QGSTAR Model 8822 Wireless Digital Infrared Monitor Sensor Detector Entry Welcome Alarm Doorbell wireless infrared alarm, consists of two parts: sensor & receiver. Alerts you when someone enters your driveway, such as visitors, vehicles, intruders, animals or kids coming or going! The working distance is 400 feet away. Signal sent via IR, cordless, battery operated, place batteries in sensor & receiver to offer power. It is very good to place in: door, porch, corridor, base room, back yard,garage etc. Scare them away! The tune set on high itself can scare unwanted visitors away.