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| Sir John Ambrose Fleming |
Today's Highlight in History-
1904 – English engineer John Ambrose Fleming receives a patent for the thermionic valve (vacuum tube).
In electronics, vacuum tube, electron tube (in North America), tube, or valve (in British English) is a device that controls electric current through a vacuum in a sealed container. Vacuum tubes mostly rely on thermionic emission of electrons from a hot filament or a cathode heated by the filament. This type is called athermionic tube or thermionic valve. A phototube, however, achieves electron emission through the photoelectric effect. Not all electron tubes contain vacuum: gas-filled tubes are devices that rely on the properties of a discharge through an ionized gas.
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| Sir John Ambrose Fleming |
He was born the eldest of seven children of James Fleming DD, a Congregational minister, and his wife, Mary Ann, at Lancaster, Lancashire and baptised on 11 February 1850. He was a devout Christian and helped establish the Evolution Protest Movement. Having no children, he bequeathed much of his estate to Christian charities, especially those that helped the poor. He was an accomplished photographer and, in addition, he painted watercolours and enjoyed climbing in the Alps.
On 11 June 1887 he married Clara Ripley (1856/7–1917), daughter of Walter Freake Pratt, a solicitor from Bath. On 27 July 1928 he married the popular young singer Olive May Franks (b. 1898/9), of Bristol, daughter of George Franks, a Cardiff businessman.
Fleming started school at about the age of ten, attending a private school where he particularly enjoyed geometry. Prior to that his mother tutored him and he had learned, virtually by heart, a book called the Child's Guide to Knowledge, a popular book of the day – even as an adult he would quote from it. His schooling continued at the University College School where, although accomplished at maths, he habitually came bottom of the class at Latin.
Even as a boy he wanted to become an engineer. At 11 he had his own workshop where he built model boats and engines. He even built his own camera, the start of a lifelong interest in photography. Training to become an engineer was beyond the family's financial resources, but he reached his goal via a path that alternated education with paid employment.
He enrolled for a BSc degree at University College, London, graduated in 1870, and studied under the mathematician Augustus de Morgan and the physicist George Carey Foster. He became a student of chemistry at the Royal College of Science in South Kensington in London (now Imperial College). There he first studied Alessandro Volta's battery, which became the subject of his first scientific paper. This was the first paper to be read to the new Physical Society of London (now the Institute of Physics) and appears on page one of volume one of their Proceedings. Financial problems again forced him to work for a living and in the summer of 1874 he became science master at Cheltenham College, a public school, earning £400 per year.
(He later also taught at Rossall School.) His own scientific research continued and he corresponded with James Clerk Maxwell at Cambridge University. After saving £400, and securing a grant of £50 a year, in October 1877 at the age of 27, he once again enrolled as a student, this time at Cambridge. Maxwell's lectures, he admitted, were difficult to follow. Maxwell, he said, often appeared obscure and had "a paradoxical and allusive way of speaking". On occasions Fleming was the only student at those lectures. Fleming again graduated, this time with a First Class Honours degree in chemistry and physics.
He then obtained a DSc from London and served one year at Cambridge University as a demonstrator of mechanical engineering before being appointed as the first Professor of Physics and Mathematics at the University of Nottingham, but he left after less than a year. After leaving the University of Nottingham in 1882, Fleming took up the post of "Electrician" to the Edison Electrical Light Company, advising on lighting systems and the new Ferranti alternating current systems.
In 1884 Fleming joined University College London taking up the Chair of Electrical Technology, the first of its kind in England. Although this offered great opportunities, he recalls in his autobiography that the only equipment provided to him was a blackboard and piece of chalk. In 1897 the Pender Laboratory was foundied at University College, London and Fleming took up the Pender Chair after the £5000 was endowed as a memorial to John Pender, the founder of Cable and Wireless. 1899 Fleming became Scientific Advisor to the Marconi Company and soon after began work on the designing the power plant to enable the Marconi Company to transmit across the Atlantic.
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| Sir John Ambrose Fleming and his invention |
In 1904, as a result of experiments conducted on Edison effect bulbs imported from the USA, he developed a device he called an "oscillation valve" (because it passes current in only one direction). The heated filament, or cathode, was capable of thermionic emission of electrons that would flow to the plate (or anode) when it was at a higher voltage. Electrons, however, could not pass in the reverse direction because the plate was not heated and thus not capable of thermionic emission of electrons.
Later known as the Fleming valve, it could be used as a rectifier of alternating current and as a radio wave detector. This greatly improved the crystal set which rectified the radio signal using an early solid-state diode based on a crystal and a so-called cat's whisker. Unlike modern semiconductors, such a diode required painstaking adjustment of the contact to the crystal in order for it to rectify. The tube was relatively immune to vibration, and thus vastly superior on shipboard duty, particularly for navy ships with the shock of weapon fire commonly knocking the sensitive but delicate galena off its sensitive point (the tube was in general no more sensitive a radio detector, but was adjustment free). The diode tube was a reliable alternative for detecting radio signals. Higher power diode tubes or power rectifiers found their way into power supply applications until they were eventually replaced by silicon rectifiers in the 1960s.
He received a patent on 16 November. however, the Supreme Court of the United States later invalidated the patent because of an improper disclaimer and, additionally, maintained the technology in the patent was known art when filed. This invention is often considered to have been the beginning of electronics, for this was the first vacuum tube. Fleming's diode was used in radio receivers and radars for many decades afterwards, until it was superseded by solid state electronic technology more than 50 years later.
Fleming retired from University College, London in 1927 at the age of 77. He remained active, becoming a committed advocate of the new technology of Television which included serving as the first president of the Television Society.
