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John Ambrose Fleming

John Ambrose Fleming was an electronics pioneer who invented the oscillation valve, or vacuum tube, a device that would help make radios, televisions, telephones and even early electronic computers possible.

John Ambrose Fleming

A brilliant innovator, Fleming was particularly adept at solving technical problems, and at various times in his life he was closely acquainted with James Clerk Maxwell, Thomas Edison and Guglielmo Marconi. It was not easy for Fleming to acquire the education that would enable him to keep such exceptional company. As the eldest of seven children of a minister and his wife, he was chiefly responsible for supporting himself throughout his university years. As a result, his education was interrupted several times while Fleming took different jobs to survive.

Fleming initially enrolled at London’s University College in 1867, having completed most of his earlier education at the University College School, where he showed aptitude in science. He chiefly studied physics and mathematics during his undergraduate years, while working jobs with a Dublin shipbuilder and then as clerk with a London company. He completed his degree in 1870. Though he wanted to attend graduate school, Fleming needed money, so he accepted a position as science master and worked for more than a year before beginning graduate studies at the Royal College of Chemistry. In 1874, Fleming’s education again came to a halt for financial reasons, and he took a job teaching at Cheltenham College until 1877. Afterwards he entered St. John’s College, Cambridge, where James Clerk Maxwell was a professor.

From Maxwell, Fleming received a strong foundation in both electricity and magnetism. He became a social recluse so as to avoid any distractions that could hinder his work. To the disappointment of Fleming and much of the rest of the world, Maxwell died prematurely in 1879 from cancer, preventing him from further contributing to Fleming’s education or to science in general. In 1880, Fleming completed his doctorate and soon after embarked on a career that would have undoubtedly made his former teacher proud.

After a short teaching stint in Nottingham, Fleming was hired as a consultant by the London branches of the Edison Telephone and Electric Light Companies. He remained there a decade, which enabled him to help establish electrical generators and lighting systems in many areas. In 1884, Fleming’s work took him temporarily to America, where he visited Thomas Edison and first received a report of the Edison effect. While investigating blackening that occurred in his light bulbs, Edison had discovered that if an experimental second electrode, or plate, was placed near the filament in a bulb, a small current could be detected in both the plate and the filament, and the former was negative with respect to the latter. At the time the effect was not understood, but Edison patented his plate-containing bulb and Fleming and others sporadically experimented with it over the next several years.

Near the close of the 19th century, Marconi engaged Fleming as a scientific advisor for his telegraphy company, presumably hoping that he could help do for wireless telegraphs what he had done for electric lighting systems. Fleming quickly proved his worth by designing the Poldhu Wireless Station, which became famous soon after its completion for achieving the first wireless transatlantic transmission on December 12, 1901. Despite this success, there were numerous obstacles to be overcome before wireless communication would become practical for widespread use. One of the biggest problems at the time was the lack of adequate signal detection and amplification, especially for high-frequency radio waves. Crystal rectifiers were then used to convert the alternating current produced by radio waves into direct current, but Fleming believed that he could develop a more efficient method. Recalling the Edison effect and now able to explain it (due to J.J. Thomson’s work on the electron) as the flow of electrons from the hot filament to the plate, Fleming developed the first electronic rectifier.

Fleming called his rectifying device, which he adapted from Edison’s patented plate-containing light bulb, an oscillation valve. But it later came to be known by other names, including the Fleming valve, thermionic valve, diode and, especially in the United States, the vacuum tube. Fleming patented the valve, which functioned as both a detector and a rectifier, in 1904: This is often considered the birth of electronics. A few years later, Lee De Forest improved on the vacuum tube by adding a grid of fine wire between the positive and negative electrodes in Fleming’s model. This change allowed greater control of current. Vacuum tubes of this design were used in radios for several decades, as well as for television sets and electronic computers when those technologies appeared. Fleming himself was involved in the budding television industry late in his life, serving as president of the Television Society of London.

In addition to his consulting work, Fleming held academic positions throughout much of his life. He was chair of England’s first university electrical engineering department from its establishment at University College, London, in 1885 until his retirement from that institution in 1926. He is often credited with devising the right-hand rule to help his students, with whom he was quite popular, easily determine the directional relationships between a current, its magnetic field and electromotive force. Fleming was also active with the Physical Society of London, presenting the group’s inaugural address in 1874 and his final address in 1939, when he was 90 years old. For his scientific and engineering achievements, he received many honors and awards, including the Faraday Medal from the Institution of Electrical Engineers, the Gold Medal of the Institute of Radio Engineers, and the Albert Medal from the Royal Society of Arts. Fleming was knighted in 1929 and died, after a remarkably long and productive life, on April 18, 1945.