Patent GB-643524-A (GB)
Title: Improvements in or relating to electric signalling systems
Inventor: D ASSIS-FONSE HAROLD MOUNTJOY
IPC: H02J13/00
Filed: 1947-12-17
Abstract: 643,524. Electric selective signalling. STANDARD TELEPHONES & CABLES. Ltd. Dec. 17, 1947, No. 33290. [Class 40 (i)] A sub-station and a central station are connected by a two-wire line, and a sustained signal from the sub-station causes the central station to send back a sustained answer signal which causes the sub-station to terminate its sustained signal, this termination causing the central station to terminate its answer signal. General description.-A sub-station has, e.g., five contacts, whose positions are sequentially notified to a control station by a train of signals initiated by the control station or by a change of position of any one of the contacts. Each signal of the train persists until the substation receives a responding signal from the control station. A fault on the line is indicated at the control station, and on repair, the substation signals its contact positions to the control station. Signalling position of contacts.-When one of the contacts 1 ... 5, Fig. 1, at the substation changes its position, the charge on the associated condenser is reversed, thus actuating relay L which locks on its second winding and actuates relay S ; relay S locks and releases relay L, and over contacts S3, S4 actuates relay SP which connects positive to line LE1. This signal at the control station, Fig. 2, actuates relay P which operates relay PA which prepares the circuit of relay ON at contacts pa2 and actuates relay SA over contacts pa1 and ee1 ... aa1; relay SA locks, prepares the circuits of relays ON, SR, and actuates relay G which operates relay ON; relay ON locks, shunts and deenergizes relay P and de-energizes relay G so as to actuate relay SR which puts positive on line LE2. At the sub-station, this signal operates relay RN which actuates relay PC to operate relay OJ which locks, connects resistances YF, YG so that relays SN, SP are connected to a point of zero potential, operates relay A and completes a holding circuit for relay S over its right-hand winding; relay A releases relay SP and thus terminates the positive signal on line LE1. At the control station the cessation of signal from the sub-station releases relay P, which releases relay PA, which locks, and actuates relay AA to release relay SR and disconnect positive from line LE2. At the substation, the cessation of the signal from the control station releases relay RN which releases relay PC to release relay S but leaving relay A operated over its contact a2; relays SN, SP are now in a condition to respond according to the position of contacts 1; as shown, relay SN operates to connect positive to line LE2. This signal, at the control station, operates relay N which actuates relay NA which releases relay SA, relay AA holding over its right-hand winding. Positive is thus connected over contacts aa3, pa2, na2, aa5 to the release winding R of latching relay LA; if relay LA is already unlatched, relay SR is actuated, and if relay LA is latched, it is unlatched and again actuates relay SR. Relay LA also lights the appropriate lamp GL1, RL1 to register the position of contacts 1 at the sub-station. Relay SR connects positive to line LE2. At the substation, this signal operates relay RN which actuates relay PC to operate relay B in series with relay A.. Relay SN is released disconnecting positive from the line LE2 so that at the control station relay N is released to release relay NA to operate relay BB and releasing relay SR to remove positive from line LE1. This causes the sub-station to respond by releasing relay RN to de-energize relay PC which releases A but leaves relay B actuated so that one of relays SN, SP operates to send a signal according to the position of contacts 2. This interlocked signalling continues until all the contacts 1 ... 5 at the sub-station have had their positions registered on the lamps GL1, RL1 ... GL5, RL5 at the control station, from which the last signal actuates relay Z in the sub-station which locks and disconnects relays A ... E, thus breaking the circuit of relays SN, SP and de-energizing the line. This results in the release of relay N or P at the control station to release relay NA or PA which releases relays EE, ON which connects a line proving feed to the line LE1. This feed operates relay RP at the sub-station which releases relays OJ and Z to restore the circuit to a normal waiting condition. By depressing key CK at the control station, the line proving feed is interrupted to release relay RP at the substation to actuate relay S which operates relay SP and thus initiates the signal train. Fault indication.-A line fault interrupts the normal line proving feed to stimulate the substation to start the signal train, as indicated for the opening of key CK. But the first signal obtains no reply and the sub-station waits. At the control station if the fault is a short-circuit, the current in the lower windings of relays N, P exceeds that in the upper windings and its direction is such that relay N operates to actuate relay NA; since relay ON is not operated, relay NA actuates relay LF which disconnects the line proving feed and lights fault indicating lamp FL; the removal of the line proving feed releases relays N, NA, but relay LF holds over its contacts lf2. If the fault is a discontinuity, relay P operates to actuate relay PA which operates relay SA to actuate relay G which energizes relay ON to lock and de-energize slow-release relay G just as for a normal signal; relay ON removes the line proving feed at contacts on1, releasing relays P, PA before relay G releases, so that relay LF is actuated and to light lamp FL, and release relays ON, SA. When the line has been repaired, the positive feed from the sub-station causes the resumption of signalling.