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A Teletype Model 32 used for Telex service Telex machine ASR-32.jpg
A Teletype Model 32 used for Telex service

The telex network was a customer-to-customer switched network of teleprinters similar to a telephone network, using telegraph-grade connecting circuits for two-way text-based messages. [1] Telex was a major method of sending written messages electronically between businesses in the post-World War II period. Its usage went into decline as the fax machine grew in popularity in the 1980s.

Teleprinter device for transmitting messages in written form by electrical signals

A teleprinter is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initially they were used in telegraphy, which developed in the late 1830s and 1840s as the first use of electrical engineering. The machines were adapted to provide a user interface to early mainframe computers and minicomputers, sending typed data to the computer and printing the response. Some models could also be used to create punched tape for data storage and to read back such tape for local printing or transmission.

The public switched telephone network (PSTN) is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local telephony operators, providing infrastructure and services for public telecommunication. The PSTN consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all interconnected by switching centers, thus allowing most telephones to communicate with each other. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core network and includes mobile and other networks, as well as fixed telephones.


The "telex" term refers to the network, not the teleprinters; point-to-point teleprinter systems had been in use long before telex exchanges were built in the 1930s. Teleprinters evolved from telegraph systems, and, like the telegraph, they used binary signals, which means that symbols were represented by the presence or absence of a pre-defined level of electric current. This is significantly different from the analog telephone system, which used varying voltages to represent sound. For this reason, telex exchanges were entirely separate from the telephone system, with their own signalling standards, exchanges and system of "telex numbers" (the counterpart of telephone numbers).

Telephone Telecommunications device

A telephone, or phone, is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user.

Telex provided the first common medium for international record communications using standard signalling techniques and operating criteria as specified by the International Telecommunication Union. Customers on any telex exchange could deliver messages to any other, around the world. To lower line usage, telex messages were normally first encoded onto paper tape and then read into the line as quickly as possible. The system normally delivered information at 50 baud or approximately 66 words per minute, encoded using the International Telegraph Alphabet No. 2. In the last days of the telex networks, end-user equipment was often replaced by modems and phone lines, reducing the telex network to what was effectively a directory service running on the phone network.

International Telecommunication Union Specialized agency of the United Nations

The International Telecommunication Union, originally the International Telegraph Union, is a specialized agency of the United Nations that is responsible for issues that concern information and communication technologies. It is the second oldest international organization after the Rhine Navigation Commission (1815).

In telecommunication and electronics, baud is a common measure of symbol rate, one of the components that determine the speed of communication over a data channel.


A late-model British Telecom "Puma" telex machine of the 1980s Puma teleprinter.jpg
A late-model British Telecom "Puma" telex machine of the 1980s

Telex began in Germany as a research and development program in 1926 that became an operational teleprinter service in 1933. The service, operated by the Reichspost (Reich postal service) [2] had a speed of 50 baud — approximately 66 words per minute.

Reichspost was the name of the postal service of Germany from 1866 to 1945.

Telex service spread within Europe and (particularly after 1945) around the world. [3] By 1978, West Germany, including West Berlin, had 123,298 telex connections. Long before automatic telephony became available, most countries, even in central Africa and Asia, had at least a few high-frequency (shortwave) telex links. Often, government postal and telegraph services (PTTs) initiated these radio links. The most common radio standard, CCITT R.44 had error-corrected retransmitting time-division multiplexing of radio channels. Most impoverished PTTs operated their telex-on-radio (TOR) channels non-stop, to get the maximum value from them.

West Germany Federal Republic of Germany in the years 1949–1990

West Germany was the informal name for the Federal Republic of Germany, a country in Central Europe, in the period between its formation on 23 May 1949 and German reunification on 3 October 1990. During this Cold War period, the western portion of Germany was part of the Western Bloc. The Federal Republic was created during the Allied occupation of Germany after World War II, established from eleven states formed in the three Allied zones of occupation held by the United States, the United Kingdom and France. Its (provisional) capital was the city of Bonn. The Cold War era West Germany is unofficially historically designated the Bonn Republic.

West Berlin Political enclave that existed between 1949 and 1990

West Berlin was a political enclave which comprised the western part of Berlin during the years of the Cold War. There was no specific date on which the sectors of Berlin occupied by the Western Allies became "West Berlin", but 1949 is widely accepted as the year in which the name was adopted. West Berlin aligned itself politically with the Federal Republic of Germany and was directly or indirectly represented in its federal institutions.

