Telex
Telex is a telecommunication system that allows text-based messages to be sent and received by teleprinter over telephone lines.
[1] Telex emerged in the 1930s and became a major method of sending text messages electronically between businesses in the post–World War II period.
The system normally delivered information at 50 baud or approximately 66 words per minute, encoded using the International Telegraph Alphabet No.
Long before automatic telephony became available, most countries, even in central Africa and Asia, had at least a few high-frequency shortwave telex links.
[citation needed] Telex served as the forerunner of modern fax, email, and text messaging – both technically and stylistically.
Telex users could send the same message to several places around the world at the same time, like email today, using the Western Union InfoMaster Computer.
This involved transmitting the message via paper tape to the InfoMaster Computer (dial code 6111) and specifying the destination addresses for the single text.
[8] A major advantage of telex is that the receipt of the message by the recipient could be confirmed with a high degree of certainty by the "answerback", which is a transmission-control enquiry character.
code, and the recipient machine would automatically initiate a response which was usually encoded in a rotating drum with pegs, much like a music box.
However, it was also possible to connect in "real-time", where the sender and the recipient could both type on the keyboard and these characters would be immediately printed on the distant machine.
Telex could also be used as a rudimentary but functional carrier of information from one IT system to another, in effect a primitive forerunner of electronic data interchange.
The sending IT system would create an output (e.g., an inventory list) on paper tape using a mutually agreed format.
One of the largest such switches was operated by Royal Dutch Shell as recently as 1994, permitting the exchange of messages between a number of IBM Officevision, Digital Equipment Corporation ALL-IN-1 and Microsoft Mail systems.
By 1962, the network had grown to 100 switchboard locations to handle the traffic, causing considerable delay in the speed of connections of up to 21⁄2 minutes on average.
[9] On August 31, 1962, the service was integrated into the Direct Distance Dialing (DDD) network, which improved connection times to about thirty seconds.
Canada moved its TWX-numbers, as well as Datalink services, to the non-geographic area code 600, effective October 1, 1993, in exchange for returning 610.
The code and speed conversion between 3-row Baudot and 4-row ASCII TWX service was accomplished using a special Bell 10A/B board via a live operator.
[23] The telex network expanded by adding the final parent exchange cities of Los Angeles (6), Dallas (7), Philadelphia (8) and Boston (9), starting in 1966.
This numbering plan was maintained by Western Union as the telex exchanges proliferated to smaller cities in the United States.
However, these second level exchanges had a smaller customer line capacity and only had trunk circuits connected to regional cities.
[26] Western Union offered connections from telex to the AT&T Teletypewriter Exchange (TWX) system in May 1966 via its New York Information Services Computer Center.
USA-based telex users could send the same message to several places around the world at the same time, like email today, using the Western Union InfoMaster Computer.
This involved transmitting the message via paper tape to the InfoMaster Computer (dial code 6111) and specifying the destination addresses for the single text.
International record carrier (IRC) was a term created by the Federal Communications Commission in the United States.
A number of subscribers were served via automatic sub-centres which used relays and Type 2 uniselectors, acting as concentrators for a manual exchange.
A separate service Secure Stream 300 (previously Circuit Switched Data Network) was a variant of telex running at 300 baud, used for telemetry and monitoring purposes by utility companies and banks, among others.
This was a high-security virtual private wire system with a high degree of resilience through diversely routed dual-path network configurations.
[34] Canada-wide automatic teleprinter exchange service was introduced by the CPR Telegraph Company and CN Telegraph in July 1957 (the two companies, operated by rivals Canadian National Railway and Canadian Pacific Railway, would join to form CNCP Telecommunications in 1967).
