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Old 12th May 2020, 12:28 pm   #1
veedub565
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Default Question about Telex

I'm not sure if I should be posting this in this forum or the military radio forum. It is Telecoms/Telex related though, so here goes.

I have a HF radio set (Plessey TRP8255) and I want to try and use it for data communications. The set can be remote controlled via RS232 which is fine. I can just hook it up to the PC serial port.

It also has the following connections available:
  • Telex In (600 ohms audio input, TELEX mode)
  • Ground
  • Aux In (600 ohms audio input, USB,LSB, AM, R3E modes)
  • Ground
  • Line Out (600 ohms audio output)
  • Ground

It has an (optional) Line Transformer Board fitted providing a balanced input/output.

Would I be right in thinking that these audio lines should go to the Line in/out of the soundcard on the PC ?

To start with I want to have a go at some basic RTTY and learn, but in future it would be nice to set it up with a proper vintage period dumb terminal and/or teleprinter machine. Just for the satisfaction of making it work and having it physically print something out upon receipt of some data.

I don't know if telex/teleprinter machines work that way with 600 ohm audio lines ? Also as I understand it (and I may be wrong) Telex is purely on a dumb terminal, and Teleprinter is like a typewriter keyboard with a printer. Sometimes you get both combined a la' BT Cheatah 87C

Please set me straight if I'm wrong on all this, it seems a fascinating thing to get into but I'm just really learning about it at the moment.

Ben
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Old 12th May 2020, 12:51 pm   #2
Dave757
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Default Re: Question about Telex

Hi Ben,

Can't comment on the connections to the Plessey, but Telex is an international
dial up telegraphic communication system , using Teleprinters at 50 Baud. I don't
know if it is still operational though. The BT Cheetah was a teleprinter supplied by BT
as a terminal for Telex.

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Old 12th May 2020, 12:59 pm   #3
Pellseinydd
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Default Re: Question about Telex

The Telex network as such was shut down some years ago. There is now a Swiss company that use the term but basically it is an email system working over the Internet.

Originally it used 80v+ and 80v- for signalling. In later years (1980's) there were PC based setups with a modem that worked back to the Telex exchanges. I worked for Plessey at the time and we used to maintain the setups - a modem, printer, control unit, VDU & keyboard.

Be interesting to see what the unit was used with?
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Old 12th May 2020, 2:46 pm   #4
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Default Re: Question about Telex

There is something called radio telex still used in the maritime sector .

https://en.wikipedia.org/wiki/Radioteletype

Its used in the Global distress system i think.
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Old 12th May 2020, 3:28 pm   #5
veedub565
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Default Re: Question about Telex

Thanks for the replies,so looks like Telex may be a non starter then.

The Plessey TRP8255 was used by the signals regiment in NCRS trailers, in the 80's think. The MOD had it connected up to:

Plessey PV 3559 HF Modem
Plessey PV 3558
HF Adaptive prosser
Plessey HF/HF co-site filter PV3560

So this is more vintage radio, than telephony. Possibly yes maritime radiotelex is more likely as it is essentially a maritime radio set at heart.

I'd be interested to learn more about the Plessey systems
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Old 12th May 2020, 4:19 pm   #6
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Default Re: Question about Telex

I believe that a few years ago telex was still being used to broadcast information to fire stations. I don't know if this service is still operational.
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Old 12th May 2020, 4:28 pm   #7
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Default Re: Question about Telex

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Originally Posted by emeritus View Post
I believe that a few years ago telex was still being used to broadcast information to fire stations. I don't know if this service is still operational.
'Telex' was an automatic teleprinter switching system run by the GPO/PO/BT in the UK linking to similar systems overseas - the term 'telex' is now often used for teleprinter working be it point to point (as was often the case with the military - speaking with an old khaki peaked cap with R.Signals badge!). During my days with the GPO, our fire service had direct teleprinter links to fire stations using what was then known as the 'Surrey' system.
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Old 12th May 2020, 5:08 pm   #8
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Default Re: Question about Telex

By pure chance I had a PC Telex modem on the bench a couple of days ago. It was made by a company called 'Hasler' and the unit is named the 'ProTelex'. Inside is a V21 type modem (here used at 50Baud half duplex) and a board containing an 8085 processor, 12K firmware, etc which handles the conversion between ASCII and ITA2 (incorrectly called Murray code), modem control, etc.

No idea what I'll use it for but I have all sorts of odd things in the collection...
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Old 12th May 2020, 6:29 pm   #9
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Default Re: Question about Telex

RYRYRYRYRY

Ben

It is perfectly possible to connect a mechanical TELEX machine to a radio

You need a modem to convert those audio signals from your radio into suitable signalling to the telex machine mechanics and vice versa

Since the advent of personal computers the "machine" part has gone "software" but a few diehards in amateur radio still do it with TTY machines

Over the air is is called "RTTY" (radio teletype) and is based around Baudot not ASCII coding

BARTG (bartg.org.uk) is the amateur group focussed on this subject and have a helpful document here, although it focuses more on using a PC

https://drive.google.com/file/d/1J_j...dIgB7Xdms/view

BARTG was years ago the source of the modem hardware design/kits to interface a mechanical terminal with a design called the "ST5" AFAIR

http://www.baudot.net/creed/docs-ala...e-easy-way.pdf seems more relevant to what you want to do

(The fire mobilising data system I was involved with (35 years ago) used a radio link bearer to pass signals that the fire station did print on a mechanical teleprinter like printer!)

