GB1311540A - - Google Patents

Abstract

1311540 Automatic train control BRITISH RAILWAYS BOARD 22 Oct 1971 [23 Oct 1970] 50521/70 Heading B7N [Also in Division G4] A repeatedly-transmitted digital "telegram" (code message) is checked on reception using a plurality of serially-connected shift registers each sufficient to hold the information bits of the telegram, logic circuit elements comparing the contents of corresponding stages in the different registers, disparity blocking passing of information beyond the checking equipment. Each telegram includes 10 sync bits, 16 information bits and 6 parity bits, and is sent via conductors laid along the track to an aerial on a train. On the train, a sync and parity check unit passes just the information bits to the series of shift registers each having 16 stages, corresponding stages being compared in 16 AND gates also receiving an enabling signal if synchronization and parity check out. Each AND gate feeds a relay or lamp via a divide-bytwo circuit and a transformer to provide failsafe operation. Thus the train speed can be controlled or the maximum permissible speed indicated. A sync and parity check unit may precede each shift register. Train to track communication is mentioned as an alternative use of the invention.