The German company TeKaDe produced teletypes for the German military (Bundeswehr). The gray office version FS220(Z) was delivered with the well known TW39-interface and was powered with 220 volts. The green portable/outdoor version FS200(Z) comes with V.10-interface and a power connector for a 24 volt truck battery. This teletype was build to work with the control device (FSG) FAG200 which converts the V.10 signal to TW39 or ED1000.

Nowadays the teletypes are not longer used by the military and sold out on eBay and some military shops.

For FS200 / FS220 images see https://old.fernschreibamt-hausneindorf.de/html/tekade_fs220.html

Name	Pin*	Description
D1	2	Transmit data (teletype out). The levels are -5...-6V for SPACE and +5...6V for MARK.
D2	3	Receive data (teletype in). The levels are -5...0V for SPACE and +5...6V for MARK. Some V.10-cards are not working with 0V for SPACE; they need at least -0.05V.
Betr.b.	20	When Telex is powered up, the "Beriebsbereit" (German for "ready for use") is set from 0V to +5V.
S2	4	When LIN-button (equal to AT-button on FSG) is pressed, S2 changes from -5...-6V to +5...6V and line communication is active.
M2	5	A rising edge (negative to positive) on M2 makes a short beep sound. Other dependencies to this pin are not known. Some of the V.10-cards starts a permanent beep which can only be stopped by power off.
ARQ	17	This is used to request a saved message from teletype (not used in this project).
?	6	A wire is connected to pin 6 in Sub-D-connector but not connected inside the V.10-card.
E...	7, 9, 11, (12, 13, 14)	Ground

*) Pins on 25 pin Sub-D male plug.

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The FS200 (or FS220 with V.10-interface-board) can be connected directly to a PC or Raspberry Pi without any FSG. Only a USB-serial-adapter and some wires are needed.

The V.10 definition is near to V.24 (RS-232) with a voltage limit of -6...6V. Modern USB-adapters use a voltage range of about -5...5V. So the two 'worlds' can be connected without any hardware damage.

In online stores one can find adapter cables which convert USB to RS-232 (not TTL) with a 9-pin Sub-D connector.

All you need for communication with the teletype are two connectors and wires (the gray connections are optional):

This works with the FS220/FS200 set to Dx (full duplex) and echoed characters back by software.

If you want to have a local echo (seeing own typed character) then switch the FS220/FS200 to HDx (half duplex) and use the following hack schematics:

Electronic parts:

• Diodes: 1N4148
• R_Loop (near diodes): 2.2 kOhm
• R_LED : 1 kOhm

With this change and duplex switch set to HDx the own typed text is printed in red and the text from the PC/RPi is printed in black.

Optional a LED can be connected between DTR and ground to display an established connection or whatever the software signals with the DTR line.

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If you want to have a local echo (seeing own typed character) then switch the FS220/FS200 to HDx (half duplex) and use the following hack schematics:

Electronic parts:

• Driver: 74HCT00
• R_Level (TTL in/out): 2.2 kOhm
• R_LED: 470 Ohm
• C: 10µF 10V Low ESR or Tantal

The 2.2kOhm resistors are used to limit the current in the suppressor diodes. The limit is needed from -5...5V to TTL-5V-level as well as from TTL-5V-level to TTL-3.3V-level. Te resistor between D1 and D2 is a Hack to move the D2-level a little bit to negative to support all V.10-FS200-cards.

With this change and duplex switch set to HDx the own typed text is printed in red and the text from the PC/RPi is printed in black.

An optional LED can be connected between relay-output GPIO and ground to display ready-for-dial state and an established connection.