Patent GB-763564-A (GB)
Title: Improvements in telephone systems
IPC: H04Q3/00
Filed: 1954-12-01
Abstract: 763,564. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Dec. 1, 1954 [Dec. 3, 1953], No. 34799/54. Class 40 (4). A plurality of subscribers' lines are connected to a satellite switching centre which is connected by a plurality of junctions and control conductors to an exchange containing a register, the satellite including a translator operable under the control of the register and a busy-test connection for each line which may be extended, under control of the translator, over one of the control conductors to a busy-test device at the exchange ; when a wanted line is found idle, control potentials are applied to a control conductor and a conductor of one of the junctions in order to operate a switching means controlled by a gas-filled discharge tube, thereby connecting the wanted line to the exchange over the said one of the junctions. In the drawings, which should be arranged as shown in Fig. 10, the satellite is shown in Figs. 1 and 3 and the exchange in Fig. 2 and Figs. 4-9. The equipment shown is intended for use with a cross-bar exchange of the type described in U.S.A. Specification 2,585,904, in which the subscribers' lines are identified according to their locations on a line link frame, each frame having a maximum of six hundred lines arranged in ten horizontal groups or levels and a maximum of twelve vertical groups, each vertical group including five vertical files. The lines appearing in each horizontal group are served by ten line links which connect the primary line switches with each of ten secondary or line junctor switches. A wanted line is identified to the marker which controls the operation of the cross-bar switches by means of a two-digit frame designation, a vertical group digit, a horizontal group digit, and a vertical file digit. In the present system a maximum of twelve satellites are provided, identified by the vertical group digit. Each satellite serves a maximum of fifty subscribers' lines, identified by a combination of the hori. zontal group digit and the vertical file digit, and is connected to the exchange by twelve junctions. These appear in the ten-line junctor switches of the line link frame, four of the junctions being arranged in two pairs for this purpose. Between the satellite and the exchange there are also four control conductors 100-103. Scanning pulses are sent over conductors 102 and 103 by a generator 402, Fig. 4, and are directed by a known type of line scanner 104, 105, Fig. 1, to each subscriber's line in turn, so that each line corresponds to a particular time position in a recurring cycle of such positions. Call initiated at satellite substation 110 corresponding to time position " 00." A shunt is completed through the calling substation round resistance 109 in the line scanner, so that a stronger scanning pulse is produced in the corresponding time position " 00." This is amplified at 403 in the exchange and detected by tube 404, Fig. 4, its effect being sufficiently lengthened by condenser 435 to cause the operation of relay VGS individual to the relevant satellite. Battery is thereby placed on leads 405 and 406, causing the line link marker connector 407 to select an idle marker 408 and connect it to the line link frame on which the calling satellite appears. Earth on lead 409 identifies to the marker the vertical group in the frame to which the satellite corresponds, and the marker operates the relevant vertical group relay VGAO. This completes a holding circuit for VGS over tube 404, and switches the output of the amplifier 403 from tube 404 to conductor 410 which leads to a common line link frame scanner 700, Fig. 7, which is similar to the line scanner at the satellite. The scanner 700 applies a signal to each of fifty gates, such as 703 or 704, in turn. In the time position " 00 " of the calling line this coincides with a signal on conductor 410, so that the corresponding gate 704 is enabled and passes a positive pulse to lead 705 and thence through the tens and units translator to the relevant tens lead 710 and units lead 720. In an array of flip-flops, Fig. 9, tubes 900 and 902 now fire, extinguishing the other halves 901 and 903 of their flip-flops and bringing up associated register relays TO (in the tens register, Fig. 6) and UO (in the units register, Fig. 8). A control tube 908 also fires, causing conductor 911 to become negative with respect to the grid bias resistors of the flip-flop tubes so that no further tubes can be fired. The register relays connect conductor 510 (connected to battery as described below) to leads 500-507 in a three-out-of-eight marking code. In the present example leads 505, 506, and 507 are so connected. The register relays also selectively mark leads 610-614 and 820-829, indicating to the marker 408 the tens (vertical file) and units (horizontal group) digits. Meanwhile the marker operates the line link frame connector 416, followed by