telegraph


telegraph
telegrapher /teuh leg"reuh feuhr/; esp. Brit., telegraphist, n.
/tel"i graf', -grahf'/, n.
1. an apparatus, system, or process for transmitting messages or signals to a distant place, esp. by means of an electric device consisting essentially of a sending instrument and a distant receiving instrument connected by a conducting wire or other communications channel.
2. Naut. an apparatus, usually mechanical, for transmitting and receiving orders between the bridge of a ship and the engine room or some other part of the engineering department.
3. a telegraphic message.
v.t.
4. to transmit or send (a message) by telegraph.
5. to send a message to (a person) by telegraph.
6. Informal. to divulge or indicate unwittingly (one's intention, next offensive move, etc.), as to an opponent or to an audience; broadcast: The fighter telegraphed his punch and his opponent was able to parry it. If you act nervous too early in the scene, you'll telegraph the character's guilt.
v.i.
7. to send a message by telegraph.
[ < F télégraphe (1792) a kind of manual signaling device; see TELE-1, -GRAPH]

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Electromagnetic communication device.

In 1832 Samuel F.B. Morse made sketches of ideas for a system of electric telegraphy, and in 1835 he developed a code to represent letters and numbers (Morse code). In 1837 he was granted a patent on an electromagnetic telegraph that transmitted signals along a wire. That same year British inventors patented a telegraph system that activated five needle pointers that could be made to point to specific letters and numbers on their mounting plate. Public use of Morse's telegraph system began in 1844 and lasted more than 100 years. By the late 20th century the telegraph had been replaced in most applications in developed countries by digital data transmission systems based on computer technology. See also Western Union Corp.

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Introduction

      any device or system that allows the transmission of information by coded signal over distance. Many telegraphic systems have been used over the centuries, but the term is most often understood to refer to the electric telegraph, which was developed in the mid-19th century and for more than 100 years was the principal means of transmitting printed information by wire or radio wave.

      This article begins with a brief description of notable pre-electric visual telegraph systems and then traces the development of electric telegraphy.

Preelectric telegraph systems
      The word telegraph is derived from the Greek words tele, meaning “distant,” and graphein, meaning “to write.” It came into use toward the end of the 18th century to describe an optical semaphore system developed in France. However, many types of telegraphic communication have been employed since before recorded history. The earliest methods of communication at a distance made use of such media as smoke, fire, drums, and reflected rays of the Sun. Visual signals given by flags and torches were used for short-range communication and continued to be utilized well into the 20th century, when the two-flag semaphore system was widely used, particularly by the world's navies.

      Before the development of the electric telegraph, visual systems were used to convey messages over distances by means of variable displays. One of the most successful of the visual telegraphs was the semaphore developed in France by the Chappe (Chappe, Claude) brothers, Claude and Ignace, in 1791. This system consisted of pairs of movable arms mounted at the ends of a crossbeam on hilltop towers. Each arm of the semaphore could assume seven angular positions 45° apart, and the horizontal beam could tilt 45° clockwise or counterclockwise. In this manner it was possible to represent numbers and the letters of the alphabet. Chains of these towers were built to permit transmission over long distances. The towers were spaced at intervals of 5 to 10 kilometres (3 to 6 miles), and a signaling rate of three symbols per minute could be achieved.

      Another widely used visual telegraph was developed in 1795 by George Murray in England. In Murray's device, characters were sent by opening and closing various combinations of six shutters. This system rapidly caught on in England and in the United States, where a number of sites bearing the name Telegraph Hill or Signal Hill can still be found, particularly in coastal regions. Visual telegraphs were completely replaced by the electric telegraph by the middle of the 19th century.

