Laser trip wires are a common method of detecting intruders, in movies that is. They aren’t so commonly used in standard security systems simply because there are more effective methods of detecting movement. Nevertheless, understanding how they work can be helpful in getting a grasp on more complex security methods.

A laser tripwire alarm works by using a laser beam generated by a diode. The laser is angled in a way so that the beam continuously strikes over the light dependent resistor sensors. If something crosses the path of the beam, it blocks the laser from reaching the resistor sensors. This is all picked up by a controller, which sends a signal to power on the buzzer.

Lasers themselves are used in many different areas of security, including range-finding, target illumination, monitoring of hazardous gases, and illumination. They are are common tool in military and defensive applications due to their accuracy and utility.