Comment on 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 ...

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henchman2019@lemmy.world ⁨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.

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