"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. "
this post was submitted on 30 Jul 2023
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this is a space for Cassette Futurism -- retro images, media, design and technology from the 70s and 80s
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maybe still better than the flashlight/photocell types!