The buttons on Zenith's original clicker TV remote were a mechanical marvel - The Verge

(via Benji)

The “Zenith Space Command” (c. 1956) was one of the first wireless TV remotes. It had an ingenious design that used ultrasonic sound instead of light to change channels. By pressing a button, a spring-loaded hammer would strike an aluminum rod tuned to a specific frequency, with each button emitting a different high-frequency tone. Employing mechanical buttons, the remote required no batteries, and provided tactile feedback by way of a satisfying click, hence “clicker”!