Digital VT05 and VT420 (1970 and 1990)

The video terminal is the unsung hero of the computing world. Often toiling aware in warehouse, factories, colleges, shops and other places out of the public eye, the video terminal was a dependable workhorse for decades… well into the era of the PC.

Arguably the king of the terminal market was Digital Equipment Corporation (“DEC” or just “Digital”) who made terminals that were attached to minicomputers or mainframes, where they could run a wide variety of centralised applications that typically ran on Unix or VMS boxes.

They comprised of not much more than a display, keyboard and serial interface – and although they were not always cheap to buy, they were certainly cheap to run with no moving parts and complete immunity to computer viruses and other malfeasance. You could plug one in and forget about it for years, and it would keep doing its job.

DEC VT05

The DEC VT05 was introduced in 1970 and was Digital’s first standalone raster video terminal. Sure, I could tell you that it was a bit of an upgrade from the glass teletype concept with a bit of cursor control thrown in but probably the thing about the VT05 that most people will notice is how it looks. Digital’s radical space-age design made it look like the terminal was leaping out of the work surface. Inside the system boards were slanted behind the CRT rather than subsequent models which were more conventional inside. It looked fantastic, but the downside was that the VT05 was 30 inches (76 centimetres) deep which meant that you’d likely have to re-engineer your working environment to put one in. At 55 pounds (25 kilograms) it was hardly a lightweight device, so you wouldn’t want to move it anyway.

It could only display uppercase characters, but the keyboard could enter both upper and lowercase. Quite how you were meant to tell what you were typing is a mystery. Maximum data transfer rate was 2400 baud. The VT05 had a video input so you could display other things on the monitor, and mix them together with the text. The VT05 was around for five years until the much more capable – and conventional – VT52 was launched.

DEC VT420

Fast forward twenty years and the direct descendant of the VT05 – the VT420 – is launched. Don’t expect two decade of development to count for all that much though, the VT420 was still conceptually the same thing. Unlike the VT05, the VT420 was a practical design with a separate keyboard and a monitor on a tilt-and-swivel stand that was supplied as standard (unlike previous versions). It weighed just 8kg so wasn’t a problem to move about a bit, and the ANSI character set that it supported allowed full cursor addressability and enough predefined graphics to make a nice user interface.

The VT420 also supported dual sessions, typically by using the two serial ports on the back. Not only could you interact with two utterly different systems, but you could also copy-and-paste between them. That might not seem like a big deal now, but back in 1990 most people still couldn’t paste data between applications on their PCs so it was kind of a big deal.

The data transfer rate was a speedy 38,400 baud using the compact phone-like MMJ sockets, the screen had a maximum capacity of 132 x 48 lines of text and the latest revision of DEC’s legendary keyboard – the LK401 – was almost perfect in every way except for the annoying lack of an Escape key.

Where the VT05 marked a point near the beginning of DEC’s journey, the VT420 marked a point near the end. The days of centralised minicomputers were starting to fade and throughout the 1990s PCs and Macs became more capable professional computing environments. The VT420 was a success but it lasted just three years before being replaced by the VT520 which was almost identical. DEC sold the entire terminal division in 1995 and they themselves were taken over by Compaq in 1998, who were then taken over by HP in 2002.

The VT range soldiered on with Boundless Technologies until 2003, and other manufacturers either closed down or shuttered production in the following years, including Wyse and Qume until there were none left.

Even though the manufacturing of terminals dried up, the computer systems that relied on them still exist. VT terminals are still in use around the world, but newer installations will typically rely on a PC with some terminal emulation software – a more complex and less reliable solution.

Today a DEC VT420 in good condition second-hand can cost a couple of hundred pounds, and maybe budget a thousand or so if you want to acquire a VT05. Of course terminal emulators can be had for less, a client such as PuTTY is free or Reflection is a more commercial offering.

Image credits:
Matthew Ratzloff via Flickr – CC BY-NC-ND 2.0
Adamantios via Wikimedia Commons – CC BY-SA 3.0

Digital (DEC) VT100 (1978)

DEC VT100

Launched August 1978

Although the late 1970s saw the birth of the microcomputer revolution, most people in businesses and academia still used a big mainframe computer or minicomputer (such as a DEC VAX) connected to a dumb terminal, for example the DEC VT52 or Lear-Siegler ADM3A.

Early terminals were nothing more than glass teletypes – essentially replacing a box of fanfold paper with a screen. The next big advance was to make the cursor addressable, in other words to be able to place text wherever you wanted on the screen. And it was the VT52 (launched in 1975) which introduced a lot of these features to customers for the first time.

