Definitions for "Motion detector"
An electronic device that senses motion within a target area and sends an alarm. Common types of motion detectors include passive infrared (PIR) and range-controlled radar models.
Control that uses passive infrared or ultrasonic detection to sense whether someone is present or not, and to turn a light on or off appropriately. Commonly used in outdoor flood or spot fixtures. "Automatic On" sensors turn lights on when presence; "Manual On" sensors require you to press a switch. Both types turn lights off automatically when they no longer sense a presence.
Motion-detector, or motion sensor, systems will automatically turn on the lights whenever anyone walks past the sensors. The motion-sensor switch simply replaces one of your standard light switches. It also has a time-delay feature, so that when you leave the area, the lights will turn back off after a pre-set time interval. The degree of motion sensitivity is adjustable also.