Deep monitoring of audio frequency track circuits

Track circuits form a critical part of the UK rail signalling infrastructure. Condition monitoring of track circuits may improve the availability of track circuits, hence improving service levels. Audio frequency track circuit condition monitoring is a relatively new concept and little work has been done on the subject. This paper describes the instrumentation of a length of active track to observe the variations in track circuit behaviour with environmental fluctuations as well as the effects of Track Circuit Assisters (TCA) on the functionality of the monitored track circuits.