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In the April 1985 issue of Ahoy!, a reader asks whether it is possible to hook a conventional typewriter up to his Commodore 64. Surprisingly to me, columnist David Barron answers that such interfaces did exist in the recent past:

Years ago I remember devices that fit over a typewriter's keyboard and actually "pressed" the keys corresponding to signals from your computer. This was when letter quality printers were well over $1000 and beyond the reach of the hobbyist. Today, letter quality printers are available for a few hundred dollars, and daisy wheel typewriters with computer interfaces are available for a few dollars more.

I'm interested in learning more about these mechanical "devices that fit over a typewriter's keyboard and actually 'pressed' the keys". Were these commercially available, and if so, who manufactured them, what were they called, and what models of computer and typewriter did they work with? Are there any videos showing them in operation?

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    I never saw one at the time. My parents had a device that could connect to certain IBM typewriters electronically to turn them into printers for microcomputers.
    – JeremyP
    Nov 24, 2022 at 8:56
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    Yes, they existed, using selenoids, but they were all hacks, presented in magazines, not products, as far as I know of. No production I'be heared of.
    – Raffzahn
    Nov 24, 2022 at 10:40
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    @JeremyP There were several products to print to a Selectric; IBM themselves sold Selectrics with data storage, that could read from cards, and that could emulate a 2171 terminal. This is because the selectric internally used binary electric inputs to the type system. So effectively, the Selectric was already a printer, just one with a non-standard interface.
    – cjs
    Nov 25, 2022 at 22:41
  • @Raffzahn Well, some niche products existed. But as someone who had a computer in the early 1980s (Atari 400) as a teen, I don’t recall ever seeing one of these things. All I remember is there were letter quality printers — which were basically typewriters connected via some connections — but they were stand-alone printers and such. Nov 26, 2022 at 4:16
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    Reading the answers here makes you marvel at the robustness of electric typewriters at the end of that era. I used them: they would have taken this kind of abuse in stride. Today, our equivalent laser/ink-jet/other printers would quail in fear. Have you ever looked at the SLA of any modern printer you've just bought? The specified duty cycle in pages/month? Small office and especially home units have particularly and surprisingly low low low promises for how much you can use them. Exceed that (and the printer knows!) and your warranty is voidl 100WPM typing all day: bring it on!
    – davidbak
    Nov 27, 2022 at 18:37

6 Answers 6

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I remember such a device described in Personal Computer World magazine, June 1981: https://archive.org/details/PersonalComputerWorld1981-06/page/76/mode/2up?view=theater

The Dynatyper allows you to convert any electric typewriter into a printer for your micro. It is capable of thrashing your typewriter far faster than it was ever designed to be thrashed - 50 cps, in fact. You'll be pleased to hear that the accompanying software allows you to slow things down a little so that your machine doesn't fall to bits.

It seems like they drew the line at mechanical typewriters; I can't say I blame them.

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    Building a device to drive a mechanical typewriter would be very tricky business. I suspect it would need to be purpose-built for one specific model. You’d need to get the “throw” (distance traveled), force, and speed for pressing the keys just right. You’d need to mount the set of solenoids quite securely to the typewriter frame since it would be applying quite a bit of force to the keyboard. Then, what would you do about the carriage return lever? You’d need a solenoid-driven arm to move the carriage return lever.
    – Duncan C
    Nov 25, 2022 at 23:01
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    @DuncanC: If one wanted to design a device that could operate a mechanical typewriter, the best way to do it would be with a mechanism that was conceptually identical to that of an electric typewriter, using solenoids to cause the sides of plungers to hit a spinning roller. Without the economies of scale enjoyed by electric typewriter manufacturers, such a device would almost certainly be more expensive than the combined cost of a complete electric typerwiter and a set of solenoid actuators for it.
    – supercat
    Nov 26, 2022 at 7:44
  • @DuncanC electric typewriters didn’t need that much force. (More than a modern kb, but lots less than a mechanical typewriter.)
    – RonJohn
    Nov 27, 2022 at 13:53
  • @RonJohn my comment was about the practicality of building a driver for a mechanical typewriter. Agreed that the force to drive an electric typewriter would be less, but more than a computer keyboard. They were probably designed to be closer to the action of the mechanical typewriters they replaced.
    – Duncan C
    Nov 27, 2022 at 15:15
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Some further web searches on my part turned up a brochure for the I/O Pak Computer/Typewriter Mechanical Interface by Rochester Data Incorporated:

