The HS1C is a full size interlock switch in a rugged die-cast aluminum housing that also includes a locking solenoid. When mounting the key on a movable door, and the switch on a machine body, the door can be mechanically locked when closed. The door is unlocked by a solenoid lock-release signal from a PLC or other source after the machine has stopped. In the even of power failure or for machine maintenance, the door can be unlocked using a special tool.