The beginning of electric telegraphy

The first transmitters and receivers
      The electric telegraph did not burst suddenly upon the scene but rather resulted from a scientific evolution that had been taking place since the 18th century in the field of electricity. One of the key developments was the invention of the voltaic cell in 1800 by Alessandro Volta of Italy. This made it possible to power electric devices in a more effective manner using relatively low voltages and high currents. Previous methods of producing electricity employed frictional generation of static electricity, which led to high voltages and low currents. Many devices incorporating high-voltage static electricity and various detectors such as pith balls and sparks were proposed for use in telegraphic systems. All were unsuccessful, however, because the severe losses in the transmission wires, particularly in bad weather, limited reliable operation to relatively short distances. Application of the battery to telegraphy was made possible by several further developments in the new science of electromagnetism. In 1820 Hans Christian Ørsted (Ørsted, Hans Christian) of Denmark discovered that a magnetic needle could be deflected by a wire carrying an electric current. In 1825 in Britain William Sturgeon (Sturgeon, William) discovered the multiturn electromagnet, and in 1831 Michael Faraday (Faraday, Michael) of Britain and Joseph Henry (Henry, Joseph) of the United States refined the science of electromagnetism sufficiently to make it possible to design practical electromagnetic devices.

      The first two practical electric telegraphs appeared at almost the same time. In 1837 the British inventors Sir William Fothergill Cooke (Cooke, Sir William Fothergill) and Sir Charles Wheatstone (Wheatstone, Sir Charles) obtained a patent on a telegraph system that employed six wires and actuated five needle pointers attached to five galvanoscopes at the receiver. If currents were sent through the proper wires, the needles could be made to point to specific letters and numbers on their mounting plate.

      In 1832 Samuel F.B. Morse, a professor of painting and sculpture at the University of the City of New York (later New York University), became interested in the possibility of electric telegraphy and made sketches of ideas for such a system. In 1835 he devised a system of dots and dashes to represent letters and numbers. In 1837 he was granted a patent on an electromagnetic telegraph. Morse's original transmitter incorporated a device called a portarule, which employed molded type with built-in dots and dashes. The type could be moved through a mechanism in such a manner that the dots and dashes would make and break the contact between the battery and the wire to the receiver. The receiver, or register, embossed the dots and dashes on an unwinding strip of paper that passed under a stylus. The stylus was actuated by an electromagnet turned on and off by the signals from the transmitter.

      Morse had formed a partnership with Alfred Vail (Vail, Alfred Lewis), who was a clever mechanic and is credited with many contributions to the Morse system. Among them are the replacement of the portarule transmitter by a simple make-and-break key, the refinement of the Morse Code so that the shortest code sequences were assigned to the most frequently occurring letters, and the improvement of the mechanical design of all the system components. The first demonstration of the system by Morse was conducted for his friends at his workplace in 1837. In 1843 Morse obtained financial support from the U.S (United States). government to build a demonstration telegraph system 60 kilometres (35 miles) long between Washington, D.C., and Baltimore, Md. Wires were attached by glass insulators to poles alongside a railroad. The system was completed and public use initiated on May 24, 1844, with transmission of the message, “What hath God wrought!” This inaugurated the telegraph era in the United States, which was to last more than 100 years.

Development of the telegraph industry
      Although railroad traffic control was one of the earliest applications of the telegraph, it immediately became a vital tool for the transmission of news around the country. In 1848 the Associated Press was formed in the United States to pool telegraph expenses, and in 1849 Paul Julius Reuters (Reuter, Paul Julius, Baron von) in Paris initiated telegraphic press service (using pigeons to cover sections where lines were incomplete). By 1851 more than 50 telegraph companies were in operation in the United States. One of the most significant was the New York and Mississippi Printing Telegraph Company formed by Hiram Sibley, which was soon consolidated with a number of other start-up telegraph companies into the Western Union Telegraph Company (Western Union Corporation) in 1856. Western Union became the dominant telegraph company in the United States. In 1861 it completed the first transcontinental telegraph line, connecting San Francisco to the Midwest and then on to the East Coast. After the Union Pacific Railroad was finished in 1869, much of the line was relocated to run along the railroad right-of-way to facilitate maintenance.

      In Britain (United Kingdom) the Electric Telegraph Company was formed in 1845 to promote development of the needle telegraph system. As in the United States, development of the telegraph was carried out by highly competitive private companies, but a movement toward monopoly was strong. In 1870 the telegraph industry was nationalized and became part of the British Post Office.

