A motion sensor (or motion detector) is the linchpin of your security system, because it’s the main device that detects when someone is in your home when they shouldn’t be. A motion sensor uses one or multiple technologies to detect movement in an area. If a sensor is tripped, a signal is sent to your security system’s control panel, which connects to your monitoring center, alerting you and the monitoring center to a potential threat in your home. The main purpose of motion detection is to sense an intruder and send an alert to your control panel, which alerts your monitoring center. Sensors work when you are not home, or when you tell the system you are not there. Some security systems can be programmed to record events via a security camera when motion is detected. Motion sensors stand guard, ready to react to various situations, such as movement in your living room, windows or doors being opened or closed, or a broken window. Motion sensors can: Alert you in the event that your teen breaks curfew Trigger a doorbell when someone approaches the front door Alert you when kids enter restricted areas in the home, like the basement, workout room, or medicine cabinet Save energy by using motion sensor lighting in unoccupied spaces Notify you if pets enter areas where they’re not supposed to be.