This is the wonderful clock beat amplifier we made a few years ago. It has been on the shelf since we moved. Tested, working great. For anyone working on clocks who has some hearing loss like I do, this is a great aid in hearing the action of the clock movement. Simply clamp the pick-up on, and listen.Requires a 9 volt battery and earphones.Measures 4 1/2 inches (with tabs) x 2 1/2 inches x 1 1/4 inches.