Novelt'y Wireless Digital Infrared Monitor Sensor Detector Alarm Entry Doorbell Shop Store Visitor Home Entry Welcome Chime Alarm Door Bell Type Chime Welcome Music Wireless door chime is suitable for retail store, shop, business, salon, front / back / side door, etc. Attach this infrared alarm anywhere you want and instantly know when someone crosses the beam. Infrared sensor detects motion and sends a signal to the receiver. The chime is loud and clear. Receiver plug into outlet power supply, no need to install, no batteries needed. Working Range: Up to 70 meters (open field)