The PIR Sensor detects motion up to 20 feet away by using a Fresnel lens and infrared-sensitive element to detect changing patterns of passive infrared emitted by objects in its vicinity. Inexpensive and easy to use, it's ideal for alarm systems, motion-activated lighting, and holiday props. The PIR Sensor is compatible with all Parallax microcontrollers. BASIC Stamp and SX/B code is avaliable under Downloads below, and Spin code is posted to the Propeller Object Exchange.