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The VT520 is an ANSI standard
computer terminal A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and ...
introduced by
Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president un ...
(DEC) in 1993 and 1994. The VT520 is a multi-session monochrome text-only terminal with a built-in 14" monitor. The VT510 was a single-session version, while the VT525 added color support and used a separate external monitor. The VT500s replaced all existing models of DEC's VT line, which at that time consisted of just the VT420 text and VT340 graphics terminals. It was introduced in an era when the market was being flooded by low-cost
IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard. Released on August 12, 1981, it was created by a team ...
clones which could perform the same functions using a
terminal emulator A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term ''terminal'' covers all remote term ...
while also running other software. DEC introduced the VT500s only a short time before selling off their entire terminal division in August 1995. This brought the VT series to a close, after a total of about six million terminals had been sold. The VT520 was available from Boundless Technologies until the company went defunct in 2003.


Description

By the mid-1990s the price of low-end PCs was rapidly falling to under $1000. When equipped with a
terminal emulator A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term ''terminal'' covers all remote term ...
, these machines could perform all the functions of a DEC terminal, as well as running software locally. The terminal market began to crash, but remained important to DEC's core
minicomputer A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ' ...
business. DEC responded by introducing the VT500 series as simplified and lower-cost options to the existing VT420 and VT340. The new 500s were text-only but they added an
RS-232C In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' ('' data terminal equipment'') suc ...
serial port and a
Centronics port IEEE 1284 is a standard that defines bi-directional parallel communications between computers and other devices. It was originally developed in the 1970s by Centronics, and was widely known as the Centronics port, both before and after its IEEE ...
as well as a
PS/2 The Personal System/2 or PS/2 is IBM's second generation of personal computers. Released in 1987, it officially replaced the IBM PC, XT, AT, and PC Convertible in IBM's lineup. Many of the PS/2's innovations, such as the 16550 UART (serial po ...
keyboard connector which made them easier to integrate into a mixed computing environment. They also had two DEC proprietary MMJ serial connectors and a DEC proprietary keyboard port like their predecessors. The VT510 was introduced in 1993 as an all-in-one unit with a built-in 14" display. The VT520 was similar but supported up to 4 sessions using a system known as
TD/SMP TD/SMP, short for Terminal Device/Session Management Protocol, was a terminal multiplexer system introduced by DEC on their VT330/340 terminals in 1987. The terminal-side was referred to as SSU. TD/SMP allowed data from two separate host sessions ...
. The later VT525 color terminal dispensed with the integrated monitor as well, packaging the system into a pizza box case with an
SVGA Super VGA (SVGA) is a broad term that covers a wide range of computer display standards that extended IBM's VGA Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the I ...
port for connection to an external user-supplied monitor. Like all models of the VT series, the VT500's primary purpose is to act as an ANSI standard terminal. The VT510 supported only a single session, while the 520 and 525 supported up to four sessions, up from two in earlier VTs. The user can flip between the sessions using control sequences on the keyboard (typically ), or display multiple sessions at the same time by splitting the screen horizontally or vertically. All models have multiple
character set Character encoding is the process of assigning numbers to graphical characters, especially the written characters of human language, allowing them to be stored, transmitted, and transformed using digital computers. The numerical values that ...
s in
ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * R ...
, supporting DEC, international and PC characters. They can also replace any of these by downloading custom characters using
sixels Sixel, short for "six pixels", is a bitmap graphics format supported by terminals and printers from DEC. It consists of a pattern six pixels high and one wide, resulting in 64 possible patterns. Each possible pattern is assigned an ASCII chara ...
, and perform single-character swaps using the
National Replacement Character Set The National Replacement Character Set (NRCS) was a feature supported by later models of Digital's (DEC) computer terminal systems, starting with the VT200 series in 1983. NRCS allowed individual characters from one character set to be replaced b ...
, swapping with for use with UK keyboards for instance. The speed of the serial ports was increased to 115.2 kbps, up from 38.4 kbps on the VT300s. Any one of the serial ports could support two sessions using TD/SMP. Like earlier models of the VT line, the 500s could be put into modes emulating the
VT100 The VT100 is a video terminal, introduced in August 1978 by Digital Equipment Corporation (DEC). It was one of the first terminals to support ANSI escape codes for cursor control and other tasks, and added a number of extended codes for special f ...
and
VT52 The VT50 was a CRT-based computer terminal introduced by Digital Equipment Corporation (DEC) in July 1974. It provided a display with 12 rows and 80 columns of upper-case text, and used an expanded set of control characters and forward-only scro ...
, but added a wide variety of other emulations for
Wyse WYSE (970 AM) is a radio station located in Canton, North Carolina, that simulcasts WISE's sports format from Asheville, North Carolina. Owned by the Asheville Radio Group subsidiary of Saga Communications, the station is licensed by the Fede ...
,
ADDS Applied Digital Data Systems (ADDS) was a supplier of video display computer terminals, founded in 1969 by Leeam Lowin and William J. Catacosinos. Lowin simultaneously founded Solid State Data Sciences (SSDS). SSDS was one of the first developers ...
TeleVideo TeleVideo Corporation was a U.S. company that achieved its peak of success in the early 1980s producing computer terminals. TeleVideo was founded in 1975 by K. Philip Hwang, a Utah State University, Hanyang University graduate born in South Kore ...
and other terminals. The 500s also directly supported ANSI commands for color, like the Wyse, in addition to the custom
escape sequence In computer science, an escape sequence is a combination of characters that has a meaning other than the literal characters contained therein; it is marked by one or more preceding (and possibly terminating) characters. Examples * In C and man ...
s used for color support on previous VT models. Another new feature was the inclusion of a set of
desk accessories A desk accessory (DA) in computing is a small transient or auxiliary application that can be run concurrently in a desktop environment with any other application on the system. Early examples, such as Sidekick and Macintosh desk accessories, used s ...
running on the terminal's CPU. These included a calculator, alarm clock, calendar, and a character set viewer.
Terminal emulator A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term ''terminal'' covers all remote termin ...
specifications may refer to VT500 instead of VT510, VT520 and VT525 in the statements about their compatibility.


Notes


References


External links


Boundless Technologies support page
DEC computer terminals Character-oriented terminal Graphical terminals Computer-related introductions in 1994 {{compu-hardware-stub