Friday, November 26, 2010
MI5 code name for the classified contract given to Marconi at Chelmsford in 1952 to determine how the listening device found inside the Great Seal presented to Ambassador Averell Harriman by the Soviets in 1944 really worked. The ingenious apparatus, designed by the NKVD’s Lev Thereman, with no discernable power source, had baffled the Federal Bureau of Investigation’s scientists, but a young British technician, Peter Wright, grasped the principles of passive cavity resonance and succeeded in demonstrating how the human voice’s sound waves vibrated a sensitive filament which, when bombarded with microwaves at 330 MHz, moved at a frequency that could be picked up by a remote radio receiver. A sensitive diaphragm contained in a brilliantly engineered cylinder attached to a short antenna acted as a microphone and transmitter when activated by the microwave beam. The device was intended to have an unlimited life, picking up all the conversations conducted in the ambassador’s study at his residence, Spaso House. On the strength of this accomplishment, Wright was offered a permanent position in the Security Service as a technical adviser.