Fleming also contributed in the fields of photometry, electronics, wireless telegraphy (radio), and electrical measurements. He coined the term Power Factor to describe the true power flowing in an AC power system. He was knighted in 1929, and died at his home in Sidmouth, Devon in 1945. His contributions to electronic communications and radar were of vital importance in winning World War II. Fleming was awarded the IRE Medal of Honor in 1933 for "the conspicuous part he played in introducing physical and engineering principles into the radio art"
Later known as the Fleming valve, it could be used as a rectifier of alternating current and as a radio wave detector. This greatly improved the crystal set which rectified the radio signal using an early solid-state diode based on a crystal and a so-called cat's whisker. Unlike modern semiconductors, such a diode required painstaking adjustment of the contact to the crystal in order for it to rectify. The tube was relatively immune to vibration, and thus vastly superior on shipboard duty, particularly for navy ships with the shock of weapon fire commonly knocking the sensitive but delicate galena off its sensitive point (the tube was in general no more sensitive a radio detector, but was adjustment free). The diode tube was a reliable alternative for detecting radio signals. Higher power diode tubes or power rectifiers found their way into power supply applications until they were eventually replaced by silicon rectifiers in the 1960s.
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| Fleming's first diodes |
He received a patent on 16 November. however, the Supreme Court of the United States later invalidated the patent because of an improper disclaimer and, additionally, maintained the technology in the patent was known art when filed. This invention is often considered to have been the beginning of electronics, for this was the first vacuum tube. Fleming's diode was used in radio receivers and radars for many decades afterwards, until it was superseded by solid state electronic technology more than 50 years later.
Fleming retired from University College, London in 1927 at the age of 77. He remained active, becoming a committed advocate of the new technology of Television which included serving as the first president of the Television Society.
Fleming also contributed in the fields of photometry, electronics, wireless telegraphy (radio), and electrical measurements. He coined the term Power Factor to describe the true power flowing in an AC power system. He was knighted in 1929, and died at his home in Sidmouth, Devon in 1945. His contributions to electronic communications and radar were of vital importance in winning World War II. Fleming was awarded the IRE Medal of Honor in 1933 for "the conspicuous part he played in introducing physical and engineering principles into the radio art"
Fleming was the author of more than a hundred scientific papers and books, including the influential The Principles of Electric Wave Telegraphy (1906) andThe Propagation of Electric Currents in Telephone and Telegraph Conductors(1911).
Today, descendants of the original valve (or vacuum tube) still play an important role in a range of applications. They can be found in the power stages of radio and television transmitters, in musical instrument amplifiers (particularly electric guitar and bass amplifiers), in some high-end audio amplifiers, as detectors of optical and short wavelength radiation, and in sensitive equipment that must be "radiation-hard".
In 1941 the London Power Company commemorated Fleming by naming a new 1,555 GRT coastal collier SS Ambrose Fleming.
On 27 November 2004 a Blue Plaque presented by the Institute of Physics was unveiled at the Norman Lockyer Observatory, Sidmouth, to mark 100 years since the invention of the Thermionic Radio Valve.
Wikipedia
World Events
1849 – A Russian court sentences writer Fyodor Dostoyevsky to death for anti-government activities linked to a radical intellectual group; his sentence is later commuted to hard labor.
1904 – English engineer John Ambrose Fleming receives a patent for the thermionic valve (vacuum tube).
1907 – Indian Territory and Oklahoma Territory join to form Oklahoma, which is admitted as the 46th U.S. state.
1914 – The Federal Reserve Bank of the United States officially opens.
1920 – Qantas, Australia's national airline, is founded as Queensland and Northern Territory Aerial Services Limited.
1940 – World War II: In response to the leveling of Coventry by the German Luftwaffe two days before, the Royal Air Force bombs Hamburg.
1940 – Holocaust: In occupied Poland, the Nazis close off the Warsaw Ghetto from the outside world.
1940 – New York City's "Mad Bomber" George Metesky places his first bomb at a Manhattan office building used by Consolidated Edison.
1943 – World War II: American bombers strike a hydro-electric power facility and heavy water factory in German-controlled Vemork, Norway.
1944 – World War II: Operation Queen, the costly Allied thrust to the Rur, is launched.
1944 – World War II: Dueren, Germany, is destroyed by Allied bombers.
1945 – UNESCO is founded.
1959 – The Sound of Music, a musical by Rodgers and Hammerstein based on The Story of the Trapp Family Singers, opened on Broadwayat the Lunt-Fontanne Theatre.
1965 – Venera program: The Soviet Union launches the Venera 3 space probe toward Venus, which will be the first spacecraft to reach the surface of another planet.
1973 – Skylab program: NASA launches Skylab 4 with a crew of three astronauts from Cape Canaveral, Florida for an 84-day mission.
1973 – U.S. President Richard Nixon signs the Trans-Alaska Pipeline Authorization Act into law, authorizing the construction of the Alaska Pipeline.
1979 – The first line of Bucharest Metro (Line M1) is opened from Timpuri Noi to Semănăto area in Bucharest, Romania.
1988 – The Supreme Soviet of the Estonian Soviet Socialist Republic declares that Estonia is "sovereign" but stops short of declaring independence.
1988 – In the first open election in more than a decade, voters in Pakistan elect populist candidate Benazir Bhutto to be Prime Minister of Pakistan.
1989 – A death squad composed of El Salvadoran army troops kills six Jesuit priests and two others at Jose Simeon Canas University.
1992 – The Hoxne Hoard is discovered by metal detectorist Eric Lawes in Hoxne, Suffolk.
1997 – After nearly 18 years of incarceration, the People's Republic of China releases Wei Jingsheng, a pro-democracy dissident, from jail for medical reasons.
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