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1 Chappe, Claude
SUBJECT AREA: Telecommunications[br]b. 25 December 1763 Brulon, Franced. 23 January 1805 Paris, France[br]French engineer who invented the semaphore visual telegraph.[br]Chappe began his studies at the Collège de Joyeuse, Rouen, and completed them at La Flèche. He was educated for the church with the intention of becoming an Abbé Commendataire, but this title did not in fact require him to perform any religious duties. He became interested in natural science and amongst other activities he carried out experiments with electrically charged soap bubbles.When the bénéfice was suppressed in 1781 he returned home and began to devise a system of telegraphic communication. With the help of his three brothers, particularly Abraham, and using an old idea, in 1790 he made a visual telegraph with suspended pendulums to relay coded messages over a distance of half a kilometre. Despite public suspicion and opposition, he presented the idea to the Assemblée Nationale on 22 May 1792. No doubt due to the influence of his brother, Ignace, a member of the Assemblée Nationale, the idea was favourably received, and on 1 April 1793 it was referred to the National Convention as being of military importance. As a result, Chappe was given the title of Telegraphy Engineer and commissioned to construct a semaphore (Gk. bearing a sign) link between Paris and Lille, a distance of some 240 km (150 miles), using twenty-two towers. Each station contained two telescopes for observing the adjacent towers, and each semaphore consisted of a central beam supporting two arms, whose positions gave nearly two hundred possible arrangements. Hence, by using a code book as a form of lookup table, Chappe was able to devise a code of over 8,000 words. The success of the system for communication during subsequent military conflicts resulted in him being commissioned to extend it with further links, a work that was continued by his brothers after his suicide during a period of illness and depression. Providing as it did an effective message speed of several thousand kilometres per hour, the system remained in use until the mid-nineteenth century, by which time the electric telegraph had become well established.[br]Further ReadingR.Appleyard, 1930, Pioneers of Electrical Communication.International Telecommunications Union, 1965, From Semaphore to Satellite, Geneva.See also: Morse, Samuel Finley BreezeKF -
2 Hertz, Heinrich Rudolph
[br]b. 22 February 1857 Hamburg, Germanyd. 1 January 1894 Bonn, Germany[br]German physicist who was reputedly the first person to transmit and receive radio waves.[br]At the age of 17 Hertz entered the Gelehrtenschule of the Johaneums in Hamburg, but he left the following year to obtain practical experience for a year with a firm of engineers in Frankfurt am Main. He then spent six months at the Dresden Technical High School, followed by year of military service in Berlin. At this point he decided to switch from engineering to physics, and after a year in Munich he studied physics under Helmholtz at the University of Berlin, gaining his PhD with high honours in 1880. From 1883 to 1885 he was a privat-dozent at Kiel, during which time he studied the electromagnetic theory of James Clerk Maxwell. In 1885 he succeeded to the Chair in Physics at Karlsruhe Technical High School. There, in 1887, he constructed a rudimentary transmitter consisting of two 30 cm (12 in.) rods with metal balls separated by a 7.5 mm (0.3 in.) gap at the inner ends and metallic plates at the outer ends, the whole assembly being mounted at the focus of a large parabolic metal mirror and the two rods being connected to an induction coil. At the other side of his laboratory he placed a 70 cm (27½ in.) diameter wire loop with a similar air gap at the focus of a second metal mirror. When the induction coil was made to create a spark across the transmitter air gap, he found that a spark also occurred at the "receiver". By a series of experiments he was not only able to show that the invisible waves travelled in straight lines and were reflected by the parabolic mirrors, but also that the vibrations could be refracted like visible light and had a similar wavelength. By this first transmission and reception of radio waves he thus confirmed the theoretical predictions made by Maxwell some twenty years earlier. It was probably in his experiments with this apparatus in 1887 that Hertz also observed that the voltage at which a spark was able to jump a gap was significantly reduced by the presence of ultraviolet light. This so-called photoelectric effect was subsequently placed on a theoretical basis by Albert Einstein in 1905. In 1889 he became Professor of Physics at the University of Bonn, where he continued to investigate the nature of electric discharges in gases at low pressure until his death after a long and painful illness. In recognition of his measurement of radio and other waves, the international unit of frequency of an oscillatory wave, the cycle per second, is now universally known as the Hertz.[br]Principal Honours and DistinctionsRoyal Society Rumford Medal 1890.BibliographyMuch of Hertz's work, including his 1890 paper "On the fundamental equations of electrodynamics for bodies at rest", is recorded in three collections of his papers which are available in English translations by D.E.Jones et al., namely Electric Waves (1893), Miscellaneous Papers (1896) and Principles of Mechanics (1899).Further ReadingJ.G.O'Hara and W.Pricha, 1987, Hertz and the Maxwellians, London: Peter Peregrinus. J.Hertz, 1977, Heinrich Hertz, Memoirs, Letters and Diaries, San Francisco: San Francisco Press.R.Appleyard, 1930, Pioneers of Electrical Communication.See also: Heaviside, OliverKFBiographical history of technology > Hertz, Heinrich Rudolph
