Patent GB-261104-A (GB)
Title: Improvements in automatic and semi-automatic telephony
IPC: H04Q3/42
Filed: 1925-08-14
Abstract: 261,104. Standard Telephones & Cables, Ltd., (formerly Western Electric Co., Ltd.), Moir, R. A., and Hartley, G. C. Aug. 14, 1925. Semi-automatic exchange systems. - The storage relays of a coder are partially energized in groups over a fourth wiper of the code-sending switch PS which, during reception, acts as a digit distributor, to prepare themselves for complete operation in accordance with the setting of the receiving switch PR. In the arrangement shown in Figs. 1 (20470/25) and 2 (20470/25) the switch PR is restored after each digit on the relapse of a sluggish relay SC which is disconnected by the series relay SP when the latter connects the marking ground to the storage relays. In a modification, Fig. 1 (5201/26), the relay SC is made quick acting but is provided with an additional winding 3, 4 which is included in the marking circuit. This circuit is broken as soon as the storage relays are fully energized and relay SC then completes the restoring circuit for switch PR immediately. This arrangement minimizes the risk of a digit being received before the receiving switch is ready for it. Receiving, storing, transmitting and normal release. When the coder is seized, ground on RT energizes relay LD which energizes relay SM and grounds wiper 4 of switch PS whereupon the compensating digit relays HC, LC pull up their fly contacts 5. Ground impulses over PT from the register-controller pass over relay SP to the magnet DM1 of receiving switch PR. At the first step relay SC pulls up and energizes magnet DM2 of the reversedrive switch PS. At the end of each digit relay SP disconnects relay SC and connects PR(1) over PR(2 - - 4) to the storage relays which pull up all their armatures and lock up breaking the circuit over PR(1 - - 4). When relay SC falls back a restoring circuit is made for switch PR and switch PS takes a step whereupon the unoperated storage relays of the preceding group release their fly contacts and all the relays of the new group pull up theirs. When all the digits have been received, PS(4) in position 6 energizes relay US which locks itself, disconnects one winding of relay LD but short-circuits the other to delay its relapse. If a call indicator is not ready, battery and ground on MN, MP energize relay LS which makes a new circuit for relay LD. When the call indicator is ready, relay LS releases relay LD which completes a circuit for magnet DM2 over the machine driven springs MS. The switch PS then moves on and sends the code over MN, MP. At the end of the code, switch PS is in its fifth position and wiper 1 from which the driving magnet derives its ground is connected to ground through relay CO instead of direct. Relay CO pulls up in two steps, armature 26 coming up first, completes a selfinterrupting circuit for magnet DM2, cuts off the storage relays and relay US, grounds PT to cause the relay group to switch through and release the coder and grounds the release trunk RT to mark the coder busy until the switch PS has returned. When the switch PS reaches normal, relay CO falls back. Premature release, faulty operation and alarm signals. If relay LD is released before registration is complete, relay CO pulls up partially in a circuit C027, LD8, US9, CO12, PS1, and then fully releases the coder. If relay CO is operated for a prolonged period, an alarm is operated over SS. If the switch PR fails to restore after a digit other than the last, relay SA is energized long enough to release relay SM, whereupon relay PA pulls up over SA12, SM6, LD13, locks itself, gives an alarm and causes the coder to be released and marked busy and the subscriber to be switched through as described in Specification 258,962. If, however, switch PR sticks after the last digit, the correct code is sent since relay SM is held by relay LS until after the relapse of relay LD, but, when relay CO falls back on the restoration of switch PS, relay LD pulls up over US34, CO28 to SA14 and relay PA gives an alarm as before. If switch PS fails to move when put under control of the interrupter MS by the relapse of relay LD, the relapse of relay SM completes a circuit US28, PS4, SA12 for relay PA.