. Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems . stening key in her cordcircuit, and after ascertaining the rural-line party desired by the auto-matic subscriber used, inserts the toll plug in the jack of the proper ruralline, circuit of which is similar to that shown in Fig. 242, and sends outthe proper signal. The supervisory features have already been the calling automatic subscriber disconnects before the operatorwithdraws her plug from the trunk jack, the cut-off relay closes circuitfrom earth through the back contact of the slow-act
. Automatic telephony; a comprehensive treatise on automatic and semi-automatic systems . stening key in her cordcircuit, and after ascertaining the rural-line party desired by the auto-matic subscriber used, inserts the toll plug in the jack of the proper ruralline, circuit of which is similar to that shown in Fig. 242, and sends outthe proper signal. The supervisory features have already been the calling automatic subscriber disconnects before the operatorwithdraws her plug from the trunk jack, the cut-off relay closes circuitfrom earth through the back contact of the slow-acting relay B, to therelease trunk so soon as the armature of B falls back. Since the circuitthrough B is not broken, however, until the armature of the slow-actingrelay A falls back, B does not complete the circuit to the release trunkuntil the selector switches have had time to release The purpose ofconnecting the release trunk to earth after the switches have released, isto prevent the trunk being seized by another subscriber before the op-erator has withdrawn the plug from the Dist Frame ,§ ■■Through of her Vjsuals to Ground Res. Coil Fig. 245.—An overflow trunk from a toll switchboard to an automatic switchboard. Since the circuits, of chief operators and monitors desks, throughswitching toll cord circuits, toll test panels, etc., may be the same as anyefficient circuits used in manual practice, space will not be occupied bya description of them. Overflow Trunks.—One end of an overflow trunk is shown in The other end terminates in selectors and reversing battery con-nectors, the circuits of which have been explained in a previous the automatic plug of the toll cord circuit is inserted in the jack ofan overflow trunk, the third strand of the cord is connected to negativebattery, through the 1300-ohm busy-control relay of the trunk. RelayA of the cord circuit therefore does not operate but the busy-control relayof the trunk does so, closes
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttelephone, bookyear19
