"Interlock - A device having two related and interdependent functions which are:(1) to prevent the operation of the driving machine by the normal operating device unless the hoistway door is locked in the closed position. An electro-mechanical device that prevents operation of an elevator unless the hoistway doors are in the closed and locked position;(2) to prevent opening of a hoistway door from the landing side unless the elevator is in the landing zone and is either stopped or being stopped.Intermediate Landing "
