LittleAlex on Nostr: Early remotes for tellies was not using IR light or let alone Bluetooth as today. ...

Early remotes for tellies was not using IR light or let alone Bluetooth as today. Instead it was using sounds, usually above the hearing of people, a.k.a. ultrasound. The sounds was not created elecronically but with little metal cylinders hit by a little hammer when pushed a button, just like a xylophone. Each button was connected to it's own metal rod and the metal rods was tuned to it's own frequency.
A microphone in the telly received the sounds and separated the frequencies by the means of analogue filters. The according action like switching channel was also done by analogue circuits, nothing digital was used in consumer goods at this times.
For instance channel tuning was done with varicaps (https://en.wikipedia.org/wiki/Varicap) and the channel settings was stored in the position of potentiometres (https://en.wikipedia.org/wiki/Potentiometer) providing the voltage for the varicap.

#retrotech #oldtechnology #vintagetech