Vktech Wireless Infrared Monitor Sensor Detector Entry Door Bell Doorbell Alarm Infrared sensor detects motion and sends a signal to the receiver Wireless installation, just place the sensor at the entrance Send audible chime sound, alerting you that somebody is approaching Working Range: Up to 100 meters / 328 feet between receiver and transmitter Ideal for front door, window frame, driveways, walk paths, and anywhere you need