Lever frame

[3]: 123 By the movement of individual levers (or sometimes cranks),[3]: 123  signals, points, track locks, level crossing gates or barriers and sometimes navigable movable bridges over waterways are operated via wires and rods.

Lever handles are usually of polished, unpainted steel, and signalmen operate them with a cloth to prevent rusting from the sweat on their hands.

This type of power frame has the disadvantage of a relatively low distance between points and signal box (approximately 200–250 m) and a slow operating speed.

The two types also share the same disadvantages such as pressurized tubing having to run directly between the field appliance and the lever frame.

Electric control of a hydraulic or pneumatic actuator in the field was far simpler and more reliable, allowing for a greater distance between signal box and points.

Whilst first being common in the United States due to work by the Union Switch & Signal corporation (a division of Westinghouse Air Brake Company), this system was later used in the United Kingdom and other Commonwealth nations where the Westinghouse Air Brake Company had a presence.

[3]: 251 In Austria, Siemens & Halske built a fully electric power frame in 1894, which does not rely on compressed air.

Unlike a mechanical linkage, pneumatic or hydraulic lines could leak and cause points to drift out of correspondence with disastrous consequences.

The Taylor/GRS electric power frame system used a feature called "dynamic indication" where the counter-electromotive force generated when the electric motor reached the limit of travel would signal the interlocking logic that the points had finished moving, but not the position of the points on an ongoing basis.

In North America this is known as "Switch-Signal" protection and any change in the position of a field appliance will immediately set the electric signals controlled by a power frame to danger.