Africa The second largest and second most-populous continent, mostly in the Northern and Eastern Hemispheres

Africa is the world's second largest and second most-populous continent. At about 30.3 million km2 including adjacent islands, it covers 6% of Earth's total surface area and 20% of its land area. With 1.2 billion people as of 2016, it accounts for about 16% of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, the Isthmus of Suez and the Red Sea to the northeast, the Indian Ocean to the southeast and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It contains 54 fully recognised sovereign states (countries), nine territories and two de facto independent states with limited or no recognition. The majority of the continent and its countries are in the Northern Hemisphere, with a substantial portion and number of countries in the Southern Hemisphere.

The cost of TOR equipment has continued to fall. Although the system initially required specialised equipment, as of 2016 many amateur radio operators operate TOR (also known as RTTY) with special software and inexpensive hardware to connect computer sound cards to short-wave radios. [4]

Amateur radio use of designated radio frequency spectra for purposes of non-commercial exchange of messages

Amateur radio, also known as ham radio, is the use of radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communication. The term "amateur" is used to specify "a duly authorised person interested in radioelectric practice with a purely personal aim and without pecuniary interest;" and to differentiate it from commercial broadcasting, public safety, or professional two-way radio services.


Radioteletype (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link. These machines were superseded by personal computers (PCs) running software to emulate teleprinters. Radioteletype evolved from earlier landline teleprinter operations that began in the mid-1800s. The US Navy Department successfully tested printing telegraphy between an airplane and ground radio station in 1922. Later that year, the Radio Corporation of America successfully tested printing telegraphy via their Chatham, Massachusetts, radio station to the R.M.S. Majestic. Commercial RTTY systems were in active service between San Francisco and Honolulu as early as April 1932 and between San Francisco and New York City by 1934. The US military used radioteletype in the 1930s and expanded this usage during World War II. From the 1980s, teleprinters were replaced by computers running teleprinter emulation software.

Modern cablegrams or telegrams actually operate over dedicated telex networks, using TOR whenever required.[ citation needed ]

Telex served as the forerunner of modern fax, email, and text messaging — both technically and stylistically. Abbreviated English (like "CU L8R" for "see you later") as used in texting originated with telex operators exchanging informal messages in real time[ citation needed ] — they became the first "texters" long before the introduction of mobile phones[ citation needed ]. 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. In this way, a single message could be sent to multiple distant Telex and TWX machines as well as delivering the same message to non-Telex and non-TWX subscribers via Western Union Mailgram.

Operation and applications

Telex messages are routed by addressing them to a telex address, e.g., "14910 ERIC S", where 14910 is the subscriber number, ERIC is an abbreviation for the subscriber's name (in this case Telefonaktiebolaget L.M. Ericsson in Sweden) and S is the country code. Solutions also exist for the automatic routing of messages to different telex terminals within a subscriber organization, by using different terminal identities, e.g., "+T148".

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". At the beginning of the message, the sender would transmit a WRU (Who aRe yoU) 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. The position of the pegs sent an unambiguous identifying code to the sender, so the sender could verify connection to the correct recipient. The WRU code would also be sent at the end of the message, so a correct response would confirm that the connection had remained unbroken during the message transmission. This gave telex a major advantage over group 2 fax, which had no inherent error-checking capability.

The usual method of operation was that the message would be prepared off-line, using paper tape. All common telex machines incorporated a five-hole paper-tape punch and reader. Once the paper tape had been prepared, the message could be transmitted in minimum time. Telex billing was always by connected duration, so minimizing the connected time saved money. 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. The tape would be sent by telex and collected on a corresponding paper tape by the receiver and this tape could then be read into the receiving IT system.

One use of telex circuits, in use until the widescale adoption of X.400 and Internet email, was to facilitate a message handling system, allowing local email systems to exchange messages with other email and telex systems via a central routing operation, or switch. 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. In addition to permitting email to be sent to telex, formal coding conventions adopted in the composition of telex messages enabled automatic routing of telexes to email recipients.

United States

Teletypewriter Exchange Service (TWX)

The Teletypewriter Exchange Service (TWX) was developed by the AT&T Corporation in the United States. It originally transmitted at 45.45 baud or approximately 60 words per minute, using five level Baudot code. AT&T began TWX on November 21, 1931. [5] [6] AT&T later[ when? ] developed a second generation of TWX called "four row" that used the 110 baud, using eight level ASCII code. TWX was offered in both "3-row" Baudot and "4-row" ASCII versions up to the late 1970s.

TWX used the public switched telephone network. In addition to having separate area codes (510, 610, 710, 810, and 910) for the TWX service, the TWX lines were also set up with a special Class of Service to prevent connections from POTS to TWX and vice versa.

