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Siemens T4000 (T4200)

The Siemens T4200 is a kick-ass electronic screen-typewriter system from the '80s with a not less kick-ass keyboard: the Siemens T4000.
Published June 22, 2023
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As it often happens, I bought something because it looked interesting while I had no idea what it was exactly.

This beauty was patiently waiting for a new owner on a local classified site, for weeks, before I finally gave in. Unfortunately, I only have the keyboard, which made my initial attempts to dig up more info on it quite hard in the beginning. The "Siemens schreibmaschine" keyword eventually revealed the solution. (Thanks for the tip inozenz!)

Pic: Source: elka

Source: elka

This Siemens Tastatur 4000 was part of the Siemens T4200, which is kind of an early word-processor and electric typewriter system with a bulky printer and a cute little screen – used to print, edit and store texts, as well as to communicate via teletex.

Teletex (not telex, not teletext)

I'm old enough to remember the days of telex, telefax and teletext, but as of my understanding, teletex is a different service and technology, an upgrade to the telex service with increased transmission speeds. And in the '80s, having a Siemens T4200 granted you access to both telex and teletex services.

Pic: Siemens T4200 (photo by Marion Kaiser)

Siemens T4200 (photo by Marion Kaiser)

The keyboard

Even without the screen and printer, this keyboard has some pretty interesting features starting with the physical key, the array of toggle switches and the way it's assembled together to the mechanism adjusting the typing angle.

Pic: Siemens Tastatur 4000

Siemens Tastatur 4000

The key

OK, I have to admit this was the selling-point convincing me about this purchase: an actual physical key. Before I knew what this keyboard was used for I thought the key was kind of a safety measure to turn on the system, but it's more for selecting the operation mode.


Toggle switches

While the 10 black switches lining up at the top part of the keyboard look the same, they are actually very different. Some have two positions, some others three. Some are springy momentary switches with linear feel, jumping back to their neutral position after flipping them, some other toggle switches are tactile. Some click in one or more positions.



The board features Siemens's in-house STB 11 switches. These linear metal lief switches with 4mm travel, 75cN actuation, and the Siemens logo where introduced in 1980.

Deskthority has a page for these switches showing the internals and pointing to the actual Siemens patent.

Pic: Siemens D11 keyswitch

Siemens D11 keyswitch

Well, they are very scratchy, but relatively low-profile ones for the standards – or better said standard-less times – of the early '80s.


The caps are double-shot, their shape is similar to those I've seen on other Siemens, Tandberg and Reuters boards, or even the MX-compatible Doys and BLOCK caps, but still slightly different: if you look closer, they are circular at the base – with oval top surfaces.


The caps are said to be RAFI mount, with 5x5mm square stems. As OleVoip pointed out, a similar switch with compatible stem was patented in 1975 by RAFI.

However, the mount may be older and may have been invented not by RAFI at all. But for all we know, RAFI were the first to use it with a low-profile switch; that's why we call it the RAFI mount – OleVoip.


The keycaps of the left function and right navigation cluster are flat, many of them with indicator LEDs.


Adjusting the typing angle

This is so cool. No flipping legs, but a clever system to adjust the typing angle seamlessly.

Pic: Setting the typing angle

Setting the typing angle


Screwless assembly

Beside maybe four screws, two of them fixing the display to the PCB, I haven't met any screws inside this keyboard. The top and bottom plastic parts of the case are held together by a springy mechanism, and a similar method is used to clamp the plate and PCB to the bottom case: thick springy wires lock the parts firmly in place.

Pic: No screws

No screws


Built-in manual

While it's called "manual" (Bedienungsanleitung), the hard plastic sheet concealed in the case is rather a cheat sheet you can pull out and use as a quick reference.

Pic: Here..



Pic: ...comes!


Typing test

This is not my video, but dragonforces made a good job introducing the functions of the T4200 as well as providing a short typing demo (from 1:13):


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Published on Thu 22nd Jun 2023. Featured in KBD #125.


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