Simple to build kit emits a tone which changes with amount of skin resistance between two fingers. If you are relaxed, a lower pitched tone will be heard. Fun to use and great for parties. Features 2 copper touch plates on circuit board and small speaker. A fun "poor man's lie detector"! Operates from 9V battery (not included). Size of circuit board: 2" square. Complete with all parts, PC board and instructions. Skill Level 1.