[GreenKeys] 60 ma current loop to RS232 converter

[Paul Heller]

Mike,

What you thinking of doing will not work. ITTY is a broadcast only system and follows RTTY conventions, so it has frequency tones. In order to listen to it, you need an HF modem or a TU (terminal unit). These devices provide the current loop and also translate the tone frequencies into baudot pulses on the loop that drive the teletype. They are not expensive (well normally not) on eBay, and others on this list might have extras.  ITTY is fun because it broadcasts news 24/7. There is also an AUTOSTART channel for ITTY that only occasionally sends out bulletins. For example, each and every greenkeys email is sent out the Autostart channel. There is also a news of the day broadcast. And anyone can send a file to AUTOSTART and it will be broadcast out one time.  Occasionally there is a picture show on AUTOSTART.

The second problem you will have is the speed of your teletype. Out of the factory, model 32 teletypes were 66 WPM (words per minute). RTTY (and ITTY) are normally 60 WPM (45.45 baud). That said, the Europe channel of ITTY broadcasts European news 24/7 at 66WPM (50 baud). You might have a teletype that had a gear change to get it to 60WPM, but if not you will be inconsistent with other teletypes and with ITTY.


If you want to talk to people, I recommend you look at i-Telex. There are a number of us greenkeys people on i-Telex, and many more non-greenkeys people around the world. It’s quite fun. You can find information about it at: https://www.i-telex.net.  That site is in German so might not be completely readable for you,  but if you click the links and such you can find photos and prices. It is not hard to build up a system, but you need the boards and a power source. You need to buy at least four boards:

1. Stromversorgung. This is the power board
2. iTelex. This is the brains
3. TW39. This is the original telex interface board with the same standards that your teletype originally used when it was in production
4. Backpanel. This is the backplane the other boards plug in to.

You will also need a transformer (readily available) and need to wire that up . And you will very likely need to change some resistors in your teletype. Several of us have done this and can guide you, but be aware you need to be comfortable with a soldering iron. The advantage of this is that your machine is being used in the manner it was originally designed for. And it works at 66WPM (50 baud). You even get to use the rotary dial to call the other party! And there is nothing like a good old fashioned telex conversation.


It’s just like a RTTY conversation, which is another option but you would have to be a licensed amateur radio operator and use above said HF modem . I’m guessing you might not be.

As for “conversing” with others in some other manner, RS232 or otherwise, over the internet —  I’m not sure of a system that does that. One of these days I might make ITTY two-way.  Other’s might now. But keep in mind that most other teletypes operate at the slower 60WPM. That speed needs to be matched on each end your you need a speed converter. Some of the modems/TUs can do speed conversion.


Paul
W2TTY
i-Telex: 80003

ITTY:  		HTTP://INTERNET-TTY.NET:8000/ITTY
AUTOSTART:  HTTP://INTERNET-TTY.NET:8030/AUTOSTART
EUROPE: 	HTTP://INTERNET-TTY.NET:8040/EUROPE




> On Feb 23, 2018, at 1:10 PM, Michael via GreenKeys <greenkeys at mailman.qth.net> wrote:
> 
> Does anyone know where to buy or how to make a 60 MA current loop to RS232 converter that will power the loop needed to connect to a Model 32TT and let me plug into an RS232 port on a PC? Then I can connect to the HTTP://INTERNET-TTY.NET:8000/ITTY <http://internet-tty.net:8000/ITTY> and talk to others by TTY, I assume....?
> 
> Thanks,
> 
> Mike
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