Patent GB-814118-A (GB)
Title: Circuit arrangement for the storing of calls in automatic telecommunication exchanges
IPC: H04Q3/00
Filed: 1957-04-26
Abstract: 814,118. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. April 26, 1957 [April 28, 1956], No. 13369/57. Class 40 (4). On finding a wanted subscriber busy, a calling subscriber may bring into use a call-storage device which frees the calling line for other calls but maintains a connection between the calling line and the wanted line, blocking the wanted line against further seizure as soon as it becomes free and recalling the calling subscriber (if free), finally completing a call to the wanted subscriber when the calling subscriber answers. The call may be stored on the normal selectors or on additional switches provided for the purpose. First embodiment, Fig. 1; call stored on normal selectors.-Subscriber A, on attempting to call subscriber B in normal fashion via line finder AS and final selector LW and receiving busy tone, stores the call by actuating an earth key ET and hanging up. Relays X, SP and SP1 respond, preventing the operation of release relay AUS and connecting test relay PH to the P-wire of the wanted subscriber B. (If subscriber A subsequently wishes to end the storage of the call, he lifts his receiver to energize relays A and V, depresses his earth key ET to bring up relay X and release relay SP, releases key ET to release relays X and SP1, and replaces his receiver, relays A and V then falling back to energize the release relay AUS.) During call storage the normal busying earth on subscriber A's P-wire is disconnected by the operation of relay SP1 so that subscriber A may receive incoming calls, and he may make other outgoing calls via a selector ASx. When subscriber B becomes free, relay PH is energized, busying B's line and bringing up relays PA and RA to call subscriber A (if he is free). When he replies, the response of relays A and V releases relays SP and SP1, bringing up the normal test relay PB in place of PH. Relay RB operates to call subscriber B and the connection is completed in the normal manner. Second embodiment, Fig. 2; call stored on additional switches.-To store a call, subscriber A dials a code number to set final selector LW1 to the call-storage equipment and then dials the wanted number which is repeated by relay A to set an auxiliary final selector HLW to the line of the wanted subscriber B. The calling subscriber A then hangs up and relays A and V fall back to bring up relay U which enables subscriber A to make another call via ASx. When subscriber B becomes free, provided that subscriber A also is free so that relay V1 is back, test relay P comes up, busying subscriber B, releasing relay U, and energizing relay RA to call subscriber A. On his response the operation of relays A and V1 releases relay RA and brings up relay RB to call subscriber B. If subscriber A had wished to end the storage of the call he would have dialled a predetermined digit, repeated by relay A to set a switch KW to energize the release relay TR. Third embodiment, Fig. 3; preselector system.-Subscriber A seizes storage equipment SP by dialling a particular digit. Relays A and VI operate. Subscriber A then dials the number of the wanted subscriber B which is repeated by relay A, relay V2 holding during each impulse series, so that, with the cooperation of relays U2 and U3, switches HLW, SGW, and SLW are set in turn and one of the group relays GRl-GRx is operated. When subscriber A hangs up, relays A and VI fall back and relay U is energized. Subscriber A may now receive incoming calls, and may initiate calls via an auxiliary preselector HVW. When subscriber B becomes free, relay P1 responds to the potential on the P-wire via selector SLW, busies B's line, completes a circuit for a thermal relay Th, and prepares to connect subscriber A to selector SLW. If subscriber A is free, relay S operates and brings up relay RA to apply ringing current. When subscriber A replies, the response of relays A and V1 operates relay RB to send ringing current to subscriber B. When he answers, relay Y is energized, bringing up relay PH which breaks the circuit for the thermal relay Th and releases relay U1 to switch through the connection. If either of the two subscribers had failed to reply within a predetermined time so that the circuit for relay PH was not completed, the consequent operation of thermal relay Th would have initiated release by means of the release relay TR. If, when subscriber B becomes free, subscriber A is busy; relay S cannot be energized, because of the operation either of relay C, if A is a called subscriber, or of relays A and V1, if subscriber A is calling. After its predetermined delay, thermal relay Th pulls up and operates relay T which disconnects the test circuit and the busying earth from subscriber B's line. When subscriber A becomes free, relay T falls back and re-establishes the test circuit for subscriber B. In a manner not shown, an audible signal is transmitted to sub. scriber A if he is busy when subscriber B becomes free. To end storage of a call, subscriber A operates the release relay TR by dialling a particular digit to set switch SGW to the relevant position.