This is the perfect device to scare off someone who opens your desk, dresser, file cabinet, lunch box, etc. Simply turn the arming switch to the on position. You have a couple of seconds to put your Secret Alarm in a desk and close the drawer. The next time someone opens it, a loud obnoxious noise comes from the horn until the unit is reset. Uses sensitive CDS and SCR circuit to respond to light. As long as it is kept in the dark it is quiet, but when light hits the sensor, WATCH OUT! Size of board: 3.75" x 2.25". Operates from one 9V battery (not included). Complete with all parts, PC board and instructions. Skill Level 1. C6455 ..Chaney C-6455 Secret Alarm (soldering kit)