Railway signalling system

Claim 1

A railway signalling system comprising: a permanent magnet positioned on a railway track at a point preceding a multi-aspect signal, an electro-inductor and an antenna means positioned in sequence directly following said magnet in the intended direction of movement of a train along said track, means for energising said electro-inductor with a d.c. supply and said antenna means with a high frequency signal in dependence upon the present aspect of the signal, detector means carried by a railway vehicle for detecting the fields produced by said magnet, by said electro-inductor and by said antenna means to provide a warning to a driver of the train corresponding to the present aspect of said signal, said detector means including a first and second inductive pick-up coil, said first pick-up coil being adapted to detect the static magnetic field produced by the permanent magnet and by said electro-inductor, and said second pick-up coil being adapted to detect the high frequency alternating magnetic field produced by said antenna, said first coil being connected by way of a logic unit to a first and second alarm means, first acknowledgement means for said second alarm means, said second coil being connected to a relay coil whose contacts connect said logic unit to a second alternative acknowledgment means for said second alarm means, said logic unit in response to detection by said first pick-up coil of a signal from said permanent magnet along actuating said second alarm means to thereby require the train driver to operate said first acknowledgment means to prevent automatic application of the train brakes, said logic unit in response to detection by said first pick-up coil of a signal from said permanent magnet followed subsequently by detection by said second pick-up coil of a signal from said antenna means controlling said relay unit to operate and thereby control said logic unit to actuate said second alarm means to thereby require the driver to operate the second acknowledgment means to prevent automatic application of the train brakes, and detection by said first pick-up coil of a signal from said permanent magnet followed subsequently by a signal from said electro-inductor controlling said logic unit to actuate said first alarm means which requires no acknowledgment action by the driver.