a simple electric device to detect the presence of trains on the track, which can be used to inform the signalmen, and to control the relevant signals

A means of detecting trains or vehicles by passing an electrical current through the rails, which is diverted by the presence of vehicles whose wheels and axles form an electrical path from one rail to the other. First devised in the 1890s track circuiting was introduced only slowly (mostly from 1910 onwards) as the widespread use of Mansell coach wheels with wooden centres prevented the track circuit from operating, thus nullifying this important safety feature.

An electrical circuit of which the rails of the track form a part. The track circuit is the basis of signaling systems.