PURPOSE: To turn on/off a micro switch following insertion/removal of a key holder so as to prolong a life of the switch by arranging a rotational plate, which is energized by means of a spring, in a key box arranged in each room in a hotel and the like.

CONSTITUTION: A rotational plate 12, in which an operation part 12c is arranged at the tip, is arranged inside an approximately box-shaped key box 5 while energized by means of a spring 15. When a key holder A for the room is inserted against the force of the spring 15, the key holder A lifts the rotational plate 12, and the operation part 12c is brought into contact with a hinge lever 19 so as to operate a micro switch 16, so that a signal is transmitted for performing control of lighting and air conditioning in the room and entrance management at a front desk. When the key holder A is pulled out, the rotational plate 12 is returned to a normal position, and output of a signal from the micro switch 16 is stopped. In this way, the application of an excessive load onto the switch 16 is prevented, so that a life and detecting precision of the switch 16 can be improved.