DECwriter
| Industry | Computer hardware |
|---|---|
| Founded | May 16, 1957 |
| Headquarters | Maynard, Massachusetts , United States |
| Products | DECwriter series (computer terminals and printers) |
The DECwriter lineup consisted of a series of computer terminals developed by Digital Equipment Corporation (DEC), primarily functioning similarly to a teletype, where computer output was printed on paper and input was entered via a keyboard. In contrast to teletypes, DECwriters utilized early dot matrix printer technology. Models without keyboards served exclusively as computer printers and were later rebranded as DECprinters when smart terminals became widespread in the 1980s for interfacing with mainframe and minicomputer systems.
This family comprised four principal models: the initial DECwriter introduced in 1970, followed by the DECwriter II in 1974, DECwriter III in 1978, and DECwriter IV in 1982. The first three models were sizable units mounted on stands that used fanfold paper, with differences mainly in speed and connectivity options. The DECwriter IV was designed as a compact desktop device, visually similar to an IBM Selectric typewriter. Most versions were available in print-only configurations lacking keyboards. Notably, the II and III series ranked among DEC’s top-selling products.
DECwriter
Debuting at the Fall Joint Computer Conference in November 1970, the original DECwriter (model LA30) was among the earliest dot matrix printers, closely following the Centronics 101. It aimed to replace conventional teletypes such as the ASR-33 but did not support punched tape functionality. The LA30 featured a single interface: a 30 mA current loop, a standard connection for teletype devices, intended as a substitute for Teletype Models 33, 35, and 37 KSR.
The LA30 utilized a 64-character ASCII set limited to uppercase letters, printed by means of a 7-pin print head forming characters on a 5x7 dot matrix. It produced 80-column lines on standard -inch tractor-fed paper at speeds up to 30 characters per second (cps), matching its interface rate of 300 bit/s. Additionally, it supported slower transmission rates of 110 and 150 bit/s. Carriage return operations required pauses lasting approximately one second, during which the host system needed to transmit "fill characters."
The physical dimensions measured , with legs elevating the keyboard to desk height and an overall height of . Paper was fed upward from beneath through an opening in the stand. Its keyboard casing had a curved design reminiscent of the ADM-3A; the front panel could be lifted for maintenance tasks and paper loading. DEC recommended maintaining at least clearance behind the unit for full accessibility.
In June 1972, two new variants were launched: the LA30A, which functioned as a printer-only model without a keyboard, and the LA30-E, which added an RS-232 interface (with "E" denoting EIA-232 compatibility). Subsequently, the LA30-P model incorporated a parallel Centronics port, which had become widely adopted as a standard interface by the mid-1970s.
DECwriter II
Introduced in August 1974, the DECwriter II series succeeded the original model with its first release designated as the LA36. Retaining much of the LA30’s printing mechanism, the LA36 featured a smaller, more rectangular form factor. Similar to its predecessor, it was also offered as a keyboard-less printer-only version under the name LA35.
A significant advancement was the integration of a data buffer that allowed continuous data reception from host computers even while printing delays such as carriage returns occurred. This innovation enabled print speeds reaching up to 60 cps and simplified interfacing by removing the requirement for fill characters, thereby reducing device driver complexity.
Additional improvements included support for the complete 128-character ASCII range with both upper and lower case letters plus control characters stored in read only memory (ROM). Optional ROM modules provided extended character sets including Katakana and APL symbols. The keyboard featured 63 keys conforming to ANSI X4.14-1971 standards along with an extra set of 19 keys dedicated to numeric input and control functions. The tractor feed mechanism was adjustable for paper widths ranging from , supporting up to 132 columns per line. The print head could impress through six layers of paper, facilitating use with carbon paper or carbonless forms.
The widespread adoption of DECwriter II encouraged third-party enhancements that expanded its capabilities. For example, Intertec’s Superdec card provided support for 1200 bit/s data rates, double-width characters, APL symbols, and customizable character sets. The Datasouth DS120 enabled bidirectional printing without additional character sets. Meanwhile, Selanar’s Graphics II board introduced support for bitmapped graphics and increased communication speeds up to 9,600 bit/s.
DECprinter I and updated DECwriter IIs
The DECprinter I (model LA180) was introduced in September 1976 as a streamlined version of the LA35, equipped solely with a Centronics interface and capable of speeds up to 180 characters per second. By November, the LA35 and LA36 models received upgrades incorporating serial ports to facilitate easier integration with DEC systems, quickly becoming some of DEC’s most popular offerings.
DECwriter III
In January 1977, the DECwriter III (LS120) was unveiled as a cost-effective enhancement of the LA36, supporting only serial input. November 1978 brought three variants based on the LS120: the print-only LA120-RA DECprinter III, the terminal replacement model LA120-DA, and the LA120-RB which featured improved capacity for thick-copy paper.
While mechanically akin to earlier models, the LA120 incorporated a 1 kB character buffer allowing entire lines to be stored and enabling bidirectional printing techniques that raised throughput to 180 characters per second. It broadened character set options by including National Replacement Character Sets for multiple European languages, along with eight selectable character widths and double-strike bold functionality.
Alongside the standard RS-232 interface, optional add-ons were available: current loop (LA12X-AL), parallel port (LA12X-BB), Unibus interface (LA12X-CB), and an expanded 4 kB buffer module (LA12X-DL).
DECwriter IV
June 1982 marked a complete redesign with the introduction of the DECwriter IV, transitioning from bulky floor-standing devices to compact desktop units resembling electric typewriters such as the IBM Selectric. Operating at 30 characters per second, these printers were intended for different applications than the faster III series.
Two configurations were offered: the LA34 featuring a roller feed similar to typewriters, and the LA38 which added a tractor feed mechanism (also sold separately for use with the LA34). Both models fed paper from above, removing any space beneath for paper handling. The friction feed on the LA34 proved less dependable for unattended high-volume printing compared to the tractor-fed LA38.
The IV series also introduced optional compatibility with DEC’s sixel graphics format, enabling monochrome graphic output by controlling six print head pins through six data bits. This approach allowed efficient transmission of graphics over 7-bit communication links along with horizontal data scaling at varying characters-per-inch rates.
Letterwriter 100
The LA100, closely related to the IV series, utilized a nine-pin print head supporting three print speeds that corresponded to draft, memo, or letter-quality modes. Draft mode reached speeds of 240 characters per second, while letter quality employed a 33 by 18 dot matrix at 30 characters per second. The device was offered as either the print-only Letterprinter 100 or various Letterwriter 100 terminal configurations.
Its internal character ROM included support for British, Finnish, French, Canadian French, German, Italian, Norwegian/Danish, Spanish, and Swedish character sets. Furthermore, plug-in ROM cartridges containing glyph data enabled simultaneous use of up to five different character sets through two cartridges combined with three internal ROMs.
DECwriter Correspondent
The compact and portable LA12 DECwriter Correspondent weighed approximately , featuring built-in modems or alternative interfaces depending on the model. It shared many characteristics and functionalities with the DECwriter IV series.