      Because of worldwide interest in applications of the telegraph, the International Telegraph Union was formed in 1865 to establish standards for use in international communication. In the following year the first successful transatlantic cables were completed.

Advances in telegraph technology

Signal processing and transmission
      Soon after its introduction in Europe it became apparent that the American Morse Code was inadequate for the transmission of much non-English text because it lacked letters with diacritical marks. A variant that ultimately became known as the International Morse Code was adopted in 1851 for use on cables, for land telegraph lines except in North America, and later for wireless telegraphy. Except for some minor improvements in 1938, the International Morse Code remained unchanged and is still used for radio communications.

      New technology and devices kept appearing and led to a continual evolution of the telegraph industry during the latter half of the 19th century and the first half of the 20th century. By 1856 the register in the Morse system was replaced by a sounder, and the code was transcribed directly from the sounds by the operator. In 1871 J.B. Stearns of the United States completed refinement of the duplex transmission system originated in Germany by Wilhelm Gintl, which allowed the same line to be used simultaneously for sending and receiving, thus doubling its capacity. This system was further improved by the American inventor Thomas Alva Edison (Edison, Thomas Alva), who patented a quadraplex telegraph system in 1874 that permitted the simultaneous transmission of two signals in each direction on a single line. A major new concept was introduced in 1871 by Jean-Maurice-Émile Baudot (Baudot, Jean-Maurice-Émile) in France. Baudot devised a system for multiplexing (switching) a single line among a number of simultaneous users. The heart of the system was a distributor consisting of a stationary face plate containing concentric circular copper rings that were swept by brushes mounted on a rotating assembly. The face plate was divided into sectors depending on the number of users. Each sector could produce a sequence of five on or off connections that represented a transmitted letter or symbol. The on/off connections were referred to as marks or spaces—in modern terminology, binary digits, or bits (bit), consisting of ones or zeros—and the 32 possible symbols that they encoded came to be known as the Baudot Code. In the Baudot system, the transmitter and receiver had to be operated in synchrony so that the correct transmitter and receiver were connected at the same time. The first systems used manual transmission, but this was soon replaced with perforated tape. Variations of this system were used well into the 20th century; and it was the forerunner of what is now known as time-division multiplexing.

      During this time of rapid change in the telegraph industry a new device, the telephone, was patented by Alexander Graham Bell in 1876. Although the telephone was originally expected to replace the telegraph completely, this turned out not to be the case: both industries thrived side by side for many decades. Much of the technology developed for telephony had parallel applications in telegraphy. A number of systems were developed that allowed simultaneous transmission of telegraph and telephone signals on the same lines. In 1882 the Western Electric Company (Western Electric Company Inc.) was acquired from Western Union by the American Bell Telephone Company. Western Electric had started as a telegraph manufacturing company but later became a major contributor to both the telephone and telegraph industries.

      The vacuum tube (electron tube), patented by Lee De Forest (De Forest, Lee) in the United States in 1907, led to several improvements in telegraph performance and greatly intensified research efforts in telegraphy, telephony, and the emerging field of wireless communication. In 1918 modulated carriers with frequency-division multiplexing, in which several different frequencies are transmitted simultaneously over the same line, were introduced. At the receiving end the different signals were separated from one another by frequency-selective filters and sent to separate decoding units, thus allowing as many as 24 telegraph signals to be transmitted over a single telephone channel. Vacuum tube circuits were used to amplify and regenerate weak signals in a manner not previously possible. The development of new magnetic materials enabled more effective loading of transmission lines, thereby improving transmission speeds. In 1928 loading was first successfully applied to submarine cables (undersea cable) to allow duplex operation, but it was not until 1950 that Western Union installed the first successful underwater vacuum tube repeater.

