On
August 4, 1945, Soviet school children gave a carving of the
Great Seal of the United States to U.S. Ambassador Averell
Harriman. It hung in the ambassador’s Moscow residential
office until 1952 when the State Department discovered that
it was ‘bugged.’
The microphone hidden inside was passive and only activated when the Soviets wanted it to be. They shot radio waves from a van parked outside into the ambassador’s office and could then detect the changes of the microphone’s diaphragm inside the resonant cavity. When Soviets turned off the radio waves it was virtually impossible to detect the hidden ‘bug.’ The Soviets were able to eavesdrop on the U.S. ambassador’s conversations for six years.
The
replica on display in the museum was molded from the original
after it came to NSA for testing. The exhibit can be opened
to reveal a copy of the microphone and the resonant cavity
inside.