How to Explain the Inside of a Motion Sensor for an Alarm System

Explain what an active motion detector is. People use active motion detectors in high security facilities, such as military installations. Active motion detectors send out an invisible laser. When that laser is disrupted by movement, the alarm sounds. Unless you know where the active motion detector is, it's impossible to avoid setting off.

Explain what a passive motion detector is. People use passive motion detectors in their driveways, front yards or to scare animals away. Passive motion sensors detect infrared energy. When the infrared energy fluctuates in an area, the motion sensor activates and turns on an alarm or a light.

Explain how the inside of an active motion detector works. An active motion detector works by bouncing a beam back and forth between two lasers. A computer inside each laser monitors this beam. If the beam is disrupted, the computer sends a signal to an alarm, which turns on.

Explain how the inside of a passive motion detector works. A passive motion detector converts infrared energy into a minuscule amount of electricity. That electricity is put through a computer, which analyzes the amount. If the amount of electricity exceeds a certain level, the computer will send an electrical charge to an alarm, activating it.