PURPOSE: To eliminate the cost for wiring construction and to prevent illegal use by making a buzzer for illegal use sound by a room controller if a key of each room is detached without inputting it to the room control device in a reception office.

CONSTITUTION: A master equipment and slave equipments use the same key set and the master equipment is connected to a computer. Namely, 'KARAOKE' (orchestration without lyrics) in 'KARAOKE' rooms and the room controller 5 in the reception office 1 are connected, and keys matching the keys of the 'KARAOKE' rooms are prepared at the room controller 5. Then the key prepared in the reception office 1 is carried and sets to the key of the 'KARAOKE' room to turn on the power source, and the lighting fixtures and equipments in the room operate; if the key of the 'KARAOKE' rooms is detached without setting the key to the room controller 5 in the reception room 1, the room controller 5 makes the buzzer for illegal use sound. Therefore, the illegal use of the room in a building wherein the 'KARAOKE' equipment 3 is installed can be prevented.