Example with Raspberry Pi for teletypes with FSG

Hardware for TW39 High Voltage

Raspberry Pi Zero W with DIY TW39 board

Combination with power transistor on heatsink

2-sided PCB. Design files can be found in project https://github.com/fablab-wue/piTelex.supplement

Schematics

Parts

Part	Description
ULN2x03	Open collector driver with 3.3V TTL input compatibility. ULN2003 has 7 drivers. ULN2803 has 8 drivers
TIP47	Any NPN power transistor with heatsink for 2W power and U_CE >= 120V
BCxxx	Any small NPN transistor (e.g. BC546)
LTV817	Any optocoupler with more than 50% (e.g. PC817)
1N400x	Any rectifier diode (e.g. 1N4007)
Relay	Small signal print relay with two changeover contacts and a rated coil voltage of 5V (e.g. Finder 30.22.7.005.0010)
Potentiometer	1 or 10 turn with 0.2W. Used to calibrate the regulated 40mA current loop
Resistors	Standard 1/8W

Pin Connection for RPi

function	GPIO pin ( GPIO #)
TXD	11 (17)
RXD	13 (27)
Number Switch	31 (6) (connected to RXD)
Relay	15 (22)
GND	6 and/or 9, 14, 20, 25, 30, 34, 39
5V	2 or 4

Note: These are the default pins. Other combinations can be set in telex.json file.

RPi Pinout

Note: For pulse dial in I-loop connect pin 13 (RXD) with pin 31 (DIAL_SW) and configure GPIO 6 for 'pin_number_switch' in txConfig.json file.

Interface Connection

Whole System in a Box

With a Raspberry Pi and the self-made-PCB in the middle. A DC/DC (Step-Up) for 60V on the left and a DC/DC (Step-Down) for the RPis 5V at front. It is powered by a wall-power-supply with 12V...24V.

This is all you need to connect a teletype (with FSG) to the i-Telex network over internet.

Whole System in a BIG Box

The same interface as above but with an integrated transformer and an ADo8 plug.

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Software

For Installation see SW_Install

This electronic is handled by the software module RPiTTY.

Start the program: Change to the piTelex directory and enter

./telex.py 

*Note: Add the argument -I 2342 to start the i-Telex client and server at port 2342. Or better configure i-Telex functionality directly in the configuration file (default telex.json). See Configuration File