The code/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. A TWX customer would place a call to the 10A/B board operator for Baudot – ASCII calls, ASCII – Baudot calls, and also TWX conference calls. The code / speed conversion was done by a Western Electric unit that provided this capability. There were multiple code / speed conversion units at each operator position.

AT&T published the trade magazine TWX , related to the Teletypewriter Exchange Service! from 1944 to 1952. It published articles that touched upon many aspects of the technology.

Western Union purchased the TWX system from AT&T in January 1969. [7] The TWX system and the special US area codes (510, 710, 810, and 910) continued until 1981, when Western Union completed the conversion to the Western Union Telex II system. Any remaining "3-row" Baudot customers were converted to Western Union Telex service during the period 1979 to 1981. Bell Canada retained area code 610 until 1992; its remaining numbers were moved to non-geographic area code 600.

The modem for this service was the Bell 101 dataset, which is the direct ancestor of the Bell 103 modem that launched computer time-sharing. The 101 was revolutionary because it ran on ordinary unconditioned telephone subscriber lines, allowing the Bell System to run TWX along with POTS on a single public switched telephone network.

Telex II was the name for the TWX network after it was acquired from AT&T by Western Union. It was re-acquired by AT&T in 1990 in the purchase of the Western Union assets that became AT&T EasyLink Services.[ citation needed ]

Western Union

In 1958, Western Union started to build a telex network in the United States. [8] 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, [9] now Siemens AG, and ITT [10] to supply the exchange equipment, provisioned the exchange trunks via the Western Union national microwave system and leased the exchange to customer site facilities from the local telephone company. Teleprinter equipment was originally provided by Siemens & Halske AG [11] and later by Teletype Corporation. [12] 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. [13] In 1962, the major exchanges were located in New York City (1), Chicago (2), San Francisco (3), Kansas City (4) and Atlanta (5). [14] 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. [15] 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. [16] The highest level was made up of the nine exchange cities previously mentioned. Each of these cities had the dual capability of terminating 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 connected 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.

Loop signaling was offered in two different configurations for Western Union Telex in the United States. 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, 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.

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. [17] These connections were limited to those TWX machines that were equipped with automatic answerback capability per CCITT standard.

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. In this way, a single message could be sent to multiple distant Telex and TWX machines as well as delivering the same message to non-Telex and non-TWX subscribers via Western Union Mailgram.

International Record Carriers

"International Record Carrier" (IRC) was a term created by the Federal Communications Commission (FCC) in the United States. Bell's original consent agreement limited it to international dial telephony, and the Western Union Telegraph Company had given up its international telegraphic operation in a 1939 bid to monopolize U.S. telegraphy by taking over ITT's Postal, telegraph and telephone service (PTT) business. The result was a de-emphasis on telex in the U.S. and the creation of several international telex and telegraphy companies, collectively called IRCs:

Bell Telex users had to select which IRC to use, and then append the necessary routing digits. The IRCs converted between TWX and Western Union Telegraph Co. standards.

United Kingdom

Telex began in the UK as an evolution from the 1930s Telex Printergram service, appearing in 1932 on a limited basis. This used the telephone network in conjunction with a Teleprinter 7B and signalling equipment to send a message to another subscriber with a Teleprinter, or to the Central Telegraph Office.

In 1945 as the traffic increased it was decided to have a separate network for telex traffic and the first manual exchange opened in London. By 1954, the public inland telex service opened via manually switched exchanges. A number of subscribers were served via automatic sub-centres which used relays and Type 2 uniselectors, acting as concentrators for a manual exchange.

In the late 1950s the decision was made to convert to automatic switching and this was completed by 1961; there were 21 exchanges spread across the country, with one international exchange in London. The equipment used the Strowger system for switching, as was the case for the telephone network. Conversion to Stored Programme Control (SPC) began in 1984 using exchanges made by Canadian Marconi, with the last Strowger exchange closing in 1992. User numbers increased over the following years into the 1990s.

The dominant supplier of the telex machines was Creed, a division of ITT.

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.

British Telecom stopped offering the telex service to new customers in 2004 and discontinued the service in 2008, allowing users to transfer to Swiss Telex if they wished to continue to use telex.


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). This service supplemented 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. [18] The major exchanges were located in Montreal (01), Toronto (02), and Winnipeg (03). [19]


Telex is still in operation but not in the sense described in the CCITT Blue Book documentation. iTelegram offers "telex" without subscriber telex lines. Individual subscribers can use Deskmail, a legacy Windows program that connects to the iTelegram telex network but this is via IP as the last mile. [20] [21] Telex has been mostly superseded by fax, email, and SWIFT, although radiotelex, telex via HF radio, is still used in the maritime industry and is a required element of the Global Maritime Distress and Safety System.

