Researcher has developed, at a cost of less than one dollar, a wireless light switch that runs without batteries, can be installed anywhere on a wall and could reduce the cost of wiring a house by …::A U of A engineering researcher has developed a wireless light switch that could reduce the cost of wiring a house by as much as 50 per cent.

    • henchman2019@lemmy.world
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      11 months ago

      Those worked by sound. No power was needed or generated by the remote.

      From the article…

      By pressing a button on the remote, you set off a spring-loaded hammer that strikes a solid aluminum rod in the device, which then rings out at an ultrasonic frequency.

      I THINK I even remember, way back, random channel changes from tapping on a drinking glass or something similar… Cool tech for the time