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1 De Forest, Lee
SUBJECT AREA: Broadcasting, Electronics and information technology, Photography, film and optics, Recording, Telecommunications[br]b. 26 August 1873 Council Bluffs, Iowa, USAd. 30 June 1961 Hollywood, California, USA[br]American electrical engineer and inventor principally known for his invention of the Audion, or triode, vacuum tube; also a pioneer of sound in the cinema.[br]De Forest was born into the family of a Congregational minister that moved to Alabama in 1879 when the father became President of a college for African-Americans; this was a position that led to the family's social ostracism by the white community. By the time he was 13 years old, De Forest was already a keen mechanical inventor, and in 1893, rejecting his father's plan for him to become a clergyman, he entered the Sheffield Scientific School of Yale University. Following his first degree, he went on to study the propagation of electromagnetic waves, gaining a PhD in physics in 1899 for his thesis on the "Reflection of Hertzian Waves from the Ends of Parallel Wires", probably the first US thesis in the field of radio.He then joined the Western Electric Company in Chicago where he helped develop the infant technology of wireless, working his way up from a modest post in the production area to a position in the experimental laboratory. There, working alone after normal working hours, he developed a detector of electromagnetic waves based on an electrolytic device similar to that already invented by Fleming in England. Recognizing his talents, a number of financial backers enabled him to set up his own business in 1902 under the name of De Forest Wireless Telegraphy Company; he was soon demonstrating wireless telegraphy to interested parties and entering into competition with the American Marconi Company.Despite the failure of this company because of fraud by his partners, he continued his experiments; in 1907, by adding a third electrode, a wire mesh, between the anode and cathode of the thermionic diode invented by Fleming in 1904, he was able to produce the amplifying device now known as the triode valve and achieve a sensitivity of radio-signal reception much greater than possible with the passive carborundum and electrolytic detectors hitherto available. Patented under the name Audion, this new vacuum device was soon successfully used for experimental broadcasts of music and speech in New York and Paris. The invention of the Audion has been described as the beginning of the electronic era. Although much development work was required before its full potential was realized, the Audion opened the way to progress in all areas of sound transmission, recording and reproduction. The patent was challenged by Fleming and it was not until 1943 that De Forest's claim was finally recognized.Overcoming the near failure of his new company, the De Forest Radio Telephone Company, as well as unsuccessful charges of fraudulent promotion of the Audion, he continued to exploit the potential of his invention. By 1912 he had used transformer-coupling of several Audion stages to achieve high gain at radio frequencies, making long-distance communication a practical proposition, and had applied positive feedback from the Audion output anode to its input grid to realize a stable transmitter oscillator and modulator. These successes led to prolonged patent litigation with Edwin Armstrong and others, and he eventually sold the manufacturing rights, in retrospect often for a pittance.During the early 1920s De Forest began a fruitful association with T.W.Case, who for around ten years had been working to perfect a moving-picture sound system. De Forest claimed to have had an interest in sound films as early as 1900, and Case now began to supply him with photoelectric cells and primitive sound cameras. He eventually devised a variable-density sound-on-film system utilizing a glow-discharge modulator, the Photion. By 1926 De Forest's Phonofilm had been successfully demonstrated in over fifty theatres and this system became the basis of Movietone. Though his ideas were on the right lines, the technology was insufficiently developed and it was left to others to produce a system acceptable to the film industry. However, De Forest had played a key role in transforming the nature of the film industry; within a space of five years the production of silent films had all but ceased.In the following decade De Forest applied the Audion to the development of medical diathermy. Finally, after spending most of his working life as an independent inventor and entrepreneur, he worked for a time during the Second World War at the Bell Telephone Laboratories on military applications of electronics.[br]Principal Honours and DistinctionsInstitute of Electronic and Radio Engineers Medal of Honour 1922. President, Institute of Electronic and Radio Engineers 1930. Institute of Electrical and Electronics Engineers Edison Medal 1946.Bibliography1904, "Electrolytic detectors", Electrician 54:94 (describes the electrolytic detector). 1907, US patent no. 841,387 (the Audion).1950, Father of Radio, Chicago: WIlcox \& Follett (autobiography).De Forest gave his own account of the development of his sound-on-film system in a series of articles: 1923. "The Phonofilm", Transactions of the Society of Motion Picture Engineers 16 (May): 61–75; 1924. "Phonofilm progress", Transactions of the Society of Motion Picture Engineers 20:17–19; 1927, "Recent developments in the Phonofilm", Transactions of the Society of Motion Picture Engineers 27:64–76; 1941, "Pioneering in talking pictures", Journal of the Society of Motion Picture Engineers 36 (January): 41–9.Further ReadingG.Carneal, 1930, A Conqueror of Space (biography).I.Levine, 1964, Electronics Pioneer, Lee De Forest (biography).E.I.Sponable, 1947, "Historical development of sound films", Journal of the Society of Motion Picture Engineers 48 (April): 275–303 (an authoritative account of De Forest's sound-film work, by Case's assistant).W.R.McLaurin, 1949, Invention and Innovation in the Radio Industry.C.F.Booth, 1955, "Fleming and De Forest. An appreciation", in Thermionic Valves 1904– 1954, IEE.V.J.Phillips, 1980, Early Radio Detectors, London: Peter Peregrinus.KF / JW -
2 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 -
3 Eccles, William Henry
[br]b. 23 August 1875 Ulverston, Cumbria, Englandd. 27 April 1966 Oxford, England[br]English physicist who made important contributions to the development of radio communications.[br]After early education at home and at private school, Eccles won a scholarship to the Royal College of Science (now Imperial College), London, where he gained a First Class BSc in physics in 1898. He then worked as a demonstrator at the college and studied coherers, for which he obtained a DSc in 1901. Increasingly interested in electrical engineering, he joined the Marconi Company in 1899 to work on oscillators at the Poole experimental radio station, but in 1904 he returned to academic life as Professor of Mathematics and Physics and Department Head at South West Polytechnic, Chelsea. There he discovered ways of using the negative resistance of galena-crystal detectors to generate oscillations and gave a mathematical description of the operation of the triode valve. In 1910 he became Reader in Engineering at University College, London, where he published a paper explaining the reflection of radio waves by the ionosphere and designed a 60 MHz short-wave transmitter. From 1916 to 1926 he was Professor of Applied Physics and Electrical Engineering at the Finsbury City \& Guilds College and a private consulting engineer. During the First World War he was a military scientific adviser and Secretary to the Joint Board of Scientific Societies. After the war he made many contributions to electronic-circuit development, many of them (including the Eccles-Jordan "flip-flop" patented in 1918 and used in binary counters) in conjunction with F.W.Jordan, about whom little seems to be known. Illness forced Eccles's premature academic retirement in 1926, but he remained active as a consultant for many years.[br]Principal Honours and DistinctionsFRS 1921. President, Institution of Electrical Engineers, 1926–7. President, Physical Society 1929. President, Radio Society of Great Britain.Bibliography1912, "On the diurnal variation of the electric waves occurring in nature and on the propagation of electric waves round the bend of the earth", Proceedings of the Royal Society 87:79. 1919, with F.W.Jordan, "Method of using two triode valves in parallel for generating oscillations", Electrician 299:3.1915, Handbook of Wireless Telegraphy.1921, Continuous Wave Wireless Telegraphy.Further Reading1971, "William Henry Eccles, 1875–1966", Biographical Memoirs of the Royal Society, London, 17.KF
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