Patent GB-296304-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/42
Filed: 1928-08-22
Abstract: 296,304. Associated Telephone & Telegraph Co., (Assignees of Stehlik, R. F.). Aug. 37, 1927, [Convention date]. Automatic and semi-automatic exchange systems. - In a call from an automatic to a manual exchange, a repeater R, Fig. 1, is selectable by an office selector OS only if it has been pre-selected by a register-controller. Figs. 4, 5; a secondary switch SS is set in action to find a junction TL only when all the digits have been registered; a junction TL is selectable by the switch SS only if at its incoming end it has been pre-selected by one of the registering-sets RG1, RG2, Fig. 6; the wanted number is transmitted between the exchanges, two digits at a time, the sender being adapted to act on a loop circuit with the same effect as if it were two separate leg impulsing circuits. Specification 216,087 is referred to. Pre-selection of repeater R by register-controller. Ground on the wiper 420 of a common switch D energizes relay 422 and de-energizes 421 to close a circuit for magnet 423, which advances the switch until wiper 420 reaches an ungrounded terminal. Relay 422 then falls back and 421 is energized and grounds wiper 419 to close a circuit for magnet 120 in series with relay 401. Relay 421 also bridges wipers 417, 418 to connect magnet 120 to wiper 121. The switch F therefore advances until this wiper reaches an ungrounded terminal. Relay 401, previously shortcircuited, is then energized and grounds wiper 121 from 419 to energize relay 114, which locks itself, returns ground over 121 to hold 401, and removes ground from wire 108 to render the repeater R selectable to office selectors OS. Relay 4U1 also grounds the wiper 420 to start the switch D on its job of associating another idle register-controller with another idle repeater. Marking junctions busy unless associated with a register-set at the incoming end. Normally the guard-wire 208 of a junction is grounded over back contacts of relays 210 - - 212. When a register-set RG1 is associated with the junction its incoming end is connected to relays 610, 611, and the. high-resistance relay 212 is energized to unground the wire 208. Register-controller; secondary switch SS. The dialled digits (subsequent to the first, which operates the office selector OS) are repeated by relay 111 over 124 to the registers TH, H, T, U, Fig. 5, the switch SE being stepped after each digit, and ground is then connected by the lower wiper of SE over 123 to relay 201, which locks to wire 118 and starts the switch SS to find a junction TL. Ground is then fed forward over wire 208 to emergize relay 210 which disconneets. relay 212. Re-transmission of digits. Relays 610, 611 at the manual exchange are now connected over the junction in loop with a high-resistance relay 405, which energizes 406, which locks itself and extends the loop over wires 416, 415. Wire 413 is grounded so that magnet 504 is intermittently energized under control of relay 505 to drive the sender S. After the first step the wire 510 is grounded so that each subsequent relapse of 505 energizes relays 506, 508 (the marginal series relays 507, 509 are not energized). In order that two digits may be sent simultaneously, the relays 506, 508 control the loop 416, 415 in such a manner that each energization of relay 506 deenergizes relay 611 and each energization of 508 de-energizes 610 : when both relays 506, 508 are energized the loop is opened, but when only one of them is energized (as will occur when one digit is longer than the other) one side of the loop is opened and the other side is kept closed. As soon as the required thousands digit has been sent, relay 507 is energized over 502 to disconnect 506, and as soon as the tens digit has been sent, relay 509 is energized over 503 to disconnect 508. As the sender passes its mid-position ground is taken off the wire 510 to unlock 507, 509, and during the second half of its movement the hundreds and units digits are transmitted in the same way. Release of register-controller. Ground is then connected to wire 412 to energize Delay 402, which connects wires 413, 412 so that the sender takes only one more step to its normal position. Relay 402 releases relay 406 and also unlocks 401 which grounds wire 411 to restore the switch SE and the registers. The registerccntroller is now again selectable, its terminal in the bank of wiper 420 being no longer grounded. Ground momentarily applied by relay 402 to wiper 124 energizes relay 115, which locks up and switches through. Registers and lamp indicator at manual exchange. Relays 610, 611 are connected to the junction loop by relay 608 and energize relay 612. The thousands and hundreds digits are repeated by 611 to registers TH, H and simultaneously the tens and units digits are repeated by 610 to T, U. The display relay 613 is then energized (provided the corresponding relay 613' of the second register-set RG2 is inert) to light the indicator CLB and to energize relay 305 which lights lamp 308 in the junction cord CC. Busy test and tone. The operator tests the wanted line over circuit OTC, and if it is busy presses a common key 310 to energize relay 301, which is locked by 302, and busy tone is sent back from BT. Supply of ringing current. If the line is idle the operator plugs in, energizing relay 307 which opens the busy-tone circuit, closes a ringing circuit RI, and energizes 301, 302. Ringing tone is sent back over the upper right winding of the feed repeater. On the subscriber's reply, relay 306 is energized, removes a short-circuit from its upper winding, and completes the talking circuit. Relay 304 is energized, removes a short-circuit from its upper winding, and energizes the reversing relay 303, and the reversal is repeated to the calling line by relay 110. Release of registers and indicator. The energization of relay 301, as soon as the operator attends to the call, de-energizes relays 610, 611, 612 to close a release circuit for the registers and grounds wire 323, short-circuiting relay 608 and closing a circuit for magnet 607 to advance the switch FR1 to the next idle junction cord. A relay 609 in the release circuit delays the hunt until the release of the registers is completed. Relay 609 is also energized if all cords are busy, its upper winding being then no longer shortcircuited over wire 326. Circuits over the wipers 605, 606 prevent the switch F'Rl from seizing a cord occupied by FR2, the stepping magnet of the hunting switch being operated directly from earth on the wiper of the other switch. Release of connection. When the calling subscriber hangs up, relays 111, 112 relapse and 113 is momentarily energized to take ground off the wire 108 to release the switches LS, OS. Removal of ground from wire 118 de-energizes relays 115, 201, 202, 210, and relay 212 is again energized over the junction to keep 211 locked. Relay 302 is de-energized (212 being highresistance) and lights lamp 309, and the operator takes down the plug. Relays 306, 307, 301 fall back, and the opening of the junction de-energizes 212, which unlocks 211 but keeps the wire 208 grounded until a register-set is again connected to the junction at its manual end.