I/O Pak Brochure

The Rochester Data I/O Pak is an electro-mechanical device designed to interface between a conventional powered carriage return electric typewriter and any digital computer configured with a suitable electronic interface. The unit consists of a bank of specially designed solenoids mounted in an array that fits directly over the keyboard of the typewriter. Energizing a specific solenoid causes the respective typewriter key to be depressed, thus printing a character. Electrical actuation of the solenoid is accomplished by self contained drive electronics that operatein response to the selection of a pair of one-out-of-eight control lines.

The two models of the unit will operate virtually any electric typewriter that has powered function keys (carriage return, backspace, etc.) and a U.S. keyboard, with no mechanical modifications to the typewriter. All adjustments are self contained in the I/O Pak itself.

The unit features low profile, easy initial installation, instant detachability and replacement, modest power consumption and high reliability.

The brochure goes on to say that it is compatible with "all commercially available, powered carriage return typewriters". It has a general-purpose interface that is compatible with "almost any computer", as well as model-specific interfaces for the TRS-80 and Apple. A Commodore PET and industry-standard Centronics interface were under development. The company offered configuration software for the TRS-80 and Apple, plus a patched version of the Electric Pencil word processor. The entire kit (solenoid drive + computer interface + power supply) was available for just under $1000.

I couldn't find any videos of the I/O Pak in operation, but I did find this YouTube video of a homebrew device that operates in a similar manner:

https://www.youtube.com/watch?v=4_WfQoKRlxE

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  • Are/were keyboard sizes sufficiently standardized such that one size fits all?
    – dave
    Nov 25, 2022 at 15:34
  • The brochure implies that the size and layout of the keys is uniform; it's only the case that varies, and so the only physically adjustable parts of the interface unit are the mounting screws. The brochure also notes that typewriters may differ with respect to how fast they can be operated, so the interface's typing speed is software-configurable.
    – Psychonaut
    Nov 25, 2022 at 15:38
  • Especially on an IBM Selectric, an external device that interfaces through the keyboard is a bit of an overkill: The Selectric could actually be "computerized" with only a very small number of solenoids internally, because it used "mechanical binary coding" for the character selection.
    – tofro
    Nov 25, 2022 at 15:40
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    True, but as the I/O Pak brochure points out, the device travels well, can be installed in a few minutes, and doesn't require any internal or external modifications to the typewriter. So I can see the appeal for someone who travels with a computer. In the 1980s hotels catering to business travellers were likely to have typewriters, but not printers, for the use of guests.
    – Psychonaut
    Nov 25, 2022 at 16:02
  • That looks like exactly what the OP was asking about. (Voted). How did you manage to find that?
    – Duncan C
    Nov 25, 2022 at 23:02
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There was a commercially available interface to connect a TRS-80 to an IBM Selectric typewriter, the kind with the golf-ball type head. It wasn't a hack or a DIY recipe in a magazine, it was a commercial product. It wasn't a mechanical connection that struck the keys. The keyboard was still exposed, and I think you could still use the typewriter as a typewriter.

My father got one ca. 1980 and used it for many years in his solo law practice, in which he did all his own typing. The clerks at the courthouse kept complimenting him on what a perfect typist his "secretary" was. She never made a mistake! He used Michael Shrayer's Electric Pencil as his word processor. The early TRS-80's didn't have a shift key on the keyboard or the ability to display lowercase on the screen, but there was a kit you could buy to fix those things.

