To start operation of an apparatus system to be controlled according to an order required from the point of securing safety, by turning on or off a first switch unit by pressing a key, and turning on or off a second switch unit during rotation of a changeover rotor.

A switch unit 11 is placed on the side of the rear part of a key unit 1, and another switch unit 16 is fixed to the just back of the key unit 1. The switch unit 16 is first turned on by pressing a key 10 inserted into a locking rotor 13 against energization by a spring 18, and then the switch unit 11 is turned on by rotating the key 10. For securing safety of an apparatus system to be controlled, the switch unit 16 is assigned as a switch of an apparatus to be first turned on, and the switch unit 11 is assigned as a switch of an apparatus to be next turned on.