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3 Preece, Sir William Henry
[br]b. 15 February 1834 Bryn Helen, Gwynedd, Walesd. 6 November 1913 Penrhos, Gwynedd, Wales[br]Welsh electrical engineer who greatly furthered the development and use of wireless telegraphy and the telephone in Britain, dominating British Post Office engineering during the last two decades of the nineteenth century.[br]After education at King's College, London, in 1852 Preece entered the office of Edwin Clark with the intention of becoming a civil engineer, but graduate studies at the Royal Institution under Faraday fired his enthusiasm for things electrical. His earliest work, as connected with telegraphy and in particular its application for securing the safe working of railways; in 1853 he obtained an appointment with the Electric and National Telegraph Company. In 1856 he became Superintendent of that company's southern district, but four years later he moved to telegraph work with the London and South West Railway. From 1858 to 1862 he was also Engineer to the Channel Islands Telegraph Company. When the various telegraph companies in Britain were transferred to the State in 1870, Preece became a Divisional Engineer in the General Post Office (GPO). Promotion followed in 1877, when he was appointed Chief Electrician to the Post Office. One of the first specimens of Bell's telephone was brought to England by Preece and exhibited at the British Association meeting in 1877. From 1892 to 1899 he served as Engineer-in-Chief to the Post Office. During this time he made a number of important contributions to telegraphy, including the use of water as part of telegraph circuits across the Solent (1882) and the Bristol Channel (1888). He also discovered the existence of inductive effects between parallel wires, and with Fleming showed that a current (thermionic) flowed between the hot filament and a cold conductor in an incandescent lamp.Preece was distinguished by his administrative ability, some scientific insight, considerable engineering intuition and immense energy. He held erroneous views about telephone transmission and, not accepting the work of Oliver Heaviside, made many errors when planning trunk circuits. Prior to the successful use of Hertzian waves for wireless communication Preece carried out experiments, often on a large scale, in attempts at wireless communication by inductive methods. These became of historic interest only when the work of Maxwell and Hertz was developed by Guglielmo Marconi. It is to Preece that credit should be given for encouraging Marconi in 1896 and collaborating with him in his early experimental work on radio telegraphy.While still employed by the Post Office, Preece contributed to the development of numerous early public electricity schemes, acting as Consultant and often supervising their construction. At Worcester he was responsible for Britain's largest nineteenth-century public hydro-electric station. He received a knighthood on his retirement in 1899, after which he continued his consulting practice in association with his two sons and Major Philip Cardew. Preece contributed some 136 papers and printed lectures to scientific journals, ninety-nine during the period 1877 to 1894.[br]Principal Honours and DistinctionsCB 1894. Knighted (KCB) 1899. FRS 1881. President, Society of Telegraph Engineers, 1880. President, Institution of Electrical Engineers 1880, 1893. President, Institution of Civil Engineers 1898–9. Chairman, Royal Society of Arts 1901–2.BibliographyPreece produced numerous papers on telegraphy and telephony that were presented as Royal Institution Lectures (see Royal Institution Library of Science, 1974) or as British Association reports.1862–3, "Railway telegraphs and the application of electricity to the signaling and working of trains", Proceedings of the ICE 22:167–93.Eleven editions of Telegraphy (with J.Sivewright), London, 1870, were published by 1895.1883, "Molecular radiation in incandescent lamps", Proceedings of the Physical Society 5: 283.1885. "Molecular shadows in incandescent lamps". Proceedings of the Physical Society 7: 178.1886. "Electric induction between wires and wires", British Association Report. 1889, with J.Maier, The Telephone.1894, "Electric signalling without wires", RSA Journal.1898, "Aetheric telegraphy", Proceedings of the Institution of Electrical Engineers.Further ReadingJ.J.Fahie, 1899, History of Wireless Telegraphy 1838–1899, Edinburgh: Blackwood. E.Hawkes, 1927, Pioneers of Wireless, London: Methuen.E.C.Baker, 1976, Sir William Preece, F.R.S. Victorian Engineer Extraordinary, London (a detailed biography with an appended list of his patents, principal lectures and publications).D.G.Tucker, 1981–2, "Sir William Preece (1834–1913)", Transactions of the Newcomen Society 53:119–36 (a critical review with a summary of his consultancies).GW / KFBiographical history of technology > Preece, Sir William Henry