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  • This device? Maybe not, it appears to be 'solenoids on keys'.
    – dave
    Nov 24, 2022 at 21:20
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    I have one of these! (Selectric with serial interface.) I honestly don't know much about it -- I bought it on eBay a number of years ago, along with an IMSAI 8080. The IMSAI only sort of works, and I have never gotten around to trying to repair it; I've never even turned the Selectric on. I'm happy to take pictures of it or something if people want (once I get home from the holidays.) Nov 24, 2022 at 21:52
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    @GlennWillen, I (for one) would love some pics if you feel so inclined.
    – Geo...
    Nov 24, 2022 at 22:28
  • This kind of thing was not only a commercial product; IBM themselves sold Selectrics with data storage, that could read from cards, and that could emulate a 2171 terminal. This is because the selectric internally used binary electric inputs to the type system. So effectively, the Selectric was already a printer, just one with a non-standard interface. So while this answer is a good story, it's unfortunately quite far from an answer to the OP's question.
    – cjs
    Nov 25, 2022 at 22:40
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    An IBM electric was/is an impact printer with a typewriter interface. That isn’t what the OP was asking about.
    – Duncan C
    Nov 27, 2022 at 15:17
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In a laboratory setting in the early '80s I used a solenoid device on an IBM typewriter, which covered only the numbers, tab and return. It interefaced to to a scientific instrument and allowed the hardcopy printout of tables of integers. The solenoid "buttons" extended up through the device to allow you to activate those keys by your fingers, if you needed to use the thing for manual typing.

Integers only; no punctuation, no shift, no letters. Just numbers, tab, return. I presume it was made by the specialty instrument manufacturer and sold by them as an accessory (and thus may be off-topic for a question that specifics personal computers).

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  • Can you give us any further information on the scientific instrument, such as what it was, a brand name, and/or other information that would let a researcher try to track it down?
    – cjs
    Nov 25, 2022 at 22:33
  • @cjs One example is mentioned here: canberra-industries-50years.com/1989.html
    – John Doty
    Nov 26, 2022 at 20:09
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My dad built something on our Franklin in the early '80s that turned a used electric typewriter into a decent printer. A board with a rats nest of wires going to the switches on each key of the typewriter, and a TTL multiplexer chip going to IO pins on the computer as I recall. He wrote a little 6502 assembly program with a tuned delay loop to "type" all the letters with enough delay that the typewriter did not jam up. I'm not sure if he read about it in a magazine or just came up with it.

If you had to operate a mechanical typewriter, you'd have to hit the keys pretty hard to actuate them reliably, but I suspect that hobbyists built similar electronic interfaces fairly frequently.

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  • Solenoids with sufficient stroke distance and force to operate a manual typewriter would be far too big and power hungry to be practical. A far more practical way to operate many such mechansims in close proximity to each other would be to have plungers that are held by springs away from a spinning roller, but may be pushed against it. Somewhat conveniently, one could buy typewriters with such mechanisms already installed, which would as a consequence require a solenoid to supply far less mechanical energy.
    – supercat
    Nov 26, 2022 at 7:39
  • This does sound like a complete different solution than the OP asks for, doesn't it?
    – Raffzahn
    Nov 26, 2022 at 21:35
  • @Raffzahn No, it sounds like an very similar solution. In both cases you're emulating a typist closing a switch across the same contacts on the keyboard PCB. That's not nearly so different as, say, skipping the keyboard and input system entirely and generating codes to send to a Selectric print head.
    – cjs
    Nov 28, 2022 at 5:33
  • @cjs "pressing", as asked for, implies mechanical action. Generating the same signals as the switches would isn't "pressing" - as you already describe. More so, the question asks for typewriters, not electric typewriters.
    – Raffzahn
    Nov 28, 2022 at 14:17
  • @supercat Maybe pneumatics? Nov 28, 2022 at 15:29
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For some time you could buy machines that worked like a type writer, but at much higher speed. My company bought a Brother "typewriter" that got connected to a computer and could type at 25 characters per second continuously. That's about eight times my best speed, and the fastest person I have ever seen could do about 600 characters per minute or 10 per second.

So the answer is yes if you decide to call this a typewriter. But the IBM Selectric had computer interfaces as well. But I think it couldn't change heads, so it was unusable for our secretary at a maths institute who typed mathematical texts.

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