Electrical Detector

Railway Signalling Electrical Detector

Basic Concepts of Railway Signalling

Electrical Detector

Electrical detector is an electro mechanical 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 center, 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.

Electrical Detector

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.

Point position  normal detection  reverse detection  normal shunt  reverse shunt 
Point normal & unlocked        open open made open
Point normal &  locked        made open made open
Point reverse & unlocked        open open open made
Point reverse & locked        open made open made


Electrical detector|Shunt|Detection contact position during & after point operation

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