See 14 FM Bugs to Build!
A 400m bug that picks up sounds through windows the the piezo element
shown. The feelers protruding from the center touch the window and pick up
vibrations and the Blu-Tac keeps it stuck to the window.
Includes 2 x AAA batteries and an ON/OFF slide switch. It will fit inside
a Tic-Tac box for presentation and protection.
Board dimensions: 1.9in x 0.55in.
3 Page article.