Coincidentally I happen to be reading a book on the same subject. From memory, how the commies picked up the signal was even more interesting. In a false chimne

Coincidentally I happen to be reading a book on the same subject. From memory, how the commies picked up the signal was even more interesting. In a false chimney attached to the Embassy they installed a remotely controlled Yagi antenna, that could be pointed at a particular target. At the top of the 'chimney' was a copper v-shaped dome serving to gather and focus the weak signal from the typewriters. The signal from the antenna was then sent through an amplifier and cable down a tunnel into the Soviet sector. The transmission from the typewriter consisted of a compressed burst-mode signal hidden in the side-bands of near-by television transmissions, making it virtually impossible to detect using normal bug detecting equipment. When the existence of such was reported to the ambassador, he said: can you bring us 100% proof the commies are bugging us.