Patent GB-431732-A (GB)
Title: Improvements in or relating to electrical systems of remote control and supervision
IPC: H02J13/00
Filed: 1934-03-29
Abstract: 431,732. Electric selective signalling systems. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and SMART, N. C., c/o General Electric Co., Stoke, Coventry. March 29, 1934, No. 9780. [Class 40 (i)] In an electric signalling system in which a number of sub-stations are connected in parallel across a pair of communication channels, a calling substation transmits a signal to the main station over one channel, which signal is the same for all sub-stations and may be transmitted simultaneously by more than one substation, whereupon the main station transmits control currents over the other channel to operate selective devices at all the substations. When a calling substation has been selected a second signal is returned to the main station over the first channel and other calling sub-stations are locked off the signal channels but are retained in a potential signalling condition until transmission from the selected sub-station has terminated. A double check on selection is provided, the main station transmitting first the selecting number and then the complement of a fixed number of impulses, both transmissions being checked back by the selected sub-station. Specification 409,472 is referred to. The equipment at one sub-station is shown in Fig. 2 and that at the main station in Fig. 1. When a circuit breaker or similar device at the substation trips, one of the contacts ZA-ZG opens momentarily and relay CB releases. Relay XS pulls up and closes the circuit over lines 2, 3 to energize relay LC at the main station. The start relay ST (Fig. 1) energizes, relays LS at all sub-stations are operated over lines 4, 5, relay SP falls away and the alarm BE is operated. At all the substations relays B pull up, and at the calling sub-station relay XS falls away and relays YS and ZS pull up. Relay LC (Fig. 1) releases, relay G energizes and relays XC, YC and ZC interact to send impulses over lines 4, 5 to the sub-stations and to step switch SC. At the sub-stations relays LS respond and step switches RS in series with relay C which operates. As the sub-station shown is calling, at the end of the fifth impulse relay XS is energized over wiper RS1 and relay LC (Fig. 1) is re-operated. The relays XS at the substations are connected to different contacts of bank RS1. The operation of LC stops impulsing and relay G releases but relays LS are held over lines 4 and 5. Relay C (Fig. 2) falls away and S energizes causing relays XS, YS and ZS to interact, stepping switch SS and transmitting pulses over lines 2, 3 which are repeated by LC to magnet RC. When wiper SS1 reaches the contact marked by RS2, relay ZS is held and impulsing ceases so that relays LC and CC at the main station fall away. If impulsing has been correctly performed relays SR and OG are now operated in series over wipers RC1 and SC1. Relay SR is individual to the station selected and locks. Relay G is re-energized and the impulse relays XC, YC, ZC again interact stepping switches SC and RS. When wiper SC3 leaves the bank commoning impulsing ceases. At the sub-station, when switch RS is impulsed the circuit of ZS is broken so that impulse transmission again takes place until wipers SS1 and RS2 again complete the circuit of ZS. Relays CB and OK are energized in this circuit, relay CB locking to the contacts ZA-ZG and relay OK switching the line circuits to the supervisory apparatus connected over leads 12. At the main station, if impulsing has been correctly performed, relay DK is operated in series with OG over RC1 and SC1 to stop the alarm BE, light the sub-station indicator lamp SL and switch the line circuits through to supervisory responding apparatus connected over leads 13. Should impulsing have been faulty, either or both relays OK, DK remains unoperated and the alarm BE would not be stopped. At other sub-stations at the end of the first impulse train relays XS and S are not energized so that relays XS, YS and ZS cannot interact. When impulsing ceases LS falls away, B releases and, if the substation is in a calling condition with CB released relay XS is again energized to initiate a transmission cycle. After a successful cycle of supervisory operations, contacts se and ce are opened, by apparatus not shown, relays ST, B, S, SR and DK release, relay SP reoperates and the switches are homed in readiness for another transmission.