Patent GB-967795-A (GB)
Title: Improvements relating to remote control and/or indication systems
Inventor: WHITE EDGAR IAN
IPC: B61L7/08
Filed: 1960-02-12
Abstract: 967, 795. Electric selective signalling systems. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. Feb. 13, 1961 [Feb. 12, 1960], No. 5021/60. Heading G4H. In a continuously scanning remote control and/ or indicating system means are provided at each station for reducing the time log between the occurrence of a change in the state of a control or indicating element, e.g. a switch, and transmission of the new state of the element. In the system described, the control station comprises 100 registry stages and 100 transmission stages divided into ten groups of ten stages each. The groups are normally selected in succession by counting chains B1-B10 a scan of the ten gates &1-&10 &c. and registry stages 1-10 &c. taking place between each group selection by means of counting chains A1-A10. If during the scan of group 1, say, a control switch in group 8 is changed over, the state of bi-stable circuit E8 is changed, and at the end of the group scan which is proceeding, counting chain B1-B10 selects the groups in succession without intervening group scans until group 8 is reached, this group then being scanned in the usual manner. Distributer D normally supplies eleven consecutive clockpulses to counter A1- A11 to each pulse supplied to counter B1-B11, but when one or more of circuits E1-E10 are set, as soon as the count reaches stage A11 the next successive clock pulses from generator C are routed to B1-B11. Each circuit E1-E10 is connected over a lead f to the corresponding counter stage B1-B10 so that when the count reaches B8, in the example chosen, circuit E8 is reset to send a pulse over line g to change the state of bi-stable circuit G and render transistor TR non-conducting. This prevents any earth clamp applied to line e by another of circuits E1-E10 which has been changed over, from preventing the scanning of group 8. At the end of this group scan any other "priority" calls are dealt with in a similar manner. The states of the control switches are transmitted as frequency W or frequency X by means of transmitters TW, TX controlled by the signals on leads C1, C2. At the same time the states of switches at the remote stations are transmitted to receivers RY, RZ at the control station as frequency Y or frequency Z and are set into registry stages 1Z or 1Y to 100Y or 100Z. Each remote station is similar to the control station but only a limited number of control registry stages and indication switches are provided at each station, corresponding, for example, to 25 successive count periods of the complete scanning cycle. When a normal group scan is proceeding frequency B is transmitted to the remote stations from transmitter TB, and receivers RB set circuits G so that transistors TR are non-conducting. If one or more of circuits E1-E10 at the control stations are set, transmitter TA transmits frequency A and receivers RA impose an earth clamp on lines e at the remote stations to signify that a "priority" call is to be made as described above. The remote stations are also capable of making a "priority" call to the control station in the same way, the transmitters and receivers TA, RA and TB, RB being interlocked to preventsimultaneous transmission of frequencies A, B. Priority calls may be dealt with in strict order, irrespective of whether they originate from the control station or a remote station, or either control or indication priority calls may be given preference by suitably interlocking the transmitters and receivers for frequencies A, B.