See Worldwide use of telegrams by country for current status in different countries.

See also

Related Research Articles

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Present-day telecommunications in Canada include telephone, radio, television, and internet usage. In the past, telecommunications included telegraphy available through Canadian Pacific and Canadian National.

Electrical telegraph A telegraph is a form of communication in the 1830s

An electrical telegraph was a point-to-point text messaging system, used from the 1840s until better systems became widespread. It used coded pulses of electric current through dedicated wires to transmit information over long distances. It was the first electrical telecommunications system, the most widely used of a number of early messaging systems called telegraphs, devised to send text messages more rapidly than written messages could be sent.

Émile Baudot French engineer

Jean-Maurice-Émile Baudot, French telegraph engineer and inventor of the first means of digital communication Baudot code, was one of the pioneers of telecommunications. He invented a multiplexed printing telegraph system that used his code and allowed multiple transmissions over a single line. The baud unit was named after him.

The People's Republic of China possesses a diversified communications system that links all parts of the country by Internet, telephone, telegraph, radio, and television. The country is served by an extensive system of automatic telephone exchanges connected by modern networks of fiber-optic cable, coaxial cable, microwave radio relay, and a domestic satellite system; cellular telephone service is widely available, expanding rapidly, and includes roaming service to foreign countries. Fiber to the x infrastructure has been expanded rapidly in recent years.

SMS Text messaging service component

SMS is a text messaging service component of most telephone, Internet, and mobile device systems. It uses standardized communication protocols to enable mobile devices to exchange short text messages. An intermediary service can facilitate a text-to-voice conversion to be sent to landlines. SMS was the most widely used data application at the end of 2010, with an estimated 3.5 billion active users, or about 80% of all mobile subscribers.

Telegraphy long distance transmission of textual/symbolic messages without the physical exchange of an object

Telegraphy is the long-distance transmission of textual messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas pigeon post is not. Ancient signalling systems, although sometimes quite extensive and sophisticated as in China, were generally not capable of transmitting arbitrary text messages. Possible messages were fixed and predetermined and such systems are thus not true telegraphs.

The Western Union Company is an American worldwide financial services and communications company. Its headquarters is in Denver, Colorado. Up until it discontinued the service in 2006, Western Union was globally the best-known American company in the business of exchanging telegrams.

A telegraph code is one of the character encodings used to transmit information by telegraphy. Morse code is the most well known such code. Telegraphy usually refers to the electrical telegraph, but telegraph systems using the optical telegraph were in use before that. A code consists of a number of code points, each corresponding to a letter of the alphabet, a numeral, or some other character. In codes intended for machines rather than humans, code points for control characters, such as carriage return, are required to control the operation of the mechanism. Each code point is made up of a number of elements arranged in a unique way for that character. There are usually two types of element, but more element types were employed in some codes not intended for machines. For instance, American Morse code had about five elements, rather than the two of International Morse Code.

Creed & Company

Creed & Company was a British telecommunications company founded by Frederick George Creed which was an important pioneer in the field of teleprinter machines. It was merged into the International Telephone and Telegraph Corporation (ITT) in 1928.

Teletype Model 33 1963—1981 ASCII communications / computer terminal device (keyboard printer paper tape)

The Teletype Model 33 is an electromechanical teleprinter designed for light-duty office. It is less rugged and less expensive than earlier Teletype machines. The Teletype Corporation introduced the Model 33 as a commercial product in 1963 after being originally designed for the US Navy. There are three versions of the Model 33:

Telex may refer to:

Area codes 510 and 341 Area codes covering Oakland and the East Bay of California

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CNCP Telecommunications Former telegraph and data communications (Telex) company.

CNCP Telecommunications was an electrical telegraph operator and later as a telecom company. CNCP was created as a joint venture between the Canadian National Railway and the Canadian Pacific Railway.

Teletype Corporation

The Teletype Corporation, a part of American Telephone and Telegraph Company's Western Electric manufacturing arm since 1930, came into being in 1928 when the Morkrum-Kleinschmidt Company changed its name to the name of its trademark equipment. Teletype Corporation, of Skokie, Illinois, was responsible for the research, development and manufacture of data and record communications equipment, but it is primarily remembered for the manufacture of electromechanical teleprinters.

Plan 55-A

Plan 55-A was one in a series of store and forward message switching systems developed by Western Union and used from 1948 to 1976 for processing telegrams. It is an automated successor to Plan 51, which commenced service in 1951 in a nationwide network of the U.S. Air Force, but required semi-automatic operation.

