Editing Interlocking (section)

=== Electro-mechanical interlocking ===
Power interlockings may also use mechanical locking to ensure the proper sequencing of levers, but the levers are considerably smaller as they themselves do not directly control the field devices. If the lever is free to move based on the locking bed, contacts on the levers actuate the switches and signals which are operated electrically or electro-[[pneumatics|pneumatically]]. Before a control lever may be moved into a position which would release other levers, a signal must be received from the field element that it has actually moved into the position requested. The locking bed shown is for a GRS power interlocking machine.