"""
"""
The Thing, also known as the Great Seal bug, was one of the first covert listening devices (or "bugs") to use passive techniques to transmit an audio signal. It was concealed inside a gift given by the Soviet Union to W. Averell Harriman, the United States Ambassador to the Soviet Union, on August 4, 1945. [...] it was passive, needing electromagnetic energy from an outside source to become energized and activate,
[...]
The Thing was designed by Soviet Russian inventor Léon Theremin, best-known for his invention of the theremin, an electronic musical instrument.
[...]
The Thing consisted of a tiny capacitive membrane connected to a small quarter-wavelength antenna; [...] a passive cavity resonator, became active only when a radio signal of the correct frequency was sent to the device from an external transmitter. [...] Sound waves [...] striking the membrane and causing it to vibrate. The movement of the membrane varied the capacitance "seen" by the antenna, which in turn modulated the radio waves that struck and were re-transmitted by the Thing. A receiver demodulated the signal so that sound picked up by the microphone could be heard, just as an ordinary radio receiver demodulates radio signals and outputs sound.
[...]
The existence of the bug was discovered accidentally by a British radio operator at the British embassy who overheard American conversations on an open radio channel as the Soviets were beaming radio waves at the ambassador's office. An American State Department employee was then able to reproduce the results using an untuned wideband receiver with a simple diode detector/demodulator, similar to some field strength meters.
[...]
surveillance counter-measures "sweep" of the Ambassador's office, using a signal generator and a receiver in a setup that generates audio feedback ("howl") if the sound from the room is transmitted on a given frequency. During this sweep, Bezjian found the device in the Great Seal carving.
[...]
the antenna and resonator had several resonant frequencies in addition to its main one, and the modulation was partially both amplitude modulated and frequency modulated.
"""
https://en.wikipedia.org/wiki/The_Thing_(listening_device)
https://en.wikipedia.org/wiki/The_Thing_(listening_device)

Labels: Oleg Zabluda

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