VT520
| Industry | Computer hardware |
|---|---|
| Founded | November 8, 1957 |
| Defunct | June 26, 1998 |
| Fate | Acquired by Compaq |
| Products | VT520 computer terminal, VT510, VT525, VT420, VT340 |
The VT520 is a computer terminal adhering to the ANSI standard, introduced by Digital Equipment Corporation (DEC) during 1993–1994. This model is a monochrome, text-only terminal capable of handling multiple sessions simultaneously, featuring an integrated 14-inch display. Its counterpart, the VT510, supported only a single session, whereas the VT525 offered color capabilities and connected to an external monitor.
Replacing DEC's earlier VT series, which included the VT420 text terminal and the VT340 graphics terminal, the VT500 series was launched amid intensifying competition from affordable IBM PC clones running terminal emulation software. These models were designed as streamlined, budget-friendly alternatives. DEC divested its terminal business in August 1995, concluding the VT line after selling roughly six million units.
Following this, the VT520 continued to be available through Boundless Technologies until that company ceased operations in 2003.
Description
During the mid-1990s, the decline in terminal demand was driven by decreasing PC prices—falling below $1000—and the increasing use of terminal emulators. In response, DEC introduced the VT500 series as economical successors to the VT420 and VT340 models. These terminals were text-only and incorporated RS-232C serial ports and Centronics interfaces, along with a PS/2 keyboard connector to facilitate easier system integration. They also retained two proprietary DEC MMJ serial ports and keyboard connections.
Launched in 1993, the VT510 featured a compact all-in-one design with an integrated 14-inch screen. The VT520 expanded functionality by supporting up to four simultaneous sessions through TD/SMP (referred to as SSU on these terminals). The VT525 further enhanced features by adding color support and adopting a pizza box chassis with an SVGA port for connecting an external monitor.
All models within the VT500 range primarily operated as ANSI-compliant terminals. While the VT510 allowed for a single session, both the VT520 and VT525 could manage up to four concurrent sessions—doubling the capacity of earlier models. Users had the option to switch between sessions using keyboard shortcuts or to divide the display horizontally or vertically for simultaneous multi-session viewing. The terminals housed multiple character sets in ROM, including DEC’s own sets, international variants, and PC character sets. Additionally, users could load custom characters or substitute individual symbols—for example, replacing the dollar sign with a pound sign on UK keyboards.
Serial communication speeds were enhanced from previous models’ 38.4 kbps up to 115.2 kbps. Each serial port was capable of managing two sessions via TD/SMP. The terminals provided emulation for legacy devices such as the VT100 and VT52, as well as various other manufacturers’ terminals like Wyse, ADDS, and TeleVideo. Support included ANSI color commands alongside traditional escape sequences found in earlier VT models.
A significant feature was the inclusion of built-in desk accessories that operated on the terminal’s CPU; these tools comprised a calculator, alarm clock, calendar, and a character set viewer.
In documentation for terminal emulators, compatibility is often indicated by referencing the entire VT500 series collectively rather than specifying individual models such as the VT510, VT520, or VT525.