[GreenKeys] Telex/TWX?

[wa3frp at aol.com]

Hi Henning!

Those wonderful TW39 and TW55 exchanges!  The TW39 was quite large, 
assembled in relay racks and painted grey.  This was a nice Central 
Office exchange.  We had one of these exchanges in Philadelphia and 
also a TW39 in Pittsburgh.  The TW 55 was a smaller exchange and I only 
saw one of these.  The TW55 was a line concentrator used at a smaller 
office.  I believe that there was a TW55 in Reading Pennsylvania.

Then there was the super large Siemens TWM-2 Telex exchanges in New 
York City, Washington, Kansas City, Atlanta, Chicago, Los Angeles and 
San Francisco.  That was an exchange.  It was nice to just stand 
quietly in one of those exchanges and listen to the sounds that they 
produced while setting up and tearing down call paths.

The TW39 and TW55 exchanges gave way to the Siemens TWK3 and TWK4 
exchanges that used the wonderfully engineered ESK relays.

In the end, there was another super large Siemens Telex Exchange in New 
York City that Western Union used to switch voice traffic but I only 
visited the site to see old friends and can't remember its 
nomenclature. And, it was over twenty years ago!  Nice memories...

73

Russ
PS we should have a RTTY QSO one day on 20M - maybe at 1300-1400 UTC...

-----Original Message-----
From: henning at teleprinter.net
To: greenkeys at mailman.qth.net
Cc: s.hallas at ntlworld.com
Sent: Thu, 25 Jan 2007 6:03 PM
Subject: Re: [GreenKeys] Telex/TWX?

Hello Sam and others,

well, here some facts from Germany and other countries I know:

The Siemens company started the first automatically operated Telex 
network in
1931 between the two cities of Berlin and Hamburg. Soon it grew all 
over Germany
and Europe.

It was derivated from the telephone exchange technology with rotary 
pulse
diallers (what you in UK and other countries call Strowger selectors), 
but all
based on current loop telegraph technology with 40 ma 120 volts.
Lines from exchange to subscriber were mainly two wire single current, 
for
logner distances in country side areas 4 (3) wire double current +/- 60 
volts
40ma was in use. But double current was very rare. Although I have also 
never
been professionally in Telex service I would say over 90 percent was 
single
current subscriber line technology.
This whole systems was called TW 39 / TW 55 (from Teilnehmer 
Waehlsystem
1939/1955 which you could translate as subscriber dial up system).
This techology lasted in Germany until the mid 1970s. Then it was 
changed over
to a kind of modem tone frequency system with unfortunately proprietary 
tone
pairs (called System ED 1000) made by Siemens.
In order to use the old mechanical TW39 machines after system change, a 
kind of
modem connected between the machine and the line to the exchange was 
need now.
This ED1000 Telex system is still in use for the last remaining Telex
subscribers here in Germany. Mostly banks and shipping companies. The 
total of
still remaining Telex subscribers is estimated around 1,000 - 2,000.
In it's peak in the 1980s the German Telex network had over 150,000 
subscribers.
Machines were only Siemens and Lorenz (SEL) machines. They were 
property of the
subscriber but perfectly maintained by the German Post as maintenance 
of the
machine was included in the monthly line rental fee.
Please see my website www.teleprinter.net for the models that were in 
use. It
started from Lorenz Lo15 (licenced model 15) and Siemens T37 until the 
last
Lo3003 and Siemens T1200.

In East Germany (GDR) a TW39 current loop system was in use until the
reunification with West Germany. Then the East German Telex network was
incorporated into the West German system.
Machines there were only RFT (of course ;-) ). Mostly mechanical RFT 
T51, which
was a Siemens T37.

Austria first also had a TW39 system Telex network. But later changed 
to a
derivate of V.21 subscriber line tone system insted of using the German 
ED1000
system.
Additional to Siemens and Lorenz machines, there also Olivetti machines 
were in
use. Network has been already switched off.

The Netherlands used also a TW39 system, but with keyboard (Baudot) 
dialling
instead of pulse dialling with a rotary dialler.
In late 1980s they switched over to a V.21 tone frequency system. As 
far as I
know their Telex also still exists.

Italy also used a double current TW39 system with keyboard (Baudot) 
dialling.
Machines of course mainly Olivetti.

Czechoslovakia also used TW39 like Germany. First with mainly RFT T51 
machines
and later with Siemens T100 licenced model.

The UK used a double current +/- 80 volts system so far I know. But I 
am sure
Sam or Larry can tell more about that.

Form Australia I know that there also was a double current network in 
use. First
starting manually switched and later changed to automatical switching 
dial up
network.
Early machines were Creed 7b, later mainly Siemens T100 (M100) and then 
in the
electronic age all kinds of Sagem from France.
But here also Larry can tell more...

BTW: A couple of years we started an automatical dial up network over 
telephone
lines, we call TelexPhone. Our PC board (using a PIC) emulates the 
functionality
of a TW39 exchange with it's signalling protocol. So you can more or 
less easily
;-) connect an old TW39/55 machine with its control unit and chat over 
telephone
lines. We are a growing community and have much chatting and telexing 
over phone
like in real in the old days.

rgds,
Henning DF3OE +++

www.teleprinter.net


---------- Original Message ----------------------------------
From: Sam Hallas <s.hallas at ntlworld.com>
Date:  Thu, 25 Jan 2007 22:08:53 +0000

>WA3FRP at aol.com wrote:
>>
>> Hi!   I'm a retired  Western Union guy! etc
>
>Fascinating stuff from all the correspondents on this thread. I was
>hoping that some of our experts from 'the rest of the world' would 
chip
>in with details about what machines were used in Europe/ Australasia 
etc
>on the 50 Baud, ITA2 telex network. Henning? Larry?
>
>Cheers,
>Sam (only a telephone engineer, never actively involved with the telex
>network)
>
>
>_______________________________________________
>GreenKeys mailing list
>GreenKeys at mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/greenkeys
>





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