A mechanical locking device on each floor landing door that prevents the door from being opened unless the elevator car is correctly positioned at that floor.
Full Definition
The landing door lock (also called the interlock or landing door electromechanical device) is a dual-function device: it mechanically locks the landing door against opening from the landing side when the car is not at the floor, and simultaneously provides an electrical contact that is part of the safety circuit. Both the mechanical lock and the electrical contact must be in the closed (locked) state for the elevator drive circuit to be energised. If any landing door is opened or improperly locked, the drive circuit opens and the elevator stops. EN 81-20 specifies that the door lock contact must only be bridged by the car when within the unlocking zone (typically 200 mm above and below the floor level). This prevents passengers from opening landing doors and falling into the shaft when the car is elsewhere.
