Patent GB-590372-A (GB)
Title: Improvements in or relating to electric signalling systems
IPC: H04M19/02
Filed: 1944-07-26
Abstract: 590,372. Electric selective signalling. STANDARD TELEPHONES & CABLES, Ltd., McWHIRTER, E. M. S., FONSECA, H. M. M. D'ASSIS-, and WARD, H. J. July 26, 1944, No. 14300. [Class 40 (i)] In a system of signalling by impulse trains, each train has a constant number of impulses divided into variable digits distinguished by alternately reversing the polarity of the digits. In the embodiment described, the selection code comprises thirteen impulses divided into three groups by which an operator at a control station may select a particular piece of apparatus, e.g. a circuitbreaker and control it as by closing or tripping. Control equipment. Operation of a selection key PK, Fig. 1, corresponding to the apparatus to be controlled, energizes relay PD and so allows switch PS to self-drive to the contact marked in PS1 by the key. Relay PH then operates, lighting an indicator lamp PL, after which the key may be released. The operator actuates key CK or TK according to whether the circuit-breaker is to be closed or tripped, thus energizing, relays TL and CR or TL alone. Relay CST operates and locks and connects an impulse generator IG in series with relay CSA which delivers stepping impulses to switch CS. In positions 1 to 3 of switch CS, relay CD operates and., at contacts cd2, cd3 sends a long negative start impulse over line L1, L2, after which short impulses are sent under control of relay CSA. These impulses are negative until switch CS reaches position 5 or 6, one of which is selectively marked by strappings between banks CS3 and PS3 (see table A), whereupon relay CP pulls up and reverses the polarity of the impulses. In a similar way, a. second marking by strappings between banks CS3 and PS4 later bring about the temporary operation of CN and the release of CP to restore the original polarity. Relay CP again operates at contact 17 of switch CS to end a positive, end of selection, pulse. Over contacts 18 to 24 of switch CS relay CD again operates to transmit a long control pulse, this being positive if CR. is operated or negative if it is released, since in the latter case relay CP is released by CN on contact 18 of switch CS. Finally, relay CX energizes on contact 25 of switch CS and locks unless key CK or TK has previously been restored. Switch CS now goes to contact 1 and the circuit is returned to normal by the release of PH by resetting key RSK. Controlled station. Relays IN, IP, Fig. 2, respond to negative and positive pulses -respectively and on receipt of the negative starting pulse relays G, C and GA operate in that order. The negative pulses step switch RS and according to whether one or two negative pulses are received in the first group the positive impulses are counted on switch AS or BS respectively, these switches being arranged to move two steps per positive pulse. The second group of negative pulses advances switch RS. A check on the total number of selecting pulses is made by means of cross-connections between banks RS2, AS3, BS3 (see table B) and if this is correct, the positive end of selection pulse operates relay GC which releases relay C and prepares the appropriate two control circuits, one of which is completed by the response of relay IN or IP to the final control pulse. The sending of supervisory signals from the controlled station, during the receipt of signals, is prevented since the operation of relay C during this time disconnects positive from the indication sender. The system may be extended to control any number of switchgear units by adding further switches similar to AS, BS, each serving ten additional units.