Patent GB-677230-A (GB)
Title: Remote control system, signal transmission or telecommunication systems
IPC: H04Q9/04
Filed: 1948-05-03
Abstract: 677,230. Electric selective signalling. HEWITTIC SOC. ANON. May 3, 1948. [May 2, 1947] No. 12128/48. Class 40 (i). In a remote control system, synchronous distributers at the controlling and controlled stations are stepped by local timing circuits simultaneously from a starting position and the signalling impulses which may vary in polarity according to the control or indication being transmitted are used to vary the timing of one of the local timers to effect synchronism. At the controlled station II the change of state of, e.g. a circuit breaker D1, mechanically throws a two-way switch 61 associated with a corresponding contact in the distributer bank 24 and, as disclosed in Specification 620,710, causes a two-way switch 26 to be actuated from the position shown to energize the starting relays 52, 22 at the controlling and controlled stations I, II from battery 25 over the transmission lines 1, 2, and the wipers of the distributer banks 54, 24 in their normal positions. The starting relays at their contacts 51, 21 remove short-circuits from respective timing relays 35, 5 and further relays 45, 15 whereupon the timing relays, lagged by the shunting condensers 36, 6 self-interrupt and over closed contacts of the energized relays 45, 15 interact with the respective stepping magnets 43, 13 to advance the associated distributers at the stations I, II, synchronously. In the offnormal positions of the distributer 24 positive or negative is connected over the distributer arm and a contact 7 of the timing relay 5 to line 1 dependent on the state "on" or "off" of the associated circuit-breaker D1 and hence its mechanically actuated switch 61. At the station I a two-pole two-way control switch 67 is connected to each contact of the distributer 54 corresponding to the associated circuit breaker at station II. If the position of a switch 67 agrees with that of the switch 61 of the asociated circuit-breaker D1 then as the distributers 54, 24 sweep the corresponding bank contacts, e.g. 60, 66, a relay 74 is energized at station I. If the switch positions do not agree, however, relays 75, 76 are energized in series. Relay 76 energizes the lamp 68 over the distributer bank 80 to indicate the disagreement, the lamp flickering, i.e. being lit periodically once during each rotation of the distributers. A push-button 69 corresponding to the circuitbreaker in question is now depressed so that when the wiper reaches the associated contact 85 the high resistance relay 76 is short-circuited, whereupon the appropriate preparatory relay 62 (or 63) at station II energizes in series with 75 and effects, as in Specification 623,214, change over of the circuit-breaker D1. At each position of the distributers the energization of relay 74 or relays 75, 76 short circuits a resistance 59 in the timing circuit of relay 35 so that the release time thereof is synchronised with that of timing relay 5 at station II. Hence the distributers are stepped synchronously only if a signal is transmitted at each step. Should the transmission line be broken or no signal transmitted the timing relays 35, 5 function independently to step the distributers 54, ... , 24, ... to normal. Modifications. The two relays 75, 76 may be replaced by a gas tube or vacuum tube relay, Fig. 2 (not shown), and an arrangement is described, Fig. 3 (not shown), for preventing a signal effecting its desired operation in the event of parasitic potentials appearing on the distributer contacts immediately before and following the signalling contact.