The Ideal Security QH series wireless motion sensor detects motion and triggers an alarm at the receiver unit (sold separately). The alarm has loud alarm (100dB), soft chime, and silent (flashing lights) modes. Monitor driveways, gates, sheds, walkways, and swimming pools. Monitor front or back doors at small businesses, or supervise children to keep them safe. The motion sensor works in both light and darkness, but it is not pet immune.The range from the sensor to the receiver is up to 120 meters (390 feet). The sensor's viewing angle covers an arc of 45 degrees and detects motion at a distance of 5-8 meters (16-26 feet).The motion sensor can be fastened to the wall using the screw keyholes on the back, or can be kept portable. It can be installed indoors or outdoors. When installing outdoors, try to shelter it from direct downpours. Up to 50 sensors can be linked to the alarm unit (sold separately). 3 AAA batteries are required and are not included.