[GreenKeys] Economist on Telex

[wa3frp at aol.com]

Telex first used two forms of DC transmission from exchange to customer 
location.  The first option, sometimes called local or loop service, 
provided a 60 milliampere loop circuit from the exchange to the 
customer teleprinter. The second option, sometimes called long distance 
or polar was used when a 60 milliampere connection could not be 
achieved, provided a ground return polar circuit using 35 milliamperes 
on separate send and receive wires.

By the 1970s, and under pressure from the Bell operating companies 
wanting to modernize their cable plant and lower the adjacent circuit 
noise that these telex circuits sometimes caused, Western Union 
migrated customers to a third option called F1F2. This F1F2 option 
replaced the dc voltage of the local and long distance options with 
modems at the exchange and subscriber ends of the telex circuit.

Telex was a dial service, like telephone (POTS), using a dedicated line 
 from the exchange to the subscriber. The dedicated line (loop) was 
usually provided by Ma Bell.  There were exceptions when Western Union 
had available cable plant in the area but this was generally limited to 
the major metropolitan cites of New York, Chicago, San Francisco, Los 
Angeles, Kansas City, Atlanta, Dallas, Philadelphia and Boston.

Western Union provided most of the Telex service in the States.  The 
international carriers providing servce from / to the USA also provided 
limited service in those cities where they had gateway service.  The 
Telex international carriers included RCA Globecom, Western Union 
International (a separate company), ITT and TRT (Tropical Radio 
Telegraph).

Canadawide automatic teleprinter exchange service was introduced by the 
Canadian Pacific and Canadian National Telegraph systems in July 1957. 
This service suplimented the existing international Telex service that 
was put in place in November 1956. Canadian Telex customers could 
connect with nineteen European countries in addition to eighteen Latin 
American, African, and trans-Pacific countries. The major exchanges 
were located in Montreal (01), Toronto(02), Winnepeg(03).

In 1958, Western Union Telegraph Company started to build a telex 
network in the United States. This telex network started as a satellite 
exchange located in New York City and expanded to a nationwide network. 
Western Union chose Siemens & Halske AG,now Siemens AG, and ITT to 
supply the exchange equipment and provisioned the exchange trunks via 
the Western Union national microwave system. Teleprinter equipment was 
originally provided by Siemens & Halske AG and later by Teletype 
Corporation. Initial direct International Telex service was offered by 
Western Union, via W.U. International, in the summer of 1960 with 
limited service to London and Paris.

In 1962, the major exchanges were located in New York City (1), Chicago 
(2), San Francisco (3), Kansas City (4) and Atlanta (5). The Telex 
network expanded by adding the final parent exchanges cities of Los 
Angeles (6), Dallas (7), Philadelphia (8) and Boston (9) starting in 
1966.

The telex numbering plan, usually a six digit number in the United 
States, was based on the major exchange where the customer's telex 
machine terminated. For example, all telex customers that terminated in 
the New York City exchange were assigned a telex number that started 
with a first digit "1". Further, all Chicago based customers had telex 
numbers that started with a first digit of "2". This numbering plan was 
maintained by Western Union as the telex exchanges proliferated to 
smaller cities in the United States. The Western Union telex network 
was built on three levels of exchanges. The highest level was made up 
of the nine exchange cities previously mentioned. Each of these cities 
had the dual capability of terminating both telex customer lines and 
setting up trunk connections to multiple distant telex exchanges. The 
second level of exchanges, located in large cities such as Buffalo, 
Cleveland, Miami, Newark, Pittsburgh and Seattle, were similar to the 
highest level of exchanges in capability of terminating telex customer 
lines and setting up trunk connections. However, these second level 
exchanges had a smaller customer line capacity and only had trunk 
circuits to regional cities. The third level of exchanges, located in 
small to medium sized cities, could terminate telex customer lines and 
had a single trunk group running to its parent exchange.

Western Union offered connections from Telex to the AT&T TWX system in 
May 1966 via its New York Information Services Computer Center. These 
connections were limited to those TWX machines that were equipped with 
automatic answerback capability per CCITT standard.

Yes Telex was run at 66 WPM (50 baud) per CCITT specs.


Look to the following Western Union Technical Review articles for 
additional information:

C. J Colombo, “Telex in Canada”, Western Union Technical Review, 
January 1958: 21
Phillip R. Easterlin, “Telex in New York”, Western Union Technical 
Review, April 1959: 47 figure 4
Phillip R. Easterlin, “Telex in New York”, Western Union Technical 
Review, April 1959: 45
Phillip R. Easterlin, “Telex in Private Wire Systems”, Western Union 
Technical Review, October 1960:131
James S. Chin and Jan J. Gomerman, “CSR4 Exchange”, Western Union 
Technical Review, July 1966: 142 – 149
Fred W. Smith, “European Teleprinters”, Western Union Technical Review, 
October 1960: 172-174
Fred W. Smith, “A New Line of Light-duty Teleprinters and ASR Sets”, 
Western Union Technical Review, January 1964:18 – 31
T. J. O’Sullivan, “TW 56 Concentrator”, Western Union Technical Review, 
July 1963: 111-112
Phillip R. Easterlin, “Telex in the U. S. A”., Western Union Technical 
Review, January 1962: 2-15
Kenneth M. Jockers, “Planning Western Union Telex”, Western Union 
Technical Review, July 1966: 92-95
Kenneth M. Jockers, “Planning Western Union Telex”, Western Union 
Technical Review, July 1966: 94 figure 2
Sergio Wernikoff, “Information Services Computer Center”, Western Union 
Technical Review, July 1966: 130

73 es DX Russ WA3FRP

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