Don't have any of those luxurious security systems? Lack of budget? You can have your own now without spending too much!
Step 1: Materials Needed
For the battery, we used battery out of coins and foil (the one I posted a while ago).
Step 2: Schematic Diagram
Step 3: Connect the Parts.
Solder the parts according to the schematic diagram. Then put in a place where in it is hidden. In our case, we put it in a flower designed pen. I wrapped some parts of it with a electrical tape to secure them properly.
Step 4: Test It.
As you turned on the switch, the buzzer rings continuously but when you point a laser on it the ringing sound will stop. Multiple reflections can be created by using mirrors to make it more complicated just like in the movies. :)