Siemens 1200CT (CPU)

In Germany, Siemens always was the primary electronics manufacturer. Since 1950s they are involved in telecommunication devices production and they made most German telephone switching machines. Among telephones, typewriters and computers they produced teletypes since 1950s or even earlier. First teletypes were mechanical, using mechanical multiplexers and electric typewriter mechanisms as printers. But the last ones were fully computerized.
Computerized teletypes line, Siemens T1000, started in 1980s with all-in-one teletype systems which look like electric typewriter with additional box for electronics and display. They contained a complete dedicated system which included teletype equipment and printer. Everything except floppy disk drive was enclosed in a large, single casing. Later, smaller T1200 versions with built-in printer(T1200SD) came out as well as versions containing monitor and floppy disk drives to store messages and templates. First attempt of T1200 with CRT was 1200BS with not easily detachable monitor. Inside, they still contained dedicated computer system. But later, Siemens released another machine: The T1200CT.
1200CT has a complete IBM PC XT clone inside, implemented on a single ISA board. Teletype logic and modem are on separate ISA board. Monitor and printer are detachable and PC compatible. Although PC XT keyboard may be used, the original keyboard is different as it has teletype keys. The computer has a single 3.5" 720kB floppy disk drive as storage. Additionally, battery-backed RTC and memory for text is present.
I don't know if Siemens manufactured any teletypes after this one. As in Germany in early 1990s Teletype service was phased out, 1200CT was mainly sold in countries other than Germany. It has localized firmware to be used in other countries.

Manufacturer Siemens

Origin Germany (West)
Year of unit 1991
Year of introduction 1988?
Class XT
CPU Intel 8088
Speed 8MHz
RAM 512kB
ROM BIOS, Teletype environment (640kB)
Graphics 80x25 Text, CGA-compatible?
Sound PC Speaker
System expansion bus 8-bit ISA
Floppy/removable media drives 1x 3.5" 720kB floppy disk drive


Hard disk: None


Peripherals in collection:
 - None

Other boards:


Teletype board with its of in-ROM OS (probably MS-DOS 3.2 or 4.0)
Non-standard expansions:  -
Operating system(s): MS-DOS

My unit has been salvaged from scrap electronics, unfortunately the keyboard, monitor and printer was not present there. The rechargeable battery has been removed right before it destroyed other parts. It has Polish firmware and was probably used in Poland, as in Poland teletype service was available until 2007 (yet most companies dumped teletypes in late 1990s). The picture on the right comes probably from user's manual.

Contents: Starting, usage Links


Remember to remove rechargeable battery from teletype board! It will leak and destroy electronics!

After Award BIOS, the PC tries to boot from ROMs and if it fails, from floppy drive. By default it boots from 640kB of ROM present on teletype board. It runs embedded DOS and probably compressed teletype program. From this programt here is no way to escape to DOS.

The "ON/OFF" switch present on teletype board turns embedded rechargeable battery on and off and it has nothing to cards boot-up at all.

To boot the system from floppy disk, you have to remove teletype board. Disassemble the PC by releasing two latches from top on the rear. Open the cover towards front. Loosen two screws and by pressing plastic bracket pull the CPU shield from the computer, loosen its screws, remove cover and you are inside.

I think that it may be possible to install a HDD in it by using these small controller boards with MFM/RLL hard drives installed on their rear in a metal skeleton.







Links: - Look for "Die ganze Textleistung" - cover of manual? - According to this page T1200BS is the last produced model by Siemens. Well, not. - Pictures of T1200BS internals.