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Replica of the  Great Seal  which contained a Soviet bugging device, on display at the  NSA 's National Cryptologic Museum . 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 Soviets to the US Ambassador to Moscow on August 4, 1945. Because it was passive, being energized and activated by electromagnetic energy from an outside source, it is considered a predecessor of  RFID  technology. [1] Creation The Thing was designed by Soviet Russian inventor  Léon Theremin , [2]  whose best-known invention is the electronic musical instrument the  theremin . The principle used by The Thing, of a resonant cavity microphone, had been patented by Winfield R. Koch of the  Radio Corporation of America  (RCA) in 1941. In US patent 2,238,117 he describes ...

Replica of the  Great Seal  which contained a Soviet bugging device, on display at the  NSA 's National Cryptologic Museum . 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 Soviets to the US Ambassador to Moscow on August 4, 1945. Because it was passive, being energized and activated by electromagnetic energy from an outside source, it is considered a predecessor of  RFID  technology. [1] Creation The Thing was designed by Soviet Russian inventor  Léon Theremin , [2]  whose best-known invention is the electronic musical instrument the  theremin . The principle used by The Thing, of a resonant cavity microphone, had been patented by Winfield R. Koch of the  Radio Corporation of America  (RCA) in 1941. In US patent 2,238,117 he describes ...