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Terminology

The word "telegraph" was first coined by the French inventor of the Semaphore line, Claude Chappe, who also coined the word "semaphore".[1]

A "telegraph" is a device for transmitting and receiving messages over long distances, i.e., for telegraphy. The word "telegraph" alone now generally refers to an electrical telegraph.

Wireless telegraphy is also known as "CW", for continuous wave (a carrier modulated by on-off keying), as opposed to the earlier radio technique of using a spark gap.[citation needed]

Contrary to the extensive definition used by Chappe, Morse argued that the term telegraph can strictly be applied only to systems that transmit and record messages at a distance. This is to be distinguished from semaphore, which merely transmits messages. Smoke signals, for instance, are to be considered semaphore, not telegraph. According to Morse, telegraph dates only from 1832 when Pavel Schilling invented one of the earliest electrical telegraphs.[2]

A telegraph message sent by an electrical telegraph operator or telegrapher using Morse code (or a printing telegraph operator using plain text) was known as a telegram. A cablegram was a message sent by a submarine telegraph cable,[3] often shortened to a cable or a wire. Later, a Telex was a message sent by a Telex network, a switched network of teleprinters similar to a telephone network.

A wire picture or wire photo was a newspaper picture that was sent from a remote location by a facsimile telegraph. A diplomatic telegram, also known as a diplomatic cable, is the term given to a confidential communication between a diplomatic mission and the foreign ministry of its parent country.[4][5] These continue to be called telegrams or cables regardless of the method used for transmission.

History

Even though early telegraphic precedents, such as signalling through the lighting of pyres, have existed since ancient times, long-distance telegraphy (transmission of complex messages) started in 1792 in the form of semaphore lines, or optical telegraphs, that sent messages to a distant observer through line-of-sight signals. Commercial electrical telegraphs were introduced from 1837.

Optical telegraph

Main articles: Semaphore line and Flag semaphore


Construction schematic of a Prussian optical telegraph (or semaphore) tower, C. 1835

The first telegraphs came in the form of optical telegraph, including the use of smoke signals, beacons, or reflected light, which have existed since ancient times. Early proposals for an optical telegraph system were made to the Royal Society by Robert Hooke in 1684[6] and were first implemented on an experimental level by Sir Richard Lovell Edgeworth in 1767.[7]

The first successful semaphore network was invented by Claude Chappe and operated in France from 1793 to 1846.[8]


Demonstration of the semaphore

During 1790–1795, at the height of the French Revolution, France needed a swift and reliable communication system to thwart the war efforts of its enemies. In 1790, the Chappe brothers set about devising a system of communication that would allow the central government to receive intelligence and to transmit orders in the shortest possible time. On 2 March 1791, at 11 am, they sent the message "si vous réussissez, vous serez bientôt couverts de gloire" (If you succeed, you will soon bask in glory) between Brulon and Parce, a distance of 16 kilometres (9.9 mi). The first means used a combination of black and white panels, clocks, telescopes, and codebooks to send their message.

In 1792, Claude was appointed Ingénieur-Télégraphiste and charged with establishing a line of stations between Paris and Lille, a distance of 230 kilometres (about 143 miles). It was used to carry dispatches for the war between France and Austria. In 1794, it brought news of a French capture of Condé-sur-l'Escaut from the Austrians less than an hour after it occurred.[9]

The Prussian system was put into effect in the 1830s. However, they were highly dependent on good weather and daylight to work and even then could accommodate only about two words per minute. The last commercial semaphore link ceased operation in Sweden in 1880. As of 1895, France still operated coastal commercial semaphore telegraph stations, for ship-to-shore communication.[10]

Electrical telegraphs

Main article: Electrical telegraph


Early developments

Further information: Electrical telegraph § First working systems

The first suggestion for using electricity as a means of communication appeared in the "Scots Magazine" in 1753. Using one wire for each letter of the alphabet, a message could be transmitted by connecting the wire terminals in turn to an electrostatic machine, and observing the deflection of pith balls at the far end.[11] Telegraphs employing electrostatic attraction were the basis of early experiments in electrical telegraphy in Europe but were abandoned as being impractical and were never developed into a useful communication system.

One very early experiment in electrical telegraphy was an electrochemical telegraph created by the German physician, anatomist, and inventor Samuel Thomas von Sömmering in 1809, based on an earlier, less robust design of 1804 by Spanish polymath and scientist Francisco Salva Campillo.[12] Both their designs employed multiple wires (up to 35) in order to visually represent most Latin letters and numerals. Thus, messages could be conveyed electrically up to a few kilometers (in von Sömmering's design), with each of the telegraph receiver's wires immersed in a separate glass tube of acid. As an electric current was applied by the sender representing each digit of a message, it would at the recipient's end electrolyse the acid in its corresponding tube, releasing a stream of hydrogen bubbles next to its associated letter or numeral. The telegraph receiver's operator would visually observe the bubbles and could then record the transmitted message, albeit at a very low baud rate.[12]

The first working telegraph was built by the English inventor Francis Ronalds in 1816 and used static electricity.[13][14] At the family home on Hammersmith Mall, he set up a complete subterranean system in a 175-yard long trench as well as an eight-mile long overhead telegraph. The lines were connected at both ends to clocks marked with the letters of the alphabet and electrical impulses sent along the wire were used to transmit messages. Offering his invention to the Admiralty in July 1816, it was rejected as "wholly unnecessary".[15] His account of the scheme and the possibilities of rapid global communication in Descriptions of an Electrical Telegraph and of some other Electrical Apparatus[16] was the first published work on electric telegraphy and even described the risk of signal retardation due to induction.[17] Elements of Ronalds' design were utilised in the subsequent commercialisation of the telegraph over 20 years later.[18]


Pavel Schilling, an early pioneer of electrical telegraphy

An early electromagnetic telegraph design was created by Russian diplomat Pavel Schilling in 1832.[19] He set it up in his apartment in St. Petersburg and demonstrated the long-distance transmission of signals by positioning two telegraphs of his invention in two different rooms of his apartment. Schilling was the first to put into practice the idea of a binary system of signal transmissions.

Carl Friedrich Gauss and Wilhelm Weber built the first electromagnetic telegraph used for regular communication in 1833 in Göttingen, connecting Göttingen Observatory and the Institute of Physics, covering a distance of about 1 km.[20] The setup consisted of a coil that could be moved up and down over the end of two magnetic steel bars. The resulting induction current was transmitted through two wires to the receiver, consisting of a galvanometer. The direction of the current could be reversed by commuting the two wires in a special switch. Therefore, Gauss and Weber chose to encode the alphabet in a binary code, using positive and negative currents as the two states.

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