Simple to build kit creates a tone which varies depending on the amount of light you allow to strike on a CDS cell. Kit features IC circuitry and small speaker to create this unusual effect. In total darkness the unit is silent; as light increases the kit emits clicking sound then with more light a continuous tone. Operates from 9V battery (not included). Size of board: 1 1/4" x 1". Complete with all parts, PC board and instructions. Skill Level 1.