This is a versatile door chime for businesses that need to lock their door or are busy in the back room. When customers arrive, the motion sensor relays a wireless signal to the receiver which can be mounted on a wall or counter, or worn as a pager. It relays a signal up to 70 ft and has 8 pleasant tones. Sensor uses 3 AAA batteries (not included) and receiver uses 2 AA batteries (not included). One year warranty.