Printing telegraphs
      In 1903 the British inventor Donald Murray, following the ideas of Baudot, devised a time-division multiplex system for the British Post Office. The transmitter used a typewriter keyboard that punched tape, and the receiver printed text. He modified the Baudot Code by assigning code combinations with the fewest punched holes to the most frequently encountered letters and symbols. Murray sold the patent rights to Western Union and Western Electric in 1912, and this formed the basis of the printing telegraph systems that came into use in the 1920s. (For an earlier experiment in this direction, see BTW: Royal House and the printing telegraph.)

      In 1924 the American Telephone & Telegraph Company (AT&T Corporation) (AT&T) introduced a printing telegraph system called the Teletype (teleprinter), which became widely used for business communication. The unit consisted of a typewriter keyboard and a simplex printer. Each keystroke generated a series of coded electric impulses that were then sent over the transmission line to the receiving system. There the receiver decoded the pulses and printed the message on a paper tape or other medium.

      For many years teleprinters used the five-bit Baudot Code and in some cases other specialized codes. With the advent of computers, however, it became apparent that the Baudot Code was no longer adequate, and in 1966 the American Standard Code for Information Interchange ( ASCII) was established. ASCII consisted of seven bits, compared to five bits for the Baudot Code; these allowed 128 different coded letters or symbols, as compared to 32 for the Baudot Code. Code speeds of 150 words per minute were possible with teleprinter systems using the ASCII code, as compared to 75 words per minute for those using the Baudot Code. (See BTW: ASCII-type printing telegraphs.)

      In 1932 AT&T inaugurated the Teletypewriter Exchange Service (TWX), a switched teleprinter network. Switching was accomplished manually until it was automated after World War II. In Europe a similar service called telex was inaugurated in the early 1930s and was partially automated in Germany before World War II. In 1962 Western Union introduced Telex in the United States as an international teleprinter service, and in 1970 it acquired TWX from AT&T. It was not possible for the Telex and TWX instruments to communicate directly with one another because of differences in transmission codes and transmission speeds. Western Union linked the two services through a network of processing centres that made the necessary conversions between the two systems.

The end of the telegraph era
      After World War II much new technology became available that radically changed the telegraph industry. Old wire lines were too expensive to maintain and were replaced by coaxial cable and microwave links. Very wide-bandwidth channels became available, allowing transmission speeds limited only by the capabilities of the terminal equipment. These new transmission media were later augmented by satellite links and fibre optic transmission lines. In 1974 the Westar satellite, providing enormous capacity for all types of telecommunication, was placed in operation by Western Union. These new transmission channels were complemented by new electronic technology including transistors, integrated circuits, and various microelectronics devices that reduced costs and improved performance. With the advent of the digital computer in the 1960s the trend toward entirely digital communication began.

      The facsimile telegraph was perfected in the 1930s and was widely used for sending photographs and other graphic information over telephone and telegraph lines in an analog transmission system. By the 1980s, however, analog facsimile was virtually replaced by the digital fax machine. In many offices, fax machines have replaced other types of communication, including telegrams, TWX, Telex, and, in many cases, the postal service. In the face of changing technology, the Western Union Telegraph Company was reorganized as the Western Union Corporation in 1988 to handle money transfers and related services. It sold its international private line service to Tele-Columbus AG of Switzerland, the Westar satellite was sold to GM Hughes Electronics Corporation of the United States, and AT&T acquired Western Union's business services group. The telegraph, which started in 1837, had been replaced in most applications in developed countries by digital data transmission systems based on computer technology.

Clare D. McGillem

Additional Reading
George Shiers (ed.), The Electric Telegraph: An Historical Anthology (1977); Lewis Coe, The Telegraph: A History of Morse's Invention and Its Predecessors in the United States (1993); and Paul Israel, From Machine Shop to Industrial Laboratory: Telegraphy and the Changing Context of American Invention, 1830–1920 (1992), detail the development of the telegraph in the United States and Europe and include many excellent illustrations of a wide range of devices and systems related to telegraphy. Robert Luther Thompson, Wiring a Continent: The History of the Telegraph Industry in the United States, 1832–1866 (1947, reissued 1972), describes in detail the industry's formative years and includes copies of Congressional acts and industrial agreements affecting the development of this industry. Brooke Hindle, Emulation and Invention (1981), deals with the evolution of new technology, including Morse's development of the telegraph. Roger L. Freeman, Reference Manual for Telecommunications Engineering, 2nd ed. (1993), is a technical sourcebook containing standards for various types of communication.Clare D. McGillem

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Universalium. 2010.

