VT420
| Industry | Computer hardware |
|---|---|
| Founded | November 7, 1957 |
| Fate | Acquired by Compaq (1998) |
| Headquarters | Maynard, Massachusetts , United States |
| Products | Computer terminals, computers, software |
The VT420 is a computer terminal adhering to the ANSI standard, launched in 1990 by Digital Equipment Corporation (DEC). It represents the only model within the 400 series, taking over from the VT320. No terminals with color or graphics capabilities were produced in this series; users needing ReGIS and Sixel graphics along with color functionality continued to use the VT340. The VT420 and the VT300 series were eventually replaced by the less prominent VT500 series beginning in 1993.
Description
Building upon the VT320, the VT420 introduced enhanced features including multi-session functionality initially available on the VT330 and VT340 models.
These terminals incorporate a technology called TD/SMP, which allows two sessions to be combined over a single serial link connected to a compatible terminal server, or alternatively managed through multiple MMJ ports using separate serial lines. The VT330, VT340, and VT420 support switching between sessions as well as displaying them simultaneously in either horizontal or vertical split-screen modes.
Additional enhancements encompass various PC character sets designed to facilitate numerous PC applications, alongside commands for editing rectangular screen areas—such as filling or clearing selected regions—supplementing the terminal-side editing capabilities introduced with the VT300 series.
The VT420 accommodates five distinct sets of 94 characters for standard usage, three sets comprising 128 PC characters, and one set containing 96 symbols for graphics and mathematics. It also permits uploading customized character sets through the Sixel protocol. The terminal supports the National Replacement Character Set, enabling substitution of characters (for example, swapping with ) to suit regional language requirements.
Consistent with all DEC terminals released after the VT100, the VT420 provides emulation modes for previous models including both VT100 and VT52.
Equipped with a 14" flat CRT display, it offers an 800×400 pixel resolution capable of showing either 80 or 132 characters per line and supporting 24, 36, or 48 lines vertically. Although typically displaying 25 lines at standard font size, the final line is commonly reserved for status indicators such as . The MMJ interfaces allow data transfer rates up to 38,400 bits per second, doubling the maximum speed available in earlier VT300 series terminals.
References
- Installing and Using the VT420 Video Terminal, DEC, 1990
- VT420 Programmer Reference Manual, DEC, 1992