AN/GSA-51 Radar Course Directing Group

The Burroughs AN/GSA-51 Radar Course Directing Group was a United States Air Force air defense command, control, and coordination system, part of the Semi-Automatic Ground Environment system. It was intended to replace vacuum tube IBM AN/FSQ-7 Combat Direction Centrals. Developed under Electronic Systems Division's 416M Program, in 1962 Burroughs "won the contract to provide a military version of its D825" modular data processing system for the AN/GSA-51 to be used at "BUIC II radar sites" (follow-on to the initial Back-Up Interceptor Control System, BUIC) BUIC II was 1st used at North Truro Z-10 in 1966, and the Hamilton AFB BUIC II was installed in the former MCC building.

The first D825 computer was originally built for the Navy Research Laboratory with a designation of AN/GYK-3(V). The D825 contained between one and four 48 bit central processor/arithmetic units, up to 16 memory modules and up to 20 IO modules. The BUIC systems used "two computer modules, six memory modules and three input/output modules". The computer was designed for high availability and could still operate if any one of its modules failed.