The purpose of an interlocking is to ensure that only a safe disposition of points and signals can be deployed. Not only is it designed to allow good things to happen, but also to prevent bad things from happening, in the latter instance by ignorance, accident or malicious intent.

The mechanical interlocking is achieved through the attachment of notched vertical tappets, connected through the floor of the upper signalbox room, to their respective levers. The tappets are held in a frame through which are fitted a number of locking bars that have locks on them that engage with the notches in the tappets, as appropriate, to achieve the necessary degree of protection. In a addition some levers may be fitted with electrical locks.

The following "Signalbox" allows the user to operate the signals in accord with the above principles by clicking on the various levers. The mechanical arrangement for the interlocking to support this arrangement is also shown. Note that the interlocking is achieved by the use of notched metal bars (tappets) attached to the levers, with locks that engage with those notches to release or lock levers as appropriate. (Roll up the screen to make sure that you can see the comment box at the bottom. It reports on the status of your attempts to pull the levers! If you get an error, simply try another lever.)

Distant   Home Station Area Starter
8   9   10

8   9   10
Signalbox Lever Frame

Current Interlocking disposition