Len Shustek writes: SAGE facts News of the Russian A-bomb in August 1949 created awaremess that we needed a system for information processing of air defense radar to detect attacks from over the north pole. Conventional radar detection plotted on manual boards was too slow to keep up with a enemy attack using supersonic bombers. SAGE (Semi-Automatic Ground Environment) was a huge computer installation designed to detect and track all aircraft, match against known friendly scheduled or military activity, and identify hostile tracks. It could then assign and guide manned interceptors or missles. Communications with ground and shipboard radar, weather stations, air traffic schedules, and other SAGEs were over phone lines, for which modems were invented. Operators used a "light gun" the way we use the mouse, in blue-lit dim rooms with built-in cigarette lighters and ashtrays in the console. Housed in windowless four-story blockhouses with blast- resistant walls.