Patent GB-143108-A (GB)
Abstract: 143,108. Western Electric Co., and Deakin, G. Aug. 19, 1919. Automatic exchange systems.-When a subscriber calls a number not corresponding to an exchange line, the switches taken into use are at once released and made available for further calls. The invention is described with reference to an automatic private branch exchange of 200 lines, the switches being released when the first digit called is any number but 1 or 2. A subscriber who desires a connexion to the main exchange, calls the single digit O, which sets a register in a position in which, in addition to releasing the switches, it closes a circuit for lighting a lamp individual to the calling subscriber at an auxiliary manual switchboard, where an operator connects him to the main exchange. All the calls from any particular subscriber can be diverted direct to the manual switchboard by throwing a key at this switchboard. Incoming calls from the main exchange are dealt with manually by the local operator, who is able to break in on existing automatic connexions. Fig. 1 shows the circuits of two P.B.X. subscribers 100, 150 and the manual switchboard arrangements for interconnecting them or for making connexion with an exchange line 190. Local connexions are normally made by a call-finder and connector circuit, shown in Fig. 2, which is connected by a hunting-switch, shown at the foot of Fig. 2, to an idle register-controller, Fig. 3. The 200 lines in the connector terminal bank are arranged in ten levels of twenty, subscribers whose hundreds digit is 2 being connected to the first half of the bank, and those whose hundreds digit is 1 to the second half. Although the subscribers are designated by 3-digit numbers, only two registers 320, 330, Fig. 3, are provided, the hundreds digit being accounted for by a pair of relays 367, 368 which are energized or not according as this digit is 1 or 2; if these relays are energized, the connector brushes are rotated an extra ten steps. The registers move always in one direction, from position 0 round to position 0 again, and the subscriber's impulse senders are therefore designed on a complementary basis, so that if the wanted subscriber's tens digit is 3, seven impulses will be sent and the tens register will be set to position 7. Call-finder. A calling-subscriber's line relay 110 energizes a pilot relay 118 which energizes relay 239 of each accessible call-finder to energize its power magnet 250. When a finder arrives at the calling line, the right-hand winding of relay 263 is energized over brush 238, and this relay locks itself over its low-resistance left-hand winding in series with relay 265, which open-circuits the power magnet 250 and drives sequence-switch 200 to its 4th position, de-energizing relays 239, 263, 265 and closing a circuit for relays 112, 114, and 242 through brush 237. Relays 112 and 242 are energized, but the current is insufficient to energize relay 114. Relay 112 de-energizes relays 110 and 118 so as to stop the other callfinders, and relay 242 energizes relay 252 over the calling line. (If two finders should have stopped simultaneously on the calling line, the divided current through t.he low-resistance holding-circuits of relays 263, 265 will be insufficient to energize these relays. In this case, as each switch 200 passes through its second position, circuits are closed through the release relays 258, which lock up and restore the circuits to normal. Relays 258 also keep open the circuit through brush 237, so that the calling line can be seized by the next finder that reaches it.) Selection of idle register-controller. In the 4th position of switch 200, the hunting switch 290 is energized in a circuit 230, 298, and searches for an idle register-controller as described in Specification 4489/14. When it reaches the idle register-controller shown in Fig. 3, the right-hand winding of relay 263 is energized in a circuit 298, 222, 299, 305 in series with relay 354. Relay 263 locks up over its low-resistance left-hand winding in series with relay 265, which stops the switch 290 and drives switch 200 to its 5th position, in which contacts 201, 202 transfer the calling line from relay 252 to stepping-relay 352. Relay 354 closes a circuit over its left-hand winding to drive switch 300 to its 3rd position, and relapses as soon as the switch passes out of its 2nd position, its circuit being opened at contact 305. Relays 263, 265 remain energized in the circuit 299, 305, 306. (If two hunting-switches connect simultaneously to the same register-controller, the divided current from circuit 299 is insufficient to energize the relays 263, 265, so that the switches move forward again to find another register-controller.) Setting of the registers. With the switch 300 in its 3rd position, the energization of stepping- relay 352 closes a circuit over contact 307 through the left-hand winding of relay 361 and also through its right-hand winding and in