GB301118A - Improvements in or relating to fire alarm systems - Google Patents

Abstract

301,118. Standard Telephones & Cables, Ltd., Searle, A. M., Lowry, L. P., Gould, J. R., and Bates, E. F. Aug. 29, 1927. Fire-alarm systems. - In a system in which substation signals are normally transmitted by 'breaks in a closed loop and in which on a break in the loop the substation is connected to earth only during signalling e.g. as described in Specification 290,743 means is provided at the district station on the occurrence of a break automatically to earth one pole of the battery and connect the other pole in series with the recording means to both line terminals. The Figure shows a substation loop BL1, BL2, operating register Re and gong Go and repeating contacts A2, A3. A break in the loop causes the register Re to actuate relay H so that the release of relay A energizes relay J and de-energizes the normally energized slow to release relay SK so that the operating magnet of switch K is energized. Incoming signals over line BL1 then control relay A which de-energizes relay J and energizes relays D, E, so that the circuit of relay B is broken to prevent interference and the signals are repeated by relay F. The register contact at the end of the call actuates relay H to de-energize relays D, E. Similarly signals on the line BL2 control relay B which de-energizes relay G and energizes relay C which looks .and breaks the circuit of relay D to prevent interference from the line BL and the signals are repeated by relay F. Signals are normally repeated to a central station over a loop L1, L2. In the event of a break in this loop the central station relays de-energize and a lamp La is lighted. The operation of key Ke energizes the actuating magnet of switch P to earth the central station battery and connect it through the register apparatus to the lines in parallel. At the substation relay HR is connected to earth at contact SW3 through contact LB2 and to the lines L1, L2 in parallel and is energized to operate, switch SW through relay SR. Contacts A2, A3 are now earthed and repeat signals from the loop BL1, BL2 over both lines in parallel. If the substation loop is broken the signals are repeated by relay F.. If the line L1, L2 to the central station is repaired relays LC, LD, are operated to energize the re-setting magnet of switch P. At the district station relays LA, LB, are operated to energize the re-setting magnet of switch SW so that the loop L1, L2 is restored to normal.