ADM-3A Lear Siegler terminal
Photograph by Konrado Fedorczyko, 2004

Nicknamed the 'dumb terminal', the ADM-3A, was a popular video display terminal introduced by Lear Siegler in 1976. It played a significant role in the early days of personal computing, widely used in the late 1970s and early 1980s. Featuring a 12-inch monochrome CRT display capable of showing 12 lines of 80 characters each, it boasted a built-in ASCII keyboard with 59 keys, including alphanumeric keys, function keys, and control keys, and typically utilised a serial interface (RS-232) for communication with host computers. Supporting the ASCII character set, it offered a resolution of 72 columns by 20 rows of text and various control codes for cursor positioning, screen clearing, and other display functions. Widely adopted for early microcomputers and minicomputers, it found popularity among hobbyists, programmers, and businesses for tasks like word processing, data entry, and remote system access. Its compact, rugged design made it suitable for office and industrial environments, and despite being introduced in the mid-1970s, it remained in use for years, becoming an iconic terminal in computing history and influencing subsequent video display terminal designs and early user interface standards.


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