Donald Murray (inventor) New Zealand engineer

Donald Murray (1865–1945) was an electrical engineer and the inventor of a telegraphic typewriter system using an extended Baudot code that was a direct ancestor of the teleprinter. He can justifiably be called the "Father of the remote Typewriter".

Electrical telegraphy in the United Kingdom History of electrical telegraphy in the United Kingdom

Electrical telegraphy in the United Kingdom led the world in the first half of the nineteenth century. Telegraphy is the sending of textual messages by human operators using symbolic codes. Electrical telegraphy sends these messages over conducting wires, often incorporating a telegram service. It is distinct from the optical telegraphy that preceded it and the radiotelegraphy that followed it. Francis Ronalds first demonstrated a working telegraph over a substantial distance in 1816, but was unable to put it into use. Starting in 1836, William Fothergill Cooke, with the scientific assistance of Charles Wheatstone, developed the first commercial telegraph put into operation anywhere. Important components were the needle telegraph instrument suggested by Wheatstone, the battery invented by John Frederic Daniell, and the relay invented by Edward Davy.


  1. United States. Congress. House. Committee on Interstate and Foreign Commerce (1979). Hearings, Reports and Prints of the House Committee on Interstate and Foreign Commerce. U.S. Government Printing Office. pp. 715–.
  2. "Fifty years of telex". Telecommunication Journal. International Telecommunication Union. 51: 35. 1984. Retrieved 2017-05-18. Just over fifty years ago, in October 1933, the Deutsche Reichspost as it was then known, opened the world's first public teleprinter network.
  3. Roemisch, Rudolf (1978). "Siemens EDS System in Service in Europe and Overseas". Siemens Review. Siemens-Schuckertwerke AG. 45 (4): 176. Retrieved 2016-02-04. The inauguration of the first telex service in the world in Germany in 1933 was soon followed by the development of similar networks in several more European countries. However, telex did not enjoy significant and worldwide growth until after 1945. Thanks to the great advantages of the new telex service, above all in overcoming time differences and language problems, telex networks were introduced in quick succession in all parts of the world.
  4. "RTTY Software". The DXZone.
  5. Anton A. Huurdeman (2003). The worldwide history of telecommunications. Wiley. p. 302. ISBN   978-0-471-20505-0.
  6. "Typing From Afar" (PDF).
  7. "WU to Buy AT&T TWX". Western Union News. II (4). January 15, 1969.
  8. Easterlin, Phillip R. (April 1959). "Telex in New York". Western Union Technical Review: 45. ISSN   0096-6452. OCLC   1769771.
  9. Easterlin, Phillip R. (October 1960). "Telex in Private Wire Systems". Western Union Technical Review: 131.
  10. Chin, James S.; Gomerman, Jan J. (July 1966). "CSR4 Exchange". Western Union Technical Review: 142–9.
  11. Smith, Fred W. (October 1960). "European Teleprinters". Western Union Technical Review: 172–4.
  12. Smith, Fred W. (January 1964). "A New Line of Light-duty Teleprinters and ASR Sets". Western Union Technical Review: 18–31.
  13. O’Sullivan, T.J. (July 1963). "TW 56 Concentrator". Western Union Technical Review: 111–2.
  14. Easterlin, Phillip R. (January 1962). "Telex in the U.S.A.". Western Union Technical Review: 2–15.
  15. Jockers, Kenneth M. (July 1966). "Planning Western Union Telex". Western Union Technical Review: 92–95.
  16. Jockers, Kenneth M. (July 1966). "Planning Western Union Telex". Western Union Technical Review: 94 figure 2.
  17. Wernikoff, Sergio (July 1966). "Information Services Computer Center". Western Union Technical Review: 130.
  18. Colombo, C.J. (January 1958). "Telex in Canada". Western Union Technical Review: 21.
  19. Easterlin, Phillip R. (April 1959). "Telex in New York". Western Union Technical Review: 47 figure 4.
  20. "International Telegram® - Answers to some common questions". 2017. Retrieved 2017-05-18. Western Union closed its telegram service in January, 2006. Western Union is now the fastest way to send money online, and iTelegram is the fastest way to send telegram messages. Western Union's telex/cablegram network, Mailgram® service, and Deskmail/Infomaster services are now a part of International Telegram.
  21. "International Telegram – Send a telegram to Antarctica". 2017. Retrieved 2017-05-18. Delivery: Service by telex / fax / e-mail or INMARSAT terminal (sender must provide number or address).

Further reading