The Digital Equipment Corporation (known as DEC or just Digital for short) wanted to develop the dumb terminal further, and in August 1978 they launched the DEC VT100 which pushed the boundaries ever further with support for ANSI X3.64 codes which pretty much allowed you to do anything you liked text-wise, plus it came with some rudimentary block graphics which were very handy for designing on-screen forms.

This was sophisticated stuff for the late 1970s, and the key breakthrough here was the use of an Intel 8080 (or later the 8085) microprocessor to do the hard work. Depending on variant, the 12” display could show 80 x 24 characters or up to 132 x 24 characters for a top-of-the-range version. The relatively fast 19200 baud serial interface was enough to display a full screen of 80 column text in just a second. And unlike many earlier terminals, the keyboard was attached to the main unit with a curly cable, so you could move it about to whatever position you found comfortable.

As with the VT52, the VT100 came in quite a big case which could allow extra boards to be added, turning the platform into a graphics terminal (with the VT125) or even a full-blown microcomputer with the VT180. Printers could even be attached to the back of the terminal, so you could easily have your own printer rather than sharing with the rest of the office.

The V100 family was a significant success at the time, and it and its successors sold six million units worldwide, until finally going out of production in 2017 with the VT520. One of the reasons that the VT terminal survived so long against more capable PCs was the low running cost – there was very little to go wrong, no moving parts and VT terminals were immune to things like computer viruses. VT terminals are still in use worldwide in locations where these things are important, such as warehouses.

But perhaps more commonly these days, pretty much any terminal program emulates a VT100 by default, including the command line interface on Macs and Linux systems. Perhaps more importantly, the VT100 paved the way for modern computer applications. Connecting one to a modern computer system is a bit tricky as VT terminals primarily use a serial interface, but if you get your hands on a terminal server or media converter you might be able to make it run on Ethernet, if you are up for the challenge..

Image credit: Wolfgang Stief via Flickr

Lear Siegler ADM-3A (1976)

Lear Siegler ADM-3A

Announced July 1976

Once upon a time, there was a California company that produced a radically designed and rather beautiful device that transformed the way people dealt with technology. Over the years, this particular product gained a cult following that took on an almost religious fervour. You might be forgiven for thinking that this company was Apple, but it wasn’t. Instead this company was called Lear Siegler International (LSI), the year was 1976 and the product was the ADM-3A.

The ADM-3A was a dumb terminal, similar in concept to the DEC VT52 launched the previous year, and following on from the almost identical looking ADM-3 also from 1975. A simple device comprising pretty much of just a keyboard, screen and communications ports, it would plug into a contemporary computer which could range from a multi million dollar mainframe to a hobbyist microcomputer costing a few hundred dollars. The ADM-3A was much more usable than the ADM-3 though, supporting both upper and lowercase characters and having a cursor-addressable screen (like the VT52), both features the ADM-3 lacked.

Two things made the ADM-3A stand out. The first was the relatively low price of $1045.. which although equivalent to about a whopping $5500 today (much more than a top-of-the-range iMac) was actually a fair bit cheaper than the competition.

But perhaps the main thing that made it stand out was the design. Most terminals of the time were boxy affairs, but the ADM-3A curved instead. A clamshell design with a hinge in the back, the ADM-3A’s lines followed the shape of the CRT, swooping down to the base where the mainboard was installed. The curves were echoed almost everywhere, on the front, around the CRT and on the base. In fact, the only real appearance of straight lines was at the front where the keyboard was.

Lear Siegler could also produce the ADM-3A in different colours, which was a simple process of changing the plastics used in the moulding. But hang on... curves, different colours... doesn’t that sound a bit like the original Apple iMac G3? There are certainly some interesting parallels there.

The price of the ADM-3A steadily dropped, hitting just $595 in 1981 (equivalent to about $2000 today), shipping 150,000 by that point. Those were huge numbers of the time, and ADM-3As could be found hooked up to mainframes, Unix systems and even rudimentary home computers. Helping to introduce computing to the masses? That does sound a bit like another California corporation, doesn’t it?
 

Now, you might be wondering about the “Lear” name in the company. Lear Siegler was founded by the merger of two companies, one of which was Lear Avionics founded by William “Bill” Lear*. Lear later went on to build executive jets that still bear the “LearJet” name today, although he sold his interest in Lear Siegler in 1962. LSI still exists today, although simply called the Lear Corporation, and it employees 136,000 people… which is more than Apple does.

But there’s another parallel between Lear Siegler and Apple – the ADM-3A was launched at the same time as the original Apple I, Apple’s first commercial product. Coincidentally, the Zilog Z80 microprocessor was also announced in July 1976. All-in-all, it was a pretty good month for landmark technologies.

