Siemens S 22759 keyboard - Siemens STB 21 switche

[boxboxbox]

Hello, a week ago I found a offer of a Siemens board that looked quite interesting so I started to lurk and find as much information about it as possible.

IMG_20210402_154759.jpg (2.56 MiB) Viewed 3162 times

(Sorry that it's so dirty, I didn't assemble it back yet but I did clean the case and keycaps already)

IMG_20210402_160654.jpg (2.55 MiB) Viewed 3162 times

Turns out that was harder than I anticipated, as the only info about the same model I could find was posted here, by user PlacaFromHell on this post;
viewtopic.php?t=19886

The keyboard has a few different keycap sets in different languages from what I've gathered, this one is in a Polish layout, the one posted by PlacaFromHell was in spanish so I reckon there was quite a few layouts.
From what I understand they keyboard was used in telephonic communication with such buttons as "Connect 1-5", "Subscription type", "Break" or "Hang up", as well as all of the funny Polish letters such as "Ż", "Ń", and even "Ź, Ó" and "Ę, Ą" on the same button.

The switches are bit more interesting, as they are Siemens ST 21 tactile switches. They're really nice to be honest, although the tactlity is a bit light it still gives some nice feedback while typing. Problem being that some of them are a bit scratchy, possibly from dirt and dust. I'll see if I can desolder some and clean em, as the spacebar switch is especially bindy and scratchy.

IMG_20210403_175633.jpg (2.08 MiB) Viewed 3162 times

IMG_20210403_175623.jpg (2.19 MiB) Viewed 3162 times

IMG_20210403_180319.jpg (2.69 MiB) Viewed 3162 times

The resistor and metal leaf have two pins each, making up for four pins in total.

If you're wondering where are the pins, well, it's a funny story, as one of the switches came loose from the pcb while I was taking off the keycaps, while I was trying to shake off some dust from the pcb it just came off and left the pins soldered in. Too bad, but at least I got to take a few pictures of it.

IMG_20210403_172147.jpg (2.05 MiB) Viewed 3162 times

IMG_20210403_175548.jpg (2.42 MiB) Viewed 3162 times

Sorry for the hardware gore haha.

The cable is quite bizarre, reminds me of the VGA cable, but has only 9 pins.

photo_2021-04-03_23-35-44 (5).jpg (36.65 KiB) Viewed 3162 times

And here's what it connects to, another 9 pin connector with what I believe is a ground connector as well.

IMG_20210403_171908.jpg (3.27 MiB) Viewed 3162 times

Now, I'll be honest, I'm no expert in electronics, but the thoughts of making a converter for this keyboard have been bugging me, I'd do it myself if I knew how to, but would it be possible to make a converter for this keyboard?

Anyhow, that's my find, got real lucky with it.

Thanks for reading and I'll upload some pics when I assemble the keyboard back together, peace!

[Lalaland124]

Very nice board! Well you could try to trace the keyboard matrix and solder it to a Teensy or just hand solder the whole thing altogether. I'm no expert on this but there are people who already did that if you search on deskthority

[Jan Pospisil]

I'd be curious to see someone convert these. I do have a Siemens, though not the exact same model, but it does have that kind of connector.

[John Doe]

Very impressive layout, wish to have one to get fun.

[Muirium]

Well kbdbabel.org has the plug.



Those caps are real pretty!

Here’s the switch.



Those aren’t resistors: they are diodes. Which means this keyboard ought to be NKRO, which is always a relief!

They do have a right direction and a wrong direction though. (Keep track of which side the stripe goes) So beware of that!

[boxboxbox]

Those aren’t resistors: they are diodes.

Ah, thank you for correcting me, sorry about that. At least the n-key rollover feature is presant haha, I'll be able to press more than two keys at once.

About that plug... That diagram barely tells me anything but thank you for sharing it with me, kbdbabel.org has pretty interesting content on vintage connectors!

Also I got the keycaps and case all nice and clean!

IMG_20210404_202457.jpg (2.83 MiB) Viewed 2999 times

[gichtl]

Well kbdbabel.org has the plug.
[7KQ1100]

I disagree with 7KQ1100. In the picture you can see the DS26LS33ACN which is a Quadruple Differential Line Receiver, so the interface is for sure ITU V.11 (also known as TIA/EIA-422) like many other Siemens keyboards. So you should also find some 26LS31A for the sending direction. Protocol is 600 Baud, 8 bits, no parity, 1 startbit, 1 stopbit.

I have some other keyboard with the following pinout:
1 DIN-P
2 ---
3 DOUT-P
4 +5V
5 0V
6 DIN-N
7 ---
8 DOUT-N
9 +5V

But you better should follow the traces from the transceiver circuits.

To see this working, you could get some RS-422 converter and connect with Hyperterminal. But don't confuse with RS-485, which have only one pair of wires instead of RS-422 which has two pairs of wires.

[Rayndalf]

So those are Siemens switches! I have a couple control panels that use the same switches + type of caps. Got them from some cool guy on Reddit who saved them from getting scrapped with the rest of the systems.

I really need to actually do something with them. The caps and switches are surprisingly nice for the shorter height.