Patent GB-650400-A (GB)
Title: System for the determination by radio means of the distance between two railway vehicles
IPC: B61L3/12
Filed: 1948-05-25
Abstract: 650,400. Railway signalling apparatus. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. May 25, 1948, No. 14074. Convention date, Sept. 23, 1947. [Class 105] [Also in Group XL (c)] Relates to a system of the type illustrated in Figs. 1-3 (not shown) for indicating on a train A the distance ahead of a train B on the same track comprising an interrogating pulse radar located on train A operating in conjunction with a responder on train B, the interrogating and reply frequencies being F1 and F2 respectively. According to the present invention an auxiliary transmitter and receiver operating at frequencies F1 and F2 respectively, are provided at both the interrogator and responder for giving a visual and aural warning when the equipment is faulty or when the two trains are within a predetermined range, e.g. 3,000 yards. As shown in the Figure, pulses of carrier frequency F1 are radiated from the interrogator transmitter 12 on train A controlled by the keyer 10, received by the responder receiver 24 on train B, relayed by the responder transmitter 28 at a carrier frequency F2, received by interrogator receiver 16 and applied to give a type-A display on the cathode-ray tube 22 whose time-base generator 20 is synchronized by the keyer 10. The interrogating pulses are also received directly by the auxiliary receiver 44 at train A and applied intermittently to the auxiliary trans-. mitter 48 through contact 60 of the code relay CTA operating at a frequency of 3c/s. and through contact 64 and/or contact 66 of relays CRA and DRA. The intermittent groups of pulses radiated by auxiliary transmitter 48 are received at receiver 16 whose output is applied to operate relay DRA intermittently in correspondence with the operation of code relay CTA, thereby continuously energizing relay CRA which closes contacts 62, 64 and 80. Contact 62 completes the circuit of a lamp KA which lights to indicate that the interrogator transmitter and receiver are functioning correctly and contacts 64 and 80 constitute holding contacts. A further indication is provided by applying a negative blocking voltage B( - ) to the grid 68 of the cathode-ray tube via contact 78 of the code relay CTA and via contacts 80 and/or 82 of relays CRA and DRA causing the trace to flash intermittently. If the transmitter 12 and receiver 16 fail when the train separation is greater than the maximum distance at which the interrogating pulses can trigger the responder, the relay DRA will not be energized; also if transmitter 12 and receiver 16 are functioning correctly and the trains approach within the operating range, the continuous train of reply pulses from the responder will cause relay DRA to be continuously energized, but in either case relay CRA will be de-energized, thereby breaking the circuit to the indicator lamp KA, stopping the intermittent flashing of the cathode-ray trace and completing the circuit to the aural alarm XA. The responder includes a similar auxiliary transmitter 54 and receiver 56 and corresponding relays CTB, DRB, and CRB, the H.T. supply B (+) for the transmitter 52 being applied through contact 70 of the intermittently-operated code relay CTB so that when the responder is not within range of the interrogator, transmitter 52 radiates continuously during the intermittent periods when contact 70 is closed and the intermittent signals received at the auxiliary receiver 56 via the responder receiver 24 and transmitter 28 cause a corresponding intermittent operation of relay DRB which causes relay CRB to be energized continuously, thus completing the circuit to lamp KB, which indicates satisfactory operation of the responder. If receiver 24 or transmitter 28 fails, the relay DRB will be inoperative and if transmitter 28 is unstable so that it radiates continuously or if the responder is being actuated by a continuous train of pulses from the interrogator, relay DRB will be continuously energized; in either case relay CRB is deenergized, thereby breaking the circuit to indicator lamp KB, completing the circuit to the aural alarm XB and de-energizing auxiliary transmitter 52.