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4 Fessenden, Reginald Aubrey
[br]b. 6 October 1866 East Bolton, Quebec, Canadad. 22 July 1932 Bermuda[br]Canadian radio pioneer who made the first known broadcast of speech and music.[br]After initial education at Trinity College School, Port Hope, Ontario, Fessenden studied at Bishops University, Lennoxville, Quebec. When he graduated in 1885, he became Principal of the Whitney Institute in Bermuda, but he left the following year to go to New York in pursuit of his scientific interests. There he met Edison and eventually became Chief Chemist at the latter's Laboratory in Orange, New Jersey. In 1890 he moved to the Westinghouse Electric and Manufacturing Company, and two years later he returned to an academic career as Professor of Electrical Engineering, initially at Purdue University, Lafayette, Indiana, and then at the Western University of Pennsylvania, where he worked on wireless communication. From 1900 to 1902 he carried out experiments in wireless telegraphy at the US Weather Bureau, filing several patents relating to wire and liquid thermal detectors, or barretters. Following this he set up the National Electric Signalling Company; under his direction, Alexanderson and other engineers at the General Electric Company developed a high-frequency alternator that enabled him to build the first radiotelephony transmitter at Brant Rock, Massachusetts. This made its initial broadcast of speech and music on 24 December 1906, received by ship's wireless operators several hundred miles away. Soon after this the transmitter was successfully used for two-way wireless telegraphy communication with Scotland. Following this landmark event, Fessenden produced numerous inventions, including a radio compass, an acoustic depth-finder and several submarine signalling devices, a turboelectric drive for battleships and, notably, in 1912 the heterodyne principle used in radio receivers to convert signals to a lower (intermediate) frequency.[br]Principal Honours and DistinctionsInstitute of Electrical and Electronics Engineers Medal of Honour 1921.BibliographyUS patents relating to barretters include nos. 706,740, 706,742 and 706,744 (wire, 1902) and 731,029 (liquid, 1903). His invention of the heterodyne was filed as US patent no. 1,050,441 (1913).Further ReadingHelen M.Fessenden, 1940, Fessenden. Builder of Tomorrow. E.Hawkes, 1927, Pioneers of Wireless, London: Methuen. O.E.Dunlop, 1944, Radio's 100 Men of Science.KFBiographical history of technology > Fessenden, Reginald Aubrey
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5 Alexanderson, Ernst Frederik Werner
[br]b. 25 January 1878 Uppsala, Swedend. ? May 1975 Schenectady, New York, USA[br]Swedish-American electrical engineer and prolific radio and television inventor responsible for developing a high-frequency alternator for generating radio waves.[br]After education in Sweden at the High School and University of Lund and the Royal Institution of Technology in Stockholm, Alexanderson took a postgraduate course at the Berlin-Charlottenburg Engineering College. In 1901 he began work for the Swedish C \& C Electric Company, joining the General Electric Company, Schenectady, New York, the following year. There, in 1906, together with Fessenden, he developed a series of high-power, high-frequency alternators, which had a dramatic effect on radio communications and resulted in the first real radio broadcast. His early interest in television led to working demonstrations in his own home in 1925 and at the General Electric laboratories in 1927, and to the first public demonstration of large-screen (7 ft (2.13 m) diagonal) projection TV in 1930. Another invention of significance was the "amplidyne", a sensitive manufacturing-control system subsequently used during the Second World War for controlling anti-aircraft guns. He also contributed to developments in electric propulsion and radio aerials.He retired from General Electric in 1948, but continued television research as a consultant for the Radio Corporation of America (RCA), filing his 321st patent in 1955.[br]Principal Honours and DistinctionsInstitution of Radio Engineers Medal of Honour 1919. President, IERE 1921. Edison Medal 1944.BibliographyPublications relating to his work in the early days of radio include: "Magnetic properties of iron at frequencies up to 200,000 cycles", Transactions of the American Institute of Electrical Engineers (1911) 30: 2,443."Transatlantic radio communication", Transactions of the American Institute of ElectricalEngineers (1919) 38:1,269.The amplidyne is described in E.Alexanderson, M.Edwards and K.Boura, 1940, "Dynamo-electric amplifier for power control", Transactions of the AmericanInstitution of Electrical Engineers 59:937.Further ReadingE.Hawkes, 1927, Pioneers of Wireless, Methuen (provides an account of Alexanderson's work on radio).J.H.Udelson, 1982, The Great Television Race: A History of the American Television Industry 1925–1941, University of Alabama Press (provides further details of his contribution to the development of television).KFBiographical history of technology > Alexanderson, Ernst Frederik Werner
