Improvements in or relating to electrical signalling systems

Abstract

Abstract 534,300. Electric signalling systems. ERICSSON TELEPHONES, Ltd., and DISTIN, L. S. Nov. 9, 1939, No. 29701. [Class 40(i)] In a system for controlling alarm sirens and having means for signalling line faults, the control signals are given by feeding the line with A.C. and connecting one or.other of two halfwave rectifiers in series with it. As shown a signal is given by operating a selecting key KR or KG and then an operating key KS. Operation of KR or KG shunts resistance RE and. rectifier MRR over which Q is normally operated to energize marginal relay S which energizes a pole changer CV, to cause the line to be fed with A.C., and a relay P. Relay A.C. responds when the A.C. reaches a suitable value and cuts off Sand Q, P remaining held by rectified line current and Q by relay A.C. On the operation of KS one of the rectifiers MRG, MRR is inserted in the line and the corresponding relay E, D responds to control the siren. If the line breaks, Q falls back and lights ALI. If it is short-circuited or earthed on the battery side, P pulls up and lights lamp AL2. Audible signals may be provided. Faults may be indicated at the key position, by means of a relay connected in place of resistance RE and normally energized to hold open an alarm circuit.

Inventors

No inventors recorded.

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