1. This product is a PIR sensor switch, it is usually installed in the public place or the corridor of house, in the conditional weak light, when people arrive, and it turns on. When people leave, it turns off with delay. 2. When the light is bright enough, it will not turns on, it is energy saving. 3. It can be used in alarm system, if we install it in the forbidden area, the alarming dell will ring when someone invades into the area. 4. It also can be used in corridor, stair hall, balcony, washroom, garage, etc.