Good luck with your project

Fred
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Old 12th May 2020, 7:40 pm   #10
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Default Re: Question about Telex

If you have Grandchildren and condemned to watch Fireman Sam, they still do!
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Old 12th May 2020, 8:23 pm   #11
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Default Re: Question about Telex

Hi,
this thread is most useful, as I have a Portaview Jr 32 which I was thinking about restoring. this is a telecommunication device for the deaf..
and looks like an acoustic coupler with a display and keyboard.
I think probably seeing a Creed 7B ? being used back in the 1970's at an exhibition at my Secondary School got me interested in rtty.
there was also a printer / terminal used to access a main frame computer. But I can't remember enough about that ...
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Old 13th May 2020, 7:44 am   #12
veedub565
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Default Re: Question about Telex

Thanks Fred,

That's useful to know about the modem, so that's the part that has the audio connections. I need to keep an eye out for a suitable one of these. I'll prob want to get it working on RTTY with the PC to start with. Thanks for the link to BARTG, I'd heard there was a dedicated resource for this but couldn't for the life of me remember the name.

Ben
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Old 13th May 2020, 9:10 am   #13
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Default Re: Question about Telex

One of the best Terminal Units is the BARTG ST-5, I am sure we can find you the information to build one and I keep the torroids in stock. I am an avid user of RTTY and am currently doing it on an Arduino display unit I built. I would really love a teleprinter, pref a 444 but there are just none about (bar the one that went for silly money recently on Ebay!).

If you want a 50 Baud test signal, tune just above 10MHz where you will find the German shipping forecasts.
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Old 14th May 2020, 1:12 pm   #14
veedub565
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Default Re: Question about Telex

I'm just reading the through the RTTY The Easy way booklet and exploring the BARTG site now. Looks like the homebrew Terminal Unit is the way forward.

I noticed the booklet mentions AMTOR. I actually have an AMTOR unit, a model 10-A Telereader R/T Convertor. I eneded up with it without really understanding what it is or does.I kept hold of it though. As far as I know though AMTOR is a data mode like RTTY, and pretty much defunct now.
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Old 14th May 2020, 5:20 pm   #15
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Default Re: Question about Telex

Quote:
Originally Posted by Scimitar View Post
One of the best Terminal Units is the BARTG ST-5, I am sure we can find you the information to build one and I keep the torroids in stock. I am an avid user of RTTY and am currently doing it on an Arduino display unit I built. I would really love a teleprinter, pref a 444 but there are just none about (bar the one that went for silly money recently on Ebay!).

If you want a 50 Baud test signal, tune just above 10MHz where you will find the German shipping forecasts.
There is a 444 on eBay at the moment up to 255 - last 444 went for 205 .

I should really get around to getting the ones I've got kindly 'donated' by BT when I was recovering telephone exchange bits and pieces for preservation in the 1990's. Even got the teleprinter table and the Telex units with the PSU for the 444 built in..

Also picked an ST5 up for peanuts a year or two ago. Just getting around to getting a TX/RX other than the 70cm ones I already have.

I J
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Old 14th May 2020, 5:40 pm   #16
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Default Re: Question about Telex

That's just silly money! I will just have to manage without unfortunately.
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Old 17th May 2020, 3:16 pm   #17
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Quote:
Originally Posted by Scimitar View Post
That's just silly money! I will just have to manage without unfortunately.
Someone has got 'silly money' !! Went for 740 !! Looks like I could have a round the World trip with the ones I've got hidden away
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Old 17th May 2020, 3:25 pm   #18
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Default Re: Question about Telex

There has to be something dodgy about it, no way is its value anything like that. I would pay up to 100 for a good one with stand and I reckon that's generous. Looks like I will be out of luck though!
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Old 17th May 2020, 11:20 pm   #19
Dave757
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Default Re: Question about Telex

Quote:
Originally Posted by veedub565 View Post

I noticed the booklet mentions AMTOR. I actually have an AMTOR unit, a model 10-A Telereader R/T Convertor. I eneded up with it without really understanding what it is or does.I kept hold of it though. As far as I know though AMTOR is a data mode like RTTY, and pretty much defunct now.
Hi,

You would probably find that it would work fine receiving NAVTEX on 490 and
518 kHz which uses SITOR, a similar system.

Kind regards
Dave
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Old 20th May 2020, 7:54 am   #20
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Default Re: Question about Telex

Telex is still alive and well I-Telex - Internet Connected Teleprinter Network.

www.i-telex.net and www.telexforum.de

Please do not be put off by the German language - a lot of members speak very good English and are very helpful.

Going back to the original question, the audio in will be expecting AFSK (Audio Frequency Shift Keying)

The output of a soundcard RTTY program will work, but you will need to faff around with the audio levels, and possible matching, though this is probably not critical.

The line out will go to your soundcard input - again levels will need adjusting.

Beware ground loops, and potential oddball things like the radio ground not actually being at ground at all.....
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