Individual Function Switch

This page explains the concept of an Individual Function switch panel and compares it with mechanical and electric lever frames.

Individual Function Switch

Individual Function Switch

Individual Function Switch. The switches, which are free to move, operate Normal and Reverse lock relays. The lock relays only operate when the interlocking allows them to do so. The lock relays de-couple the switches from the interlocking (compare this with the Electric Lever frame).

Signal Lighting. If a signal lock relay is Normal the signal MUST be displaying STOP but the converse does not necessarily apply - the signal indication is determined not only by the state of the signal lock relay but also the occupation of track circuits and the setting of points.

Mechanical Frame. In a mechanical frame the levers are mechanically interlocked.

Electric Lever Frame. In an electric lever frame, such as the style-L in A-Box, the interlocking is a mixture of relays and electric locks on the levers.

The levers can only operate when it is safe for them to do do. Points levers are held in a checkleck position until the points have fully moved and it is safe to free the interlocking.

Last Updated: Tue Nov 13 16:46:13 NZDT 2012

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