GB997685A - Track circuit - Google Patents

Abstract

997,685. Track circuit. GENERAL SIGNAL CORPORATION. July 23, 1963 [Sept. 7, 1962], No. 29109/63. Heading B7N. In a track circuit in which the track rails 3 are supplied with current from a D.C. source 1 via resistor 2, the current flowing in a winding 13 in the output of the circuit in the absence of a train controls, via a pair of cores 10, 110, each formed of a material having a substantially square hysteresis loop, the alternate energization and de-energization of relay 115 from R.F. generator C whereby a relay 15 is continuously energized to signal the absence of a train. The output from clock pulse generator A threads minor aperture 11 on core 10 and major aperture 109 on core 110 and acts to set core 10 and clear core 110. The output from generator B at the same frequency as generator A but shifted in phase therefrom threads major aperture 9 on core 10 and acts to clear the core. The occurrence of a setting pulse for core 10 and the presence of priming current from the track section sets up an anticlockwise flux path around minor aperture 12 and the subsequent clear pulse from generator B reverses the flux direction in the outer limb of the aperture and induces a signal in loop 14 which sets core 110 so that the output of RF generator C induces a signal in loop 114 which, after rectification, operates relay 115. The next clear pulse from generator A prevents the transmission of RF energy to loop 114 and the relay releases. Alternation of relay 115 picks up and holds relay 15. The presence of a train or a fault in the circuit stops the of relay 115 and relay 15 subsequently releases.