[GreenKeys] Telex/TWX?

[jhhaynes at earthlink.net]

TWX goes back to 1932 or so, a Bell System circuit-switched system that
provided 45 baud 60 wpm teletypewriter service between subscribers
in the U.S.  Since it was circuit switched the connections were two-way
end to end; you could carry on a conversation if you wished.  This is
in contrast to telegram service where the message is one way and stored
and forwarded at intermediate relay stations along the way.  TWX until
the dial cutover in the early 1960s used manual switchboards - and the
reason was that nearly all calls were long distance and charged for
by time, so operators produced the time toll tickets that were used
to make the itemized bills, just as in long distance telephone service.

It was an article of faith with Western Union people that Bell's offering
of TWX violated an agreement between the two companies that Bell would
stay out of the telegraph business and W.U. would stay out of the
telephone business.

Telex started in Europe in the 1930s using 50 baud equipment.  Probably
the most well-known system was the German one, which was dialup service.
Long distance telephone and Telex service in Germany used a simplified
billing scheme, in which the customer did not get an itemized bill
listing the places called and call duration.  Rather on completion of
connection the customer's register was connected to a pulse generator,
with the pulse rate determined by the distance covered by the connection.
So the customer got a bill for the number of pulses accumulated in a 
month.  This allowed for long distance dialing service before the 
invention of automatic long distance billing systems.

Telex was more or less interoperable internationally, even though there
were wildly different switching systems in different countries.

Telex came to Canada, and W.U. decided there was a market for the
service in the U.S., competing with TWX.  W.U. bought teleprinters and
switching equipment from Siemens in Germany, and later bought the
Model 32 teleprinters from Teletype in the U.S.  W.U. didn't benefit
much from the international nature of Telex, because the U.S. government
had required W.U. to divest its undersea cable business.  Thus the
international Telex business revenue was shared with RCA and W.U. 
International, a separate company, and other overseas carriers.

TWX originally used DC transmission over telephone lines.  Later there
was a lot of use of 43A1 carrier channel equipment to develop a duplex
telegraph circuit over a voice line.  This kept the telegraph clicks
out of the voice circuits sharing a cable with telephone circuits; and
anyway the Bell System had plenty of voice circuits available between
their offices and those of customers.

By the early 1960s the nationwide U.S. telephone network was substantially
complete, providing customer dialing of all local and long distance calls.
It was an appropriate time for AT&T to move the TWX network on to the
voice network.  Since the amount of telegraph traffic was small compared
with voice traffic it could be handled with very little additon of
equipment and circuits.  Also AT&T decided that 100 wpm ASCII would be
the wave of the future.  The initial cutover to dial TWX kept the 60 wpm
service and started the 100 wpm service in parallel, with the ability
to switch in code converters for connections between the two different
speeds and codes.

I'm of the opinion that getting into Telex was a mistake for W.U., as
it put them into head-to-head competition with AT&T TWX and AT&T owned
the lion's share of both local loops to customer premises and of
intercity transmission bandwidth.  It was an inconvenience to customers
who had to subscribe to both services, much like the early days when
a city would be served by several competing, non-interconnecting
telephone companies.  It required W.U. to spend a lot of money on
electromechanical switching equipment, whereas for AT&T switching
TWX calls was just a marginal expense of using the existing voice
switching equipment.

Meanwhile W.U. had been insisting for years before the FCC that there
should be one national voice carrier, AT&T, and one national telegraph
carrier, W.U.  This argument doesn't make much sense technically,
since the voice switched network was not bad for switching telegraph
and data calls as well.  The switches and trunks don't care whether
it is voice signals or modem tones going through them.

Ultimately AT&T agreed to sell the TWX service to W.U.  Probably neither
company fully realized that both services were in their twilight,
as inexpensive FAX service, using the telephone network, was soon
to take over the market.  One benefit of the sale was that W.U.
provided interconnectivity between the two services.  Things might
have worked out better if the arrangement had been similar to that
of today's competing local telephone service providers.  (Where the
local telephone company provides all the wire and switching and the
"competing" service simply buys it at wholesale from the "real"
telephone company and retails it to the subscribers.)  Instead the
provision was that W.U. would take over the whole TWX network.
AT&T for a limited time allowed W.U. a discount on leased local loops
and the use of their switching equipment; but the arrangement was as
if ultimately W.U. would provide everything and AT&T would be completely
out of the TWX business.

Prior to the sale of TWX, AT&T had attempted to offer another service
called WADS, wide-area-data-service, similar to TWX in some respects
but allowing for customer owned equipment and billed for at a flat
rate like WATS, wide area telephone service.  This was the basis of
a service offered to Delta Airlines and United Airlines even before
dial TWX came into being.  They also envisioned using the #1 electronic
switching system (telephone) in data applications, replacing older
electromechanical teletypewriter switching systems.  As it turned out
FCC did not approve the WADS proposal and that service was never 
developed.  With the sale of TWX to W.U. further work on the #1ESS-ADF
also ceased.

I've never been clear on why W.U. so suddenly fell into insolvency.
Certainly the traditional telegram business was on the way out,
except as it was useful for money transfers.  It has always seemed
to me that it was U.S. government policy to keep W.U. with exactly
one foot in the grave at all times.


jhhaynes at earthlink dot net