256 Selectable code numbers prevents outside interference. Weather proof for outdoor use. 256 Selectable code numbers prevents outside interference. Transmission range of up to 150 feet (45 Meters) Weather proof for outdoor use. Red light indicates battery is good.A magnetic sensor/transmitter to detect anyone open the door with sounds. The unit is activated the moment the magnetic sensors move apart from the other more than ½ of an inch.Power by a 12-Volt Alkaline battery, type A-23 or MN-21 (included)  Can be mounted with screws or double-sided tape (included)

Wireless Doorbell