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The buttons on Zenith’s original “clicker” remote were a mechanical marvel
(www.theverge.com)
This is a most excellent place for technology news and articles.
Interesting purely mechanical design. Our first remote (that didn't have a cable connection) used sound as well, but it was battery powered and as a kid, I could hear at least some of those sounds. It had way more than just 4 buttons though, maybe the mechanical design hits a limit there at some point (or electronics just got cheaper).