You can still buy a used ADM-3A today, although most of the available ones seem to be in the US with prices at typically $400 to $500. And in case you don’t know what you would do with one, one particular mad genius interfaced one with a Raspberry Pi. Oh yes... as for cult there was a Usenet newsgroup called alt.religion.adm3a in the 80s and 90s, presumably created for followers of the One True Terminal.

* Lear invented the first car radio for Motorola, created the 8-track tape and pioneered business jets plus a whole lot of other stuff. He was a very clever guy. Eventually the LearJet corporation ended up as part of the giant Bombardier group, but the Lear name still lives on in the Lear Corporation which has a history of the company here.

Image credits [1] [2]

DEC VT52 (1975)

Launched September 1975

Think of the exciting end of today’s technological spectrum. You might come up with smartwatches, 4K TV and internet-connected fridges. Now think of the other end. Perhaps you might think about UPS maintenance, Sarbanes-Oxley compliance and replacing the pickup rollers in your laser printer. Well, I am going to talk about computer terminals which most people will think belongs on the less-sexy end of the scale..

..but wait. Go back forty years to September 1975. If you were a grown-up back then, you might be lusting after one of those new-fangled digital watches. But it you were very lucky, then perhaps your employer would buy you something like a Digital Equipment Corporation (DEC) VT52 instead.

If you belong to the generation that puzzles over why the icon for “save” is a floppy disk but you have never seen one, then perhaps an explanation is in order. A computer terminal is a pretty simple device that connects to a bigger computer with many users, sometimes in the same building, sometimes thousands of miles away. Back in the mid-1970s, this sort of thing was the state-of-the-art. That computer would sometimes be somewhere else in the same building, or it could be hundreds or thousands of miles away. To some extent, a terminal was just the ultimate thin client.

When the VT52 was launched in September 1975, it marked a significant transition from really incredibly dumb teletypes to devices that could run something that looked rather more like a modern business application. In other words, it helped to take computing out of the realms of the geeks and put it on people’s desks in the office instead.

OK. If you are of the iPad generation then perhaps your eyes are glazing over, but before the 1970s, the most user-friendly way you could interact with a computer was by using a teletype - basically a printer with a keyboard and a computer interface on the back. Everything you typed got printed out, and every response from the computer was printed out too. These things were connected to a box of 2500 sheets of fanfold paper which would run out from time-to-time. And they were noisy. And they were slow.

Sometime in the late 1960s, somebody had the really good idea of replacing the paper with a cathode ray tube, but although they were quieter and eliminated a lot of dead trees, they were still massively dumb devices. These were called glass teletypes, and essentially they worked in the same way as paper-based ones.

But come the 1970s, not only did we have the Bay City Rollers, but also these horribly dumb devices were becoming just a bit more intelligent, which leads us to the DEC VT52. A product of the Digital Equipment Corporation (aka “Digital” or “DEC”) of Massachusetts, the VT52 and its competitors offered some revolutionary features that would help to define modern computing.

Where a glass teletype simply printed out what it received, a terminal such as the VT52 could do a lot more. The single biggest advance was that the computer could move the cursor around the screen and output whatever it wanted, wherever it wanted. And the more basic things like being able to support both uppercase and lowercase characters at the same time certainly helped.

What this all meant was the computers suddenly became much more interactive. Instead of typing something in and just getting a response, you could create forms for entering data. Or create a spreadsheet. Or edit documents. It was the VT52 and its contemporaries that helped to build recognisably modern applications. Perhaps more importantly of all, it opened the way to quite sophisticated games such as DECWAR and Rogue.

The VT52 itself came in several different versions, including one with a printer that could dump the contents of the screen onto a wet sheet of paper. Lovely. And one key design flaw with the VT52 turned out to be the relatively flat top which ended up being covered with papers and manuals.. which lead to overheating.

Typically paired with a DEC PDP-11 minicomputer, the V52 was widely adapted by other computer systems too. In 1978 the VT52 was replaced by the DEC VT100, which became the standard terminal to emulate even today. DEC was taken over by Compaq in 1998, which itself was taken over by HP in 2002. But the direct descendant of the VT52, the VT520, is still in production today.

Within a few years microcomputers such as the Apple II and Commodore PET had moved the computer away from the control of the IT department and fully onto the user's desk, and for a long time it seemed that "thin clients" would vanish. However, the emergence of the World-Wide Web in the 1990s swung the technology the other way.

These days, 1970s DEC terminals in good condition can sell for hundreds of dollars to collectors, despite being about as useful in modern computing as a chocolate teapot.

Image credits [1] [2]