Model signal frame, scale 1:4, Chambers' signal interlocking frame.

In order to prevent accidents at railway junctions it was soon found necessary, as traffic increased, that the points and signals should be mechanically connected. This would prevent conflicting signals being made and errors occurring which could have fatal consequences.

This model represents the interlocking frame patented by Mr A Chambers in 1860.

The frame is designed for a simple junction of a double line and the tops are arranged so that the main or branch signals cannot be lowered until the points have been moved into the correct positions, and no conflicting signals can be lowered together.