IBM's Automatic Translator was a machine translation system that converted Russian documents into English. The Translator used an optical disk that stored 170,000 word-for-word and statement-for-statement translations and a custom computer to look them up at high speed. Built for the US Air Force's Foreign Technology Division, the AN/GSQ-16 (or XW-2), as it was known to the Air Force, was primarily used to convert Soviet technical documents for distribution to western scientists. The Translator was installed in 1959, dramatically upgraded in 1964, and was eventually replaced by a mainframe running SYSTRAN in 1970.