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 emits a high pitched irritating alarm tone! When they turn the light on again to look for the culprit it keeps silent! Easy to build and loads of fun to use.

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Complete with all parts, PC board and instructions. Skill Level 1.Size of board: 2.9” x 1.8”.Operates from one 9V battery (not included).