track circuit test set-up
Track circuits have the basic task of indicating the presence of a rail vehicle on a track by means of detecting a current flow through its axles. Their function is based on the closed-circuit principle. As long as there are no vehicles on the monitored track section, a current being sent by a transmitter reaches the receiver through a closed circuit including one or both rails. With the presence of a rail vehicle, the track circuit is shunted by one or more axles. As the result a current drop at the receiver is detected by means of an electromotor-type vane ralais thus indication the "track occupied" state.