Resonant cavity microphone – wanted item The Thing, also known as The Great Seal Bug, was a passive covert listening device, developed in the Soviet Union and planted in the residence of the US Ambassador in Moscow, hidden inside a wooden carving of the Great Seal of the United States. It is called a passive device as it does not have its own power source. Instead it is acivated by a strong electromagnetic signal from outside. The device was codenamed LOSS by the US and RAINDEER or DEER (ОЛЕНЬ) by the Soviets |