parallel through relay 362 and register magnet 320. Relay 361, being differentially wound, does not respond, but relay 362 becomes energized and grounds the above circuit independently of relay 352, and magnet 320 moves the register out of its zero position, grounding contact 321, which short-circuits the right-hand winding of relay 361 so that this relay now becomes energized. The register 320 therefore stops in its 1st position, in which contact 321 is opened again. In the meantime, a tone signal is sent back to the calling subscriber by an interruptetr 350, as a notification that he may begin sending impulses. The de-energization of relay 352, in response to the first impulse, unlocks relay 361, and the re-energization of relay 352 at the termination of the impulse causes the register 320 to move forward a step, as described above; in the same way the register takes another step at the termination of each succeeding impulse. The last impulse of the series is prolonged sufficiently to energize a slow-response relay 353, which energizes relay 354, which drives switch 300 to its 7th position. Since the called subscriber's hundreds digit is either 1 or 2, the register 320 will have been driven to either its 8th or its 9th position; in the latter case, as switch 300 runs through its 4th position, contact 304 closes a circuit through register contact 324 to energize relays 367, 368, which lock themselves up, but if the register 320 is in its 8th position, these relays will not be energized. As the switch 300 runs through its 5th position, it closes a circuit 310, 326, 322 for driving the register 320 from its 8th or 9th position to zero. (If the subscriber sends any figure from 3 to 9 for the first digit, the release of the entire connexion is initiated by a circuit closed through contact 327 and relay 371, and the operations begin afresh, the subscriber getting a tone signal again as soon as he is connected to another register-set as a notification that he should repeat his impulses.) In the 7th position of switch 300, relay 352 sets the register 320 to a position determined by the tens impulses. Relay 353 then drives the switch 300 to its 10th position, in which the register 330 is set by the units impulses, and the switch 300 is driven to its 12th position. The locking circuit of relays 367, 368 is now transferred from contact 311 to contacts 335, 304. Connector. With the switches 200, 300 in their 5th and 12th positions, a fundamental circuit 294 is closed through relays 239, 373. Relay 239 drives switch 200 to its 6th position, energizing the magnet 260, which rotates the brush-tripping spindle. As this spindle rotates, the interrupter 245 intermittingly connects ground through contact 203 to the fundamental circuit, so as intermittingly to short-circuit relay 373. This relay and relays 372, 374 control the register 320 in just the same way as relays 352, 362, 361, already described, advancing it in step with the brushchoosing spindle. When the register reaches its zero position, the next de-energization of relay 373 completes a circuit 314, 313, 323, 317, and in parallel through switch 300 and relay 371. The switch 300 moves to its 14th position, open-circuiting relay 371 at contact 317, but in the meantime this relay has opened the fundamental circuit, de-energizing relay 239, which open-circuits magnet 260 and drives switch 200 to its 7th position, from which it is driven on at once to its 8th position, the relay 239 having become energized again in the fundamental circuit. The magnet 240 is now energized and rotates the brush-carriage to trip the selected sets of brushes and to move them to the terminals of the wanted subscriber. This movement is controlled by the units register 330 (which is moved step by step under control of relay 373) in conjunction with the relays 367, 368. If these relays are un-energized, relay 371 and switch 300 are energized over the circuit 314, 313, 333, 334, 317 at the first deenergization of relay 373 after the register has returned to zero; but if the relays 367, 368 are energized, this circuit is open at the back contact of relay 368, and the register 330 makes another complete cycle, corresponding to a movement of the connector brushes over 10 additional sets of terminals. As the register on its second cycle passes from its zero to its 1st position, the locking-circuit of relays 367, 368 is opened at contact 335, so that when the register again arrives at zero, relay 371 and switch 300 are energized, Switch 300 moves to its 16th position, in which circuits are closed for advancing it to its 17th and again to its normal 1st position. Relay 371 opens the fundamental circuit, de-energizing relay 239, which open-circuits magnet 240 and drives switch 200 to its 11th position, disengaging the restored register-controller by opening circuits 299 &c. Busy test. As switch 200 passes through its 10th position, relay 263 (which was just previously unlocked by the op