telex

telex
Name	Telex
Invented	1930s
Developer	Western Union; Siemens AG; ITT Corporation
Type	Teleprinter network

telex

Telex was a global teleprinter-based switched network for written messaging pioneered in the 1930s and expanded through the mid-20th century. It connected telegraph bureaus, postal services, commercial enterprises and diplomatic missions, enabling interoperability among manufacturers such as Siemens AG, ITT Corporation, Western Union, Bell Telephone Laboratories, General Post Office and Deutsche Bundespost. Major users included United Nations, International Monetary Fund, World Bank, Bloomberg L.P., Reuters, Associated Press, BBC, Deutsche Bahn, Pan American World Airways, and national ministries and central banks.

History

Early experiments with teleprinter switching grew from telegraphy and automated switching developments by Alexander Graham Bell-era firms and later innovators like Rudolf Hell and Émile Baudot. The Baudot code and electromechanical machines such as the Morse-derived telegraphs preceded commercial telex networks developed by Western Union in the United States, Siemens AG in Germany, and the General Post Office in the United Kingdom. During World War II and the Cold War, telex systems were expanded for diplomatic traffic handled via embassies, NATO communication centers and intelligence services; corporations such as IBM and AT&T adapted switching and routing concepts. Postwar reconstruction, the rise of international trade organizations like GATT and institutions including International Chamber of Commerce drove growth. The 1960s and 1970s saw integration with data networks and standards work involving International Telecommunication Union and national postal administrations. The arrival of packet-switched networks such as ARPANET and services from CompuServe and AOL presaged telex’s decline.

Technology and Operation

Telex employed electromechanical teleprinters such as the Teletype Model 33 and systems using serial asynchronous transmission based on character codes like Baudot code and later ASCII. Switching used electromechanical exchanges, crossbar switches inspired by Almon B. Strowger concepts and later electronic switching from Bell Labs and companies like Western Electric. Message routing relied on directory numbering schemes analogous to International Telecommunication Numbering Plan proposals; addressing used subscriber identifiers maintained by national operators such as Deutsche Bundespost and Post Office. Circuit interfaces included direct current (DC) four-wire circuits, rotary dial selectors, and teletypewriter exchange (TWX) trunks offered by AT&T. Error control and line testing were influenced by practices from ITU-T study groups and pioneers such as Claude Shannon whose information theory underpinned signaling reliability improvements.

Network and Infrastructure

National and international telex networks were operated by entities like British Telecom successors, Poste Italiane, La Poste, Deutsche Bundespost, Japan Post, PTT Netherlands and Telefónica. Submarine cable systems, microwave links engineered by RCA Corporation and Marconi Company, and terrestrial leased lines from SITA and Union Internationale des Télécommunications-coordinated carriers formed the backbone. Exchanges used technologies from Siemens AG, FACIT, Gossage, ITT Corporation and ITT Cannon; manufacturing also involved AEG and Northrop Grumman subsidiaries. International gateways were coordinated through treaty frameworks including agreements among Universal Postal Union members and bilateral accords between postal administrations and national telegraph services.

Usage and Applications

Telex served news agencies such as Reuters, Associated Press, Agence France-Presse; financial markets including New York Stock Exchange, London Stock Exchange, Frankfurt Stock Exchange and central banks like Bank of England and Deutsche Bundesbank for market bulletins and instructions. Shipping companies including Maersk, airlines like Pan Am and British Airways, and freight forwarders used telex for manifests and bookings; hotels such as Hilton Worldwide and InterContinental Hotels Group employed telex for reservations. Legal firms, diplomatic services at United States embassies, and international organizations including United Nations bureaus and Olympic Games organizing committees used telex for secure written orders, often routed via secure circuits overseen by agencies like NSA and national security ministries. Journalists from The Times (London), The New York Times, Le Monde, Der Spiegel transmitted copy; corporations including Ford Motor Company, General Motors, Siemens AG and Siemens subsidiaries handled procurement and contracts over telex.

International Standards and Regulation

Standardization was driven by International Telecommunication Union (ITU) study groups, collaboration with the International Organization for Standardization on character sets and machine interfaces, and national postal-telegraph administrations such as Poste Italiane and Deutsche Bundespost. Protocols referenced Baudot code, ITU-T V-series recommendations, and later ASCII mappings; numbering plans and interconnect tariffs were regulated under bilateral treaties and conventions among Universal Postal Union members. Operational practices, message precedence categories (routine, priority, urgent, immediate) and security arrangements were promulgated in coordination with bodies such as International Chamber of Commerce and standards committees involving vendors like Western Union and ITT Corporation.

Decline and Legacy

From the 1980s, telex traffic declined as electronic mail services offered by CompuServe, MCI Communications Corporation, BT Group and internet protocols developed in RFC 821 and related standards displaced store-and-forward teleprinters. Corporate migration to proprietary networks from Bloomberg L.P., Thomson Reuters and financial terminals reduced telex volume. Legacy influences persist in terminology, address conventions and in protocols for secure written messaging in SWIFT and maritime telex derivatives; museums such as the Science Museum, London, Deutsches Museum and archives at Smithsonian Institution preserve machines and records. The telex era shaped early digital communication practices adopted by organizations including European Space Agency, NASA, universities like Massachusetts Institute of Technology, University of Cambridge and ETH Zurich and influenced later developments in voice mail and instant messaging.

Category:Telecommunications