Track Circuit Interrupter - Insulated and Non-insulated Interrupters

Insulated and Non-insulated Interrupters

Originally, track circuit interrupters were directly connected to the rail, both physically and electrically. One of the track circuit tail cables would be connected to the interrupter, it being connected to the rail. If the interrupter was broken, it was possible that the broken part, with cable still attached, could drop onto the rail and allow the track circuit to remain energised and show 'clear'. To overcome this, it is now practice for track circuit interrupters to be insulated from the rail to which they are attached. A track circuit cable is taken via the interrupter, with one end connected to the upper part of it and another end to the lower part. The cable is at opposite polarity to the rail, therefore should the broken part of the interrupter drop onto the rail, the track circuit will be short circuited and show 'occupied'.

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