Telex

Telex is a telecommunication system that allows text-based messages to be sent and received by teleprinter over telephone lines. The term "telex" may refer to the service, the network, the devices, or a message sent using these. Telex emerged in Germany in the 1930s and became a major method of sending text messages electronically between businesses in the post–World War II period. Its usage declined as the fax machine grew in popularity in the 1980s. The technology operates over the circuits of the public switched telephone network or by private lines, using binary signals encoded with the International Telegraph Alphabet No. 2 at a standard speed of 50 baud. Telex provided the first common medium for international record communications using standard signalling techniques as specified by the International Telecommunication Union (ITU). A key feature of telex was the "answerback" system, which allowed senders to confirm with a high degree of certainty that their message had been received by the correct recipient. Telex networks were established in many countries. In the United States, the American Telephone and Telegraph Company developed the Teletypewriter Exchange Service (TWX) beginning in 1931, while Western Union built a separate telex network starting in 1958. The United Kingdom developed its own telex network from the 1930s, with full automatic switching completed by 1961. Canada, New Zealand, Kenya, and many other nations also established telex services, often connecting local subscribers to an international network spanning Europe, Africa, Asia, and the Americas. In the 1980s, the successor to CCITT, ITU-T, developed an enhanced system, Teletex, which only saw limited adoption, although some of the associated standards influenced computer networking protocols such as LDAP. Telex has been largely superseded by fax, email, and systems such as SWIFT, though radiotelex via HF radio remains in use in the maritime industry as...