GB599884A - Improvements relating to automatic telephone and like selective signalling systems - Google Patents

Abstract

599,884. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and VOSPER, W. T. Sept. 28, 1945, No. 25281. [Class 40 (iv)] An impulse correcting circuit contains a ! " watching " relay having respective release and operating lags equal to the required minimum durations of the make-and-break portions of the impulse and intervenes, if necessary, to ensure that an impulse repeating relay produces impulses having at least the minimum make-and-break periods. In the embodiment shown the impulses received by relay A are retransmitted by the high speed impulse repeating relay IR under control of the watching relay IC whose coils are wound differentially so that the charging current of condenser QA delays the operation of the relay and discharge of QA through its coils in series delays its release. Rectifier MRA confines the condenser discharge to the coils of IC. The respective operate and release lags of relay IC are made equal to the required minimum make- and-break periods. When A makes initially IR and IC follow, the former locking up both. When A first releases TR is short-circuited and releases but IC holds on account of its release lag. When A reoperates IR cannot reoperate until IC has fallen back and closed its operating circuit at ic1, the operating circuit for IC being closed simultaneously with that of IR. On the next release of A, relay IR cannot be released until IC has operated to complete the short circuit at ic2.