GB840011A - A railway automatic block signalling system employing track circuits - Google Patents

Abstract

840,011. Railway automatic block signalling systems. COMPAGNIE DE SIGNAUX ET D'ENTERPRISES ELECTRIQUES. Aug. 9, 1957, No. 25251/57. Class 105. In a railway automatic block signalling system employing track circuits with continuous rails each block section comprises two track circuits operating at high frequencies and between them at least one track circuit of any desired length and operating at any desired frequency. Each track circuit A, B, C; A<1>, B<1>, C<1> has a transmitter E1, E2, E3, &c. at the exit end of the track circuit and a receiver R1, R2, R3 &c. at the entrance end, the receiver, R2 &c., in all track circuits except the one at the entrance end, controlling the transmitter E1, E2 in the preceding circuit as regards direction of train travel. One or more of the receivers such as R1 and B<1>, the entrance end receiver, controls a relay r<1>, which in turn controls the entrance signal 3 to the block when no transmission is received from the associated transmitter, e.g. E1, because of a train in the section B, or A, which short-circuits the transmission of the section the train is in, resulting in the blocking of the transmitters by their adjacent receivers, e.g. through relay contacts or direct application of potentials. The transmitters may comprise pentode or transistor oscillation generators (Figs. 2, 4, 5, not shown). The frequencies employed in each of the track circuits A, B, C, are so determined that the effective lengths of the track circuits A and C do not overlap substantially the effective length of the circuit B and the block section protected by signal 3 is bound by the points of connection to the rails of the receiver R1 and the transmitter E3, with a degree of precision dependent upon the high frequencies employed in track circuits A and C.