The landing door lock is a special door electric lock which is composed of two parts: mechanical interlock and electrical interlock contact. When the mechanical locks of the door electric locks on all landing doors on the elevator are locked, the electrical contacts can be connected at this time, and the elevator can be started; if there is a door on the landing door, the electric lock is not locked and the elevator is connected. Unable to move. And after the car leaves a certain floor, except for the door with a special key to unlock and open the door, the door cannot be opened by hand. This is a very important way to install the elevator in safe operation.