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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.
Would it have been possible for the speakers of the time to emit those frequencies? Imagining the equivalent of a Twitch raid: "I'm done broadcasting so I'm going to send you to the next channel."
We had a TV that used ultrasonic sound to control the TV, When I was young I could fairly hear the tone from a couple of the buttons, though super faintly, but the dog would cock its head when certain buttons were used.