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6 Smith, Willoughby
[br]b. 16 April 1828 Great Yarmouth, Englandd. 17 July 1891 Eastbourne, England[br]English engineer of submarine telegraph cables who observed that light reduced the resistance of selenium.[br]Smith joined the Gutta Percha Company, London, in 1848 and successfully experimented with the use of gutta-percha, a natural form of latex, for the insulation of conducting wires. As a result, he was made responsible for the laying of the first cross-Channel cable between Dover and Calais in 1850. Four years later he laid the first Mediterranean cable between Spezia, Italy, and Corsica and Sardinia, later extending it to Algeria. On its completion he became Manager of the Gutta Percha works, which in 1864 became the Telegraph and Construction Company. In 1865 he assisted on board the Great Eastern with the laying of the transatlantic cable by Bright.Clearly his management responsibilities did not stop him from experimenting practically. In 1866 he discovered that the resistance of a selenium rod was reduced by the action of incident light, an early discovery of the photoelectric effect more explicitly observed by Hertz and subsequently explained by Einstein. In 1883 he read a paper to the Society of Telegraph Engineers (later the Institution of Electrical Engineers), suggesting the possibility of wireless communication with moving trains, an idea that was later successfully taken up by others, and in 1888 he demonstrated the use of water as a practical means of communication with a lighthouse. Four years later, after his death, the system was tried between Alum Bay and the Needles in the Isle of Wight, and it was used subsequently for the Fastnet Rock lighthouse some 10 miles (16 km) off the south-west coast of Ireland.[br]Principal Honours and DistinctionsFounder and Council Member of the Society of Telegraph Engineers 1871; President 1873.BibliographyThe effect of light on the resistance of selenium was reported in a letter to the Vice- Chairman of the Society of Telegraph Engineers on 4 February 1873.7 June 1897, British patent no. 8,159 (the use of water, instead of cable, as a conductor).November 1888, article in Electrician (describes his idea of using water as a conductor, rather than cable).Further ReadingE.Hawkes, 1927, Pioneers of Wireless, London: Methuen.C.T.Bright, 1898, Submarine Cables, Their History, Construction and Working.See also: Field, Cyrus WestKF -
7 Branly, Edouard Eugène
[br]b. 23 October 1844 Amiens, Franced. 24 March 1940 Paris, France[br]French electrical engineer, who c.1890 invented the coherer for detecting radio waves.[br]Branly received his education at the Lycée de Saint Quentin in the Département de l'Aisne and at the Henri IV College of Paris University, where he became a Fellow of the University, graduating as a Doctor of Physics in 1873. That year he was appointed a professor at the College of Bourges and Director of Physics Instruction at the Sorbonne. Three years later he moved to the Free School in Paris as Professor of Advanced Studies. In addition to these responsibilities, he qualified as an MD in 1882 and practised medicine from 1896 to 1916. Whilst carrying out experiments with Hertzian (radio) waves in 1890, Branly discovered that a tube of iron filings connected to a source of direct voltage only became conductive when the radio waves were present. This early form of rectifier, which he called a coherer and which needed regular tapping to maintain its response, was used to operate a relay when the waves were turned on and off by Morse signals, thus providing the first practical radio communication.[br]Principal Honours and DistinctionsPapal Order of Commander of St George 1899. Légion d'honneur, Chevalier 1900, Commandeur 1925. Osiris Prize (jointly with Marie Curie) 1903. Argenteuil Prize and Associate of the Royal Belgian Academy 1910. Member of the Academy of Science 1911. State Funeral at Notre Dame Cathedral.BibliographyAmongst his publications in Comptes rendus were "Conductivity of mediocre conductors", "Conductivity of gases", "Telegraphic conduction without wires" and "Conductivity of imperfect conductors realised at a distance by wireless by spark discharge of a capacitor".Further ReadingE.Hawkes, 1927, Pioneers of Wireless, London: Methuen. E.Larien, 1971, A History of Invention, London: Victor Gollancz.V.J.Phillips: 1980, Early Radio Wave Detectors, London: Peter Peregrinus.KF
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