Fail-safe traction control monitoring to ensure the safety of signalling

The author describes the development and design of the interference monitor unit (IMU). The purpose of the IMU is to provide a fail-safe monitoring system which can be built into a locomotive´s traction control system to ensure that a train does not dangerously interfere with track signalling circuits. As an example the author concentrates on a single frequency interference monitor as used on British Rail (BR) Class 465 trains, but the basic unit has been designed to be able to be expanded to cover a number of frequencies, for different AC track circuits