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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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