Don't let anyone sneak into your room undetected! Build your own Intruder Alarm to keep out those pesky brothers & sisters! And while you are at it, explore how a magnet sets off this cool build-your-own intruder alarm. It's a great project for exploring how a magnetic switch works in an electric circuit. Simple construction of the alarm box is required. Requires 2 x AAA batteries. Ages 5 and over.