Here is the SMD version of one of our all time best selling electronic kits. It operates the exact same way- Just set this kit in a 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 tone! When they turn on the light again to look for the culprit, it keeps silent again!

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Operates from 9V battery (not included). Size of board only 1 5/8" x 1 7/16". Complete with all parts, PC board and instructions. Skill Level 2.