this post was submitted on 09 Sep 2026
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Privacy
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Speculating, but I would guess they applied a band pass filter to it. You can then either take a simple threshold value, or look for a rapid change and trigger off that. 4 buttons means 4 sets of filters, each tuned to a different frequency.
That said, the analogue electronics engineers of yesteryear were insanely competent and making analogue circuits do interesting things to save money or space.
Ah, yes, that makes sense, thanks! Totally agreed on those old school engineers being insanely competent and creative.
Randomly this appeared in my feed.
https://youtube.com/shorts/Qpyd7TsH14Y
Doesn't say anything about the receiver side, but shows the mechanism quite well.
Oh, awesome, thank you. Very interesting and very creative. No batteries!