relay VGBO which extends line link test leads 420-429 from connector 416 to the sleeve conductors of the junctions Nos. 0-11 leading to the satellite. Preliminary busy test of paired junctions. Junctions Nos. 8 and 9 are paired and both appear in line junctor switch LJ8, while Nos. 10 and 11 appear in LJ9. Each pair is provided with a preference circuit. Thus relays DTA and DTB are connected to the sleeve conductors 220 and 221 of junctions Nos. 10 and 11 respectively. The operation of vertical group relay VGAO connects battery to relays DTA and DTB, and if either junction is busy the corresponding relay operates and locks. If No. 10 is busy, DTA holds open the circuit of relay PB and the busy test lead 417 remains connected to the sleeve conductor 220 of the busy junction so that the marker cannot select the second junction of the pair, even if it is idle. If No. 11 is busy, DTB and VGBO complete a circuit for relay PB which connects the test lead 417 to the busy junction. Connection of exchange to calling line. The operation of relay VGBO completes a circuit to check that one and only one register relay is operated in each of the registers. This circuit extends from battery through the winding of relay SCC, Fig. 5, and thence over conductor 434 and contacts of the T and U register relays to earth. Relay SCC operates, bringing up relay TA at the satellite and relays TA, Fig. 4, and NGP, Fig. 5, at the exchange in a circuit over control conductor 101. The TA relays disconnect control conductors 102 and 103 from the line scanner 104, 105 and the common scanner 700, and NGP energizes relays CCP, LTS1, and LTS2, Fig. 5, at the exchange and NGC0 and NGC1 at the satellite. The tip conductors, such as 440, of junctions Nos. 0-7, are now connected at the satellite to the relays of the translator, Fig. 3, and at the exchange to the leads 500-507 which are marked, by means of the register relays as previously described, in a three-out-of-eight code with battery now applied to conductor 510 by relay LTS2. Thus the relevant translator relays, in the present example 305, 306 and 307, are operated, extending the battery to control conductor 101 in order to release relay NGP, which connects holding battery to conductor 101 and releases LTS1, LTS2, NGC0, and NGC1, restoring the junctions to normal. The translator relays complete a line test circuit which extends from negative battery at the exchange over control conductor 100, a resistance 113 associated with the calling line, and control conductor 103 to the grid of tube LBT, Fig. 5. The calling line 110 being idle, the potential applied to the grid of tube LBT is not such as to fire the tube and the busy relay LB remains unoperated. As described in the above - mentioned U.S.A. Specification 2,585,904, the marker 408 selects an idle channel including, say, junction No. 0 and connects battery to one of the leads 550-559, in this example 550, to operate relay TSO (one of ten, TS0-TS9), Fig. 5. This in turn operates the corresponding select magnet 230 in series with lamp L0 and also extends sleeve conductor 210 and tip conductor 440 of the selected junction No. 0 to contacts of relay LH, Fig. 5. The marker connects earth to lead 470, operating relay LH which extends negative battery over control conductor 103 and through the translator to the cathode of tube 116 individual to the calling line 110 and also extends positive battery over the right-hand winding of relay CC, tip conductor 440, and the windings of the crosspoint relays 130, 131, &c. associated with the selected junction to the corresponding anodes of line tubes 116, 117, &c. Tube 116 breaks down, permitting the operation of cross-point relay 130 which connects the calling line 110 to junction No. 0 and locks in a shunt circuit round tube 116, which is thereby extinguished. The lockout protection is of the well-known type shown, for example, in Specification 665,519. Relay CC, Fig. 5, operates in series with 130 and initiates release of the marker 408 and the rest of the control equipment. Completion of connection to wanted line. The calling subscriber 110 dials the wanted number, which is registered and then transferred to a marker (408 or another similar) together with the identities of the calling line and the junction used, which have been registered previously. The marker operates the relevant line link frame connector 416 and relay VGB0 to select the control equipment associated with the calling line. The marker also connects negative battery to horizontal group lead 480 (one of ten) and vertical file lead 470 (one of five). The corresponding units and tens flipflops, Fig. 9, respond and initiate the setting up of a line test circuit as before. This time the calling line 110 is found to be connected over junction No. 0 to a register at the exchange so that the potential applied to the grid of tube LBT is such as to cause the tube to fire, energizing busy relay LB. This opens the operating circuit of relay LH and gives a busy indication to