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by InsomniacL
1367 days ago
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In 1945 the Soviet Union gifted a wall hung artwork to the USA embassy which passively transmitted audio signal from the room with no power supply or active electronics. https://en.wikipedia.org/wiki/The_Thing_(listening_device) in the last 77 years, I imagine this type and similar technology will be much more miniaturised and effective. |
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No internal power supply. Very important distinction.
"The device, a passive cavity resonator, became active only when a radio signal of the correct frequency was sent to the device from an external transmitter."
But the Thing was a transmitter. A receiver could be entirely passive and very small. It could easily fit in a dental implant. (There have been reports of people hearing AM radio broadcasts through their fillings.) But the risk of detection would be very high.