The electrical detector is an electromechanical device to check the position for correct setting and locking of points through making an electrical contact, which closes a circuit. It has two sets of fixed contacts. In centre, bridging contact assembly on a roller cam shaft, which works in conjunction with the points and lock slides, makes the fixed contact as per the point setting.

Point operating member (i.e., lever position) in the circuit ensures correspondence between lever position and point detection.. Normal shunt and reverse shunt contacts in the circuit ensure the conflicting relay is not energized from false or cross feed to ensure safety.

Shunt & Detection contact position during & after point operation.