pluggable into the connector 16 by sliding it downwardly between the two rows of the posts provided on the connector 16 so that electrical connections are made via contacts 140 on the protection device and connector 16 between individual ones of the surge arrestors 22 and coils 14 and cable pairs. The resultant arrangement is shown in Figure 5 where the surge arrestors are designated F1....F20.

The three electrodes of each surge arrestor 22 are arranged so that when installed in the circuit with the loading coil device 10, one side of a loading coil winding is connected to the first electrode of a surge arrestor 22. The other side of the winding is connected to the centre (second) electrode. The third electrode of the surge arrestor 22 940706,p. opcicm,tcstrI.spc,7 -8is connected to the corresponding winding of a loading coil on the opposite side of the connector 16. This arrangement occurs for each winding of each loading coil and causes significant diversion of electrical surges around the loading coil windings.

The protection device 20 may be installed in the loading coil device 10 where such protection is desirable or not installed where protection is not desirable.

The described construction has been advanced merely by way of explanation, and many modifications and variations may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

0 940706p:\opi~cmlIstrll.spe8

Claims (7)

1. A loading coil device comprising a printed circuit board on which are positioned a plurality of loading coils and an electrical connector, ends of the coils being connected to contacts of the connector via conductive tracks on the printed circuit board, the contacts being of a kind permitting the making of an electrical connection to an insulated wire by pressing the insulated wire between an electrically conductive element such that the insulation of the conductor is cut by at least one edge and electrical contact made between the wire and the at least one edge.

2. A loading coil device according to claim 1 wherein the connector is arranged on the printed circuit board so as to extend lengthwise thereof and the 0'ading coils are arranged to either side of the connector. o 15 3. A loading coil device accorcX ;g to claim 1 or claim 2 wherein the connector is of a o* 9 "kind permitting the insertion thereinto of protection devices. a 9 9

4. A loading coil device according to claim 3 wherein the protection devices incorporate 9 surge arrestors couplable across the coils. A telecommunications system including a plurality of cable pairs for carrying telecommunications signals, which pairs are electrically loaded by a loading coil device comprising a printed circuit board on which are positioned a plurality of loading coils and an electrical connector, ends of the coils being connected to contacts of the connector, via conductive tracks on the printed circuit board, the contacts being a kind permitting the making of an electrical connection to an insulated wire by pressing the insulated wire between an electrically conductive element such that the insulation of the conductor is cut by at least one edge and electrical contact made between the wire and the at least one edge, wherein conductors at adjacent ends of cables of each of the plurality of cable pairs are coupled to a respective loading coil by connection to contacts of said connector. U, 73T H 11 K I U'471 'A (bo 111 N

6. A telecommunications systems according to claim 5 wherein the loading coil device is located in a housing to which the cables enter to be connected to the connector.

7. A telecommunications system as claimed in claim 5 or claim 6 wherein the connector is arranged on the printed circuit board so as to extend lengthwise thereof and the loading coils are arranged to either side of the connector.

8. A telecommunications system as claimed in any one of claims 5 to 7 wherein the connector receives at least one protection device coupling to a respective said coil. A telecommunications system as claimed in claim 8 wherein the protection device is a surge arrestor. A loading coil device substantially as hereinbefore described with reference to the 15 accompanying drawings.

11. A telecommunications system substantially as hereinbefore described with reference to the accompanying drawings. DATED this 13th day of March 1998. TELSTRA CORPORATION LIMITED By its patent attorneys 25 Davies Collison Cave *I I( *1- I I 11 ABSTRACT 10 A loading coil device for interconnecting loading coils to a telephone cable pair. The loading coils are mounted on a circuit board and ends of the coils connected to a screwless terminal device to which the cable pairs may be connected, and which terminal device can receive a surge arrestor device for connection of surge arrestors across the cable pairs. C o o o•* 940728,popcr'cmIcstr L.spc 1