GB418306A - Improvements relating to electric signalling systems - Google Patents

Abstract

418,306. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and HUMPHRIES, H. E., 61, Rochester Way, Blackheath, both in London. April 19, 1933, No. 11418. [Class 40 (iv).] In an electric signalling system comprising a pair of signal receiving relays P, PA connected to a signalling wire, the operation of one or other of the relays being dependent on the direction of current flow, a potential always applied at a certain stage in the signalling operations is adapted to operate one of the relays (P), but a prior application of potential or potentials prevents the operation of this relay and determines whether the other relay (PA) shall operate. The signalling may be between two points connected by a hunting switch and the potential for operating PA is applied when the receiving point is picked up but is removed subsequent to a switching operation completing the connection between the two points. The arrangement shown comprises two selecting stages S1, S2, the switches of which are driven by electromotors normally locked by electromagnetic latches and controlled by common marker circuits CC1, CC2. S1 is regarded as the transmitting point and S2 the receiving point. At S1, contacts e, f of relays (not shown) may be both open, both closed, or either closed, according to the route to be take at a subsequent stage, or to the class of calling subscriber (for signalling an operator), while at S2, the two signal receiving relays P, PA are connected to the positive wire over oppositely poled rectifiers r1, r2. The contacts k of the coupling relay (not shown) at S1 are closed and assuming f closed and e open, booster battery AB is connected to the positive wire when latch magnet contacts lm close on termination of the hunting movement of S1. Signal relay PA therefore operates and may, if desired, lock up. Shortly afterwards, S1 switches through at 1h and signal relay P is operated over the calling loop in series with 2A. P may also lock up, but as shown is released by b. Relay PA should be made quick to operate or the contacts 1h of the switching relay should be sufficiently slow to allow PA to operate. PA is also provided with a slug to absorb the back kick when it de-energizes as this might operate P. If contacts e are closed, P is short-circuited when the switch through occurs and remains inert. The negative and any other wire may be used for similar or other signalling purposes. According to the Provisional Specification, the relays P, PA may be polarized.