From Ed Prior
You report that, for security reasons, the Kremlin is thinking of using typewriters instead of computers (20 July, p 19). Ironically, in the 1970s, the Soviets developed a highly sensitive optical instrument that they used to monitor the vibrations of certain windows in Washington DC. As secretaries typed government memos, each key struck caused a slightly different vibration, allowing the Soviets to eavesdrop on the content of those memos.
After the US discovered this was going on, someone invented silent typewriters. Perhaps the Kremlin ought to review some of the old files on this technology.
Poquoson, Virginia, US
