VT525
| Industry | Computer hardware |
|---|---|
| Founded | November 7, 1957 in Maynard, Massachusetts, United States |
| Defunct | June 26, 1998 |
| Fate | Acquired by Compaq |
| Headquarters | Maynard , United States |
| Products | VT520 terminal, VT500 series terminals |
The VT520 is a computer terminal adhering to the ANSI standard, launched by Digital Equipment Corporation (DEC) during 1993–1994. This model is a monochrome, text-only terminal capable of handling multiple sessions simultaneously and includes an integrated 14" display. In contrast, the VT510 was designed for single-session use, while the VT525 incorporated color capabilities and required an external monitor.
Replacing all prior models in DEC's VT lineup—such as the VT420 text terminal and the VT340 graphics terminal—the VT500 series was introduced in response to growing competition from affordable IBM PC clones running terminal emulation software. These terminals represented DEC’s more economical and simplified option. After selling its terminal business in August 1995, DEC ceased production of the VT series, which had reached sales of approximately six million units.
Following DEC’s exit, the VT520 continued to be offered by Boundless Technologies until that company ceased operations in 2003.
Description
By the mid-1990s, the availability of inexpensive personal computers priced below $1000, combined with terminal emulation programs, posed a significant challenge to dedicated terminals. To address this, DEC introduced the VT500 series as streamlined and budget-friendly alternatives to the VT420 and VT340 models. These terminals featured text-only screens and added connectivity options including an RS-232C serial port, a Centronics port, and a PS/2 keyboard interface for easier integration into existing setups. Additionally, they maintained two proprietary MMJ serial connectors and keyboard ports unique to DEC.
The VT510, released in 1993, was an integrated unit with a built-in 14" screen; the VT520 supported up to four concurrent sessions using TD/SMP (referred to as SSU on terminals). The color-capable VT525 came in a slim "pizza-box" chassis equipped with an SVGA port for connecting an external monitor.
All models within the VT500 line functioned as ANSI-compliant terminals. While the VT510 allowed only one session at a time, both the VT520 and VT525 could manage up to four simultaneous sessions—doubling the capacity of earlier models. Users had the option to toggle between sessions using keyboard shortcuts or divide the display horizontally or vertically to view multiple sessions concurrently. The terminals included multiple character sets stored in ROM encompassing DEC-specific, international, and PC character sets. They also supported custom characters through sixel graphics and allowed single-character substitutions utilizing the National Replacement Character Set—for example, replacing "$" with "£" for UK keyboard layouts.
Serial communication speeds were enhanced to 115.2 kbps from the previous 38.4 kbps found on VT300 series devices; any serial port could accommodate two sessions via TD/SMP technology. These terminals emulated legacy systems such as the VT100 and VT52, along with others like Wyse, ADDS, and TeleVideo models. In addition to ANSI color commands, they supported custom escape sequences inherited from earlier VT terminals.
A novel feature was the inclusion of built-in desk accessories operated by the terminal’s CPU—these included a calculator, alarm clock, calendar, and character set viewer.
In terminal emulation software specifications, "VT500" often collectively denotes compatibility with all three models: VT510, VT520, and VT525.