The idea of motion detection is a fairly simple one. A sensor is set up to detect a certain disturbance in the area, and when that disturbance is found, the motion detector sends out an electronic signal. Often that signal will travel through a security system to alert the other technology there’s motion present. This signal can do everything from setting off alarms and turning on lights to flicking the switch on a camera and turning it to face the direction of the motion that’s been sensed. Just what variety of motion sensor is used by a security system, or by a stand-alone camera, depends on what sort of motion will be captured.