How Do Alarm System Motion Sensors Work?


Motion detectors are an invaluable part of any custom home security system, but few people outside the industry understand how they work. Don’t worry, we’re not giving away any tips here that could help burglars, just providing you a basic understanding of how motion sensors function.

There are two basic types of motion detectors…

Active Motion Sensors

Active sensors work like radar, sending out ultrasonic waves that then bounce back to the sensor. When interpreted by the sensor, the waves produce a virtual picture of the surrounding area. If something changes in the space – a person walking by, for example – the detector is triggered. It then signals a receiver to initiate an action, such as turning on a light, opening a door or, in the case of a home security system, sounding the alarm.

Passive Motion Sensors

Passive sensors generally detect variations in either heat or light. Passive infrared (PIR) motion detectors sense the body heat produced by people and animals. When the sensor is armed, any sudden change in this infrared energy will trigger the detector. With photo motion sensors, an invisible laser beam connects two terminals, often on opposite sides of a room, or across a doorway or hallway. When something passes through and interrupts the beam, it triggers the detector.

Both active and passive motion sensors provide a real obstacle for would-be criminals. It’s very difficult for a burglar to pass through a room equipped with either one, even if he’s aware they’re in use.

At Scott Alarm, our complete home security package includes an in-home motion detector, as well as multiple door and window sensors, a wireless control panel, yard signs and much more. And with 24-hour monitoring, we’re always standing by to send help your way in case of an emergency.

We’ve protected Jacksonville families for nearly 50 years, and we’ll be by your side for years to come.

Contact Scott Alarm today to schedule your free custom home security consultation today. We’re local people, so we’re here when you need us most.