Indoor/Outdoor Motion Detector System. Alerts you when motion is detected surrounding your home or business. Supervised Sensor: monitors the sensors and their battery condition automatically. GM-318R can work with up to 4 sensors. (additional sensors sold separately) Both audio and visual indicators. Motion detecting range: 40 feet. Operating range: 300 feet. Best of all, the House Link Motion Alert System is easy to set up, with the sensor alerting the receiver wirelessly.