To solve the problem that a tamper switch does not operate when an attaching plate is detached from the ceiling or a wall surface together with equipment in the state that the attaching plate and an equipment main body are connected regarding an interference action detection mechanism for ceiling/ wall surface installed type equipment.

A plate material held in the state of being floated for a prescribed distance by an elastic member (spring) is provided on the outer side (installation surface side) of a base member for fixation and the plate material and an actuator of a switch are brought into contact in the state of installing the equipment.