Synonyms:

Look at other dictionaries:

  • Telegraph [1] — Telegraph (Fernschreiber), Vorrichtung zur Nachrichtenbeförderung, welche den an einem Orte zum sinnlichen Ausdruck gebrachten Gedanken an einem entfernten Orte wahrnehmbar wieder erzeugt, ohne daß der Transport eines Gegenstandes mit der… …   Lexikon der gesamten Technik

  • Telegraph [2] — Telegraph. A. Drahttelegraphie. Die Entwicklung der Drahttelegraphie in den letzten Jahren geht dahin, die Leistungsfähigkeit der Apparate und die Ausnutzung der Leitungen zu steigern. Der alte Morseschreiber wird in Deutschland[763] nach und… …   Lexikon der gesamten Technik

  • Telegraph — Tel e*graph, n. [Gr. ? far, far off (cf. Lith. toli) + graph: cf. F. t[ e]l[ e]graphe. See {Graphic}.] An apparatus, or a process, for communicating intelligence rapidly between distant points, especially by means of preconcerted visible or… …   The Collaborative International Dictionary of English

  • Telegraph [3] — Telegraph. Der Krieg hat einen erheblichen Einfluß auf die Entwicklung des telegraphischen Nachrichtenwesens ausgeübt. Die gesamte in Frage kommende Industrie mußte in erster Linie für Heereszwecke arbeiten; erschwert wurde ihr das dadurch, daß… …   Lexikon der gesamten Technik

  • Telegraph — (Fernschreiber) (telegraph; télégraphe; telegrafo). Man versteht darunter eine Vorrichtung, mit der die an einem Ort zum Ausdruck gebrachten Gedanken an einem andern Ort sofort in für das Auge oder das Ohr verständlichen Zeichen wahrnehmbar… …   Enzyklopädie des Eisenbahnwesens

  • Telegraph — (griech., »Fernschreiber«; hierzu die Tafeln »Telegraphenapparate I u. II« und die »Karte des Welttelegraphennetzes« bei S. 386), jede zur Nachrichtenbeförderung dienende Vorrichtung, durch die der an einem Orte (Senderort) zum sinnlichen… …   Meyers Großes Konversations-Lexikon

  • Telegraph — (vom Griechischen τῆλε, in die Ferne, u. γράφειν, schreiben), eine Vorrichtung od. Maschine zur schnellen Fortpflanzung von Nachrichten in größere Fernen. Das Bedürfniß Nachrichten in größere Fernen, als es durch die menschliche Sprache geschehen …   Pierer's Universal-Lexikon

  • Telegraph — Sm erw. obs. (18. Jh.) Neoklassische Bildung. Entlehnt aus frz. télegraph, das eine neoklassische Bildung aus gr. tẽle und graph ist. Zuerst angewandt auf das 1792 von Chappe entwickelte mechanisch optische Gerät zur Nachrichtenübermittlung, dann …   Etymologisches Wörterbuch der deutschen sprache

  • telegraph — ► NOUN ▪ a system or device for transmitting messages from a distance along a wire, especially one creating signals by making and breaking an electrical connection. ► VERB 1) send a message to by telegraph. 2) send (a message) by telegraph. 3)… …   English terms dictionary

  • Telegraph — Tel e*graph, v. t. [imp. & p. p. {Telegraphed}; p. pr. & vb. n. {Telegraphing}.] [F. t[ e]l[ e]graphier.] To convey or announce by telegraph. [1913 Webster] …   The Collaborative International Dictionary of English

  • telegraph — UK US /ˈtelɪgrɑːf/ noun [U] ► COMMUNICATIONS in the past, the method of sending or receiving messages by electrical or radio signals telegraph verb [I or T] ► »They had telegraphed to say that they had arrived …   Financial and business terms


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