The Ideal Security QH series wireless alert uses a motion sensor to detect motion and sends a wireless signal to the linked receiver. Once a signal is received by the receiver, the unit will chime, alarm (100dB) or just flash lights. 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 alarm has 4 alert settings: Loud alarm, Loud chime, Soft chime, Lights only. To scare off intruders, choose the high-decibel alarm. In situations where movement must be restricted, this alarm set can provide a gentle chime indication to warn others. Use the lights-only mode to silently keep an eye on movement in areas of your home, shop, or place of work. 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 receiver has an on and off switch and volume control for the alarm and chime. Both units can be fastened to the wall using the screw keyholes on the back, or can be kept portable. The motion sensor unit can be installed indoors or outdoors. When installing outdoors, try to shelter it from direct downpours. The alarm unit is designed for indoor applications only. Set includes 1 PIR motion sensor unit and 1 receiver / alarm unit. Up to 50 sensors (sold separately) can be linked to the receiver (SK602-1). Batteries are required and are not included: 3 C batteries for the receiver and 3 AAA batteries for the sensor. An AC adapter is available for the alert unit, sold separately (SK600CHG1).