GB1412243A - Track signalling apparatus - Google Patents

Abstract

1412243 Determining train position ERNEST F MOY Ltd 18 Aug 1972 [21 July 1971] 34256/71 Heading B7N Apparatus for determining the position of a train on an electrically continuous track comprises an arrangement for applying a signal to the track at each of a series of locations in sequence receive elements at the locations for measuring the received signal at locations adjacent to the location to which the signal is applied and a comparator for comparing the received signals with stored signals having values which would be received at the locations in the absence of a train. The apparatus at the locations is controlled from a central office which is connected to the locations by address cores, data lines and a power cable. The locations are addressed in sequence from the central office and on receipt of its address a decoder D1 at a location issues signals to bias on FET's 1 and 2 whereby the output of oscillator 01 is applied via operational power amplifier OA1 and tuned transformer T1 to the rails of the track. At the end of the transmit period at a given location the address of the next location is sent and this when received at the given location is read by decoder D2 which acts to restore FETs 1 and 2 to their non- conducting state and also biases on FET 3 whereby the amplifier OA1 acts to maintain the transformer current at zero so the circuit as seen from the rails presents a high impedance. During the time a location transmits to the rails the voltages received at, e.g. four locations to each side of the transmitting location are transmitted in turn to the central station. The voltage is obtained from the primary winding of the transformer T1 and applied via a rectifying circuit and an A/D converter to a series of gates G1-G5 which are biased on when a further address signal from the central office is read by decoder D 3 . The digital representation of the voltage is then applied via line drivers LD1-LD5 and the data lines to the central station.