Set this kit in an inconspicuous place with light shining on it and it remains perfectly silent, however, as soon as the light is turned off the kit mits a high pitched irritating tone! When they turn the light on again to look for the culprit it keeps silent again! Easy to build and loads of fun to use. Operates from one 9V battery (not included). Size of board: 2.9" x 1.8". Complete with all parts, PC board and instructions.
Skill Level 1. This kit requires soldering of components to the PC board while building.