Patent GB-283252-A (GB)
Title: Improvements in electromechanically controlled telephone systems and switching apparatus therefor
IPC: H04Q3/00
Filed: 1926-09-29
Abstract: 283,252. Baron, H. Sept. 29, 1926, Automatic exchange systems. - In systems using stop-controlled selectors with a number of groups of terminals in a row and controlled directly by incoming impulses, e.g. as described in Specification 254,373, arrangements are made to stop the wipers on any of two or more terminals at the end of each group, and at the end of a digit they are, if necessary, stepped automatically to the last of such terminals in readiness for the next digit or for the hunting operation. Group selector, Fig. 3. The first relapse of line relay 354 energizes dialling relay 362 which shunts resistance 356 to cause relay 357, which has been holding only its dotted armatures, to energize fully. When relay 354 pulls up again, relay 371 pulls up its dotted armatures in series with the control magnet 325 which however remains unoperated. The next impulse thus energizes the control magnet which stops the wipers on 391 or 392 in the middle of the group until the line relay pulls up again, when it is re-energized and subsequently stops them on 398 or 399 at the end of the group. On the relapse of the dialling relay, relay 371 falls back and a circuit is made at 309 for driving the wipers if necessary to the second of the pair of stopping terminals (e.g. 304, 305) and at 310 for driving them off this terminal. Magnet 325 then remains energized over its own contact and wiper 350 until an idle line is reached, whereupon relay 371, which now receives current over its upper winding, pulls up all its armatures to switch the line through. Relay 354 falls back, but the release relay is held over 375, 356. The last of the control terminals of each group, e.g. 320, is left dead to prevent. the wipers from running into the next group. In this case the switching relay does not pull up and busy tone is sent back by means not shown. Connector, Fig. 2. In response to the tens digit, the wipers are moved over groups g1, g2 &c. as in the group selector, and at the end of the digit a change-over relay (not shown) opens contacts 33, 34, 36 and closes 35, 37. If the wipers stopped on the first terminal of the pair b3, b4 &c. magnet M2 now receives an impulse over 60, UB and the wipers move one step to a terminal such as 30 which is the last of a group. The first units impulse energizes magnet M1 of a back-stroke drive auxiliary switch, and at the end of the impulse the switch takes a step and completes a circuit for the magnet M2 of the connector which moves (e.g.) to 41. Subsequent impulses operate both switches in a similar manner. Connector, Fig. 4. Line relay 400 energizes release relay 405 and short circuits the dialling relay 408 which pulls up at the first relapse of relay 400 when the subscriber dials. When relay 400 pulls up again, relay 416 is energized partially by its right-hand winding over 409, 402, 410, 416, 418, 417, 431, wiper 437 and the control magnet 461 (which does not operate) pulls up its dotted armatures, and holds them by its left hand winding in a circuit over off normal contact 462 independently of relay 408. The second relapse of the impulse relay energizes the control magnet over 437, 431, 404, 409 and its next energization over 437, 411, 402, 409. The switch thus makes a series of double hops in the same. way as the group selector, and at the end of the digit the relapse of relay 408 delivers an additional impulse to the control magnet over 415 and a terminal such as 491 to allow the wipers if necessary to move to the next terminals, which are the last of the group. The relapse of relay 408 also energizes over 414, 426, 460, 471, relay 460, which locks up and connects the control magnet to wiper 438 instead of wiper 437. In the case of a first digit 1, the circuit for relay 460 is over 472, 431, 461 instead of 471. When the units digit begins, relay 408 energizes relay 419 sufficiently to attract its dotted armatures. In general, relay 465 at the beginning of each odd impulse pulls up over 495, 438 and the control magnet (which remains de-energized), locks up over 467, 413', and at the end of the impulse remains locked up over its right-hand winding 468, 401. Its lefthand winding however is short-circuited at 401 and the control magnet therefore becomes energized and the wipers are moved one short step, wiper 438 engaging a terminal connected to 501 which is dead. At the beginning of each even impulse, relay 465 falls back and consequently when the impulse relay pulls up again, the control magnet is energized again over 501. If, however, the tens digit was 1, the first units impulse energizes the control magnet direct over 404, 431. Busy test and signal. The relapse of relay 408 connects negative battery over 414, 430 to the upper winding of relay 419, which, if the line is busy remains unalfected, busy tone going back from 481 over 429. Ringing current. If the line is idle, the upper winding of relay 419 is energized over the cut-off relay and the relay pulls up all its armatures, unlocking relay 460 which projects ringing current over the line via common condensers 513, 515. In the silent intervals, a circuit is made via the loop for relay 460 which, when the subscriber replies, cuts off the ringing current and locks itself up. Release. Relay 460 on pulling up for the second time completely energizes relay 416 which locks up so that when the called party hangs up, relay 405 is short-circuited over 456, 442, 422, 409 and releases relay 419 and energizes the control magnet. Premature release. If the call is abandoned after a single tens impulse has been sent, the relapse of relay 403 energizes the control magnet (relay 416 being held over 462 even after the relapse of relay 408) to move the switch off normal and on the relapse of relay 405 the magnet is energized over the off-normal contact 464. If the call is abandoned before any tens impulses have been sent the control magnet is not energized at all.