PURPOSE: To facilitate work by unnecessitating the position matching of a hook when fitting a case to a work plane such as a wall surface or the like.

CONSTITUTION: A case 1 is equipped with the operation part of switches SW1, SW2, and SW3 on the front face and a signal transmission window 17 for the transmission of wireless signals at a peripheral required point. By screwing fixed screws through two fitting holes 21 provided at a fitting plate 2 to the work plane, the fitting plate 2 is fixed to the work plane. On the front face of the fitting plate 2, a pair of hookers 22 are projected while being protruded forward and protruding the heads upward. On the back of the case 1, a pair of hook holes 13 are formed to freely attachably and detachably couple the case 1 to the fitting plate 2 while being engaged to the respective hookers 22.