3B series computers

The 3B series computers are a line of minicomputers made between the late 1970s and 1993 by AT&T Computer Systems' Western Electric subsidiary, for use with the company's UNIX operating system. The line primarily consists of the models 3B20, 3B5, 3B15, 3B2, and 3B4000. The series is notable for controlling a series of electronic switching systems for telecommunication, for general computing purposes, and for serving as the historical software porting base for commercial UNIX.