Editing Signalling control (section)

=== Lever frame ===
{{main|Lever frame}}
[[Image:Leverframe.jpg|thumb|right|A mechanical lever frame inside the signal box at [[Knockcroghery]] in [[Ireland]]]]
The earliest signal boxes housed mechanical lever frames. The frame was usually mounted on a beam beneath the operating floor. [[Interlocking]] was attached to the levers, which ensured that signals showed the correct indication concerning the points and were operated in the right order. Wires or rods, connected at one end to the signals and points and the other to levers in the signal box, ran alongside the railway.

In many countries, levers are painted according to their function, e.g. red for stop signals and black for points, and are usually numbered, from left to right, for identification. In most cases, a diagram of the track and signaling layout is mounted above the lever frame, showing the relevant lever numbers adjacent to the signals and points.

Hand-powered interlockings were referred to as 'Armstrongs' and hand throws in the United States.

'''Power frames''' have miniature levers and control the signals and points electrically. In some cases, the interlocking was still done mechanically, but in others, electric lever locks were used.

In a few cases, signals and points were operated pneumatically upon operation of the appropriate lever or slide.