Patent GB-679786-A (GB)
Title: Improvements relating to remote control systems
IPC: G08B25/00
Filed: 1950-09-19
Abstract: 679,786. Electric selective signalling. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., and GROSE, B. H. April 10, 1951.. [Sept. 19, 1950], No. 22939/50. Class 40 (i). In a remote control system comprising a number of field stations selectively controlled by coded signals over a pair of line wires from a central office, e.g. as described in Specification 629,984, change-over means are provided at the office and at each field station for transferring the code-signalling apparatus from the normal line circuit to a standby line circuit, a failure of the normal line circuit being automatically signalled over the standby line circuit to cause operation of the office change-over means. As shown in Fig. 1, the polarized line relays R at all field ststions, only one of which is shown, are normally energized over the normal line.4, 5 from battery 1 at the office, and control signals from the office to a field station or indication signals from a field station to the office sent in a known manner (not shown). In the event of a fault e.g. a break in one of the line wires 4, 5 the normally energized fault detector relays W and the line relays R at all field stations beyond the fault are de-energized. At each of these stations, the line relay R, as it falls off, de-energizes its associated repeater relay RPA which releases only after a time interval sufficiently great to prevent its release during code signalling. The repeater relay RPA, as it falls off releases the normally energized change-over relay X whereby all stations beyond the fault are switched over from the normal line 4, 5 to the standby line 6, 7. The office fault detector relay Y is then energized from battery 20 over the standby line 6, 7 in series with the line relays R at the stations beyond the fault, but these line relays do not operate, however, because the line current is reversed relative to the normal line current from battery 1. Relay Y energizes the change-over relay Z at the office to switch the code signalling apparatus to the standby line 6, 7. Relay Z at the same time locks at Z 16 and disconnects battery 20 from the standby line 6, 7 whereupon the line relays R at all field stations are energized from battery 1. and normal code signalling may be effected over the standby line until the fault is corrected. Breaking the locking circuit of the change-over relay Z by a manually operated reset switch then reverts the circuit connections to normal. Alternatively, the office fault detector relay Y may operate a lamp indicator, upon the occurrence of a fault and the change-over at the office to the standby line then effected manually. Modifications. In Fig. 2 (not shown) the signalling back over the standby line to the office to change-over the relay Z thereat is effected only from the field station at the remote end of the line. The application of the invention to a system employing a sectionalized line circuit e.g. as disclosed in Specification 589,332 is also described in Fig. 3 (not shown). The standby line circuit may be used for other signalling purposes when the normal line circuit is intact or, by the use of filter circuits, may be used for such other purposes continuously.