GB393327A - Improvements in or relating to electrical signalling systems - Google Patents

Abstract

393,327. Electric signalling systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, TERRONI, T. B. D., 20, Staplands Road, Broadgreen, and TURTON, G. D., 48, Church Road, Stanley, all in Liverpool. Dec. 8, 1931, No. 34053. [Class 40, (i).] In a signalling system employing alternating current of a plurality of different frequencies, the receiver is tuned in turn to the various frequencies and a common responding relay energizes as the circuit is tuned to the various components of the incoming signal and controls the energization of particular relays of a relay group. The tuning of the circuit is effected by a relay chain. When a signal is received over 1, 2, relay X responds and relays A-E energize. When E pulls up it breaks the circuit of A and relays A-E fall away slowly in turn. When A energized the incoming signal was connected to the tuned circuit feeding valve V2 and the tuning of this circuit is altered as each relay of the chain A-E falls away. Assuming the signal contains the third and fourth frequencies of the series, when relay B falls away the tuned circuit responds to the incoming signal and Y operates. Relay C is held energized and relays Z and CC pull up in series, relay CC locking up to x and closing a circuit over, 17. Relay Z shorts out Y and C falls away. The circuit is now tuned to the fourth frequency and Y again energizes, holding D and allowing Z and DD to pull up. DD locks and closes a circuit over 18 and Z releases Y to allow the relay chain to complete its action. The energized relays CC and DD hold up until the received pulse terminates. The valve V3, controlling relay X, may be fed directly from the line circuit and tuning may be effected by a parallel, instead of a series, circuit or by variation of capacity. The relay chain could be replaced by a step-by-step switch.