The
Fleming valve, also called the
Fleming oscillation valve, was a
vacuum tubeIn electronics, a vacuum tube, electron tube , thermionic valve, or valve is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space...
diodeIn electronics a diode is a two-terminal electronic component which conducts electric current asymmetrically or unidirectionally; that is, it conducts current more easily in one direction than in the opposite direction. The term usually refers to a semiconductor diode, the most common type today,...
invented by
John Ambrose FlemingSir John Ambrose Fleming was an English electrical engineer and physicist. He is known for inventing the first thermionic valve or vacuum tube, the diode, then called the kenotron in 1904. He also invented the right-hand rule, used in mathematics and electronics...
and used in the earliest days of radio communication. As the first
vacuum tubeIn electronics, a vacuum tube, electron tube , thermionic valve, or valve is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space...
, the IEEE has described it as "one of the most important developments in the history of electronics", and it is on the
List of IEEE Milestones for
electrical engineeringElectrical engineering, sometimes referred to as electrical and electronic engineering, is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after...
.
The Fleming valve was the first practical application of the "Edison effect" (
thermionic emissionThermionic emission is the heat-induced flow of charge carriers from a surface or over a potential-energy barrier. This occurs because the thermal energy given to the carrier overcomes the forces restraining it. The charge carriers can be electrons or ions, and in older literature are sometimes...
) discovered in 1883 by
Thomas EdisonThomas Alva Edison was an American inventor, scientist and businessman who developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb...
shortly after his invention of the
incandescent light bulbThe incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence . An electric current passes through a thin filament, heating it until it produces light...
, that is, the emission of electrons by a lamp's heated filament to a nearby metal plate.
The
Fleming valve, also called the
Fleming oscillation valve, was a
vacuum tubeIn electronics, a vacuum tube, electron tube , thermionic valve, or valve is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space...
diodeIn electronics a diode is a two-terminal electronic component which conducts electric current asymmetrically or unidirectionally; that is, it conducts current more easily in one direction than in the opposite direction. The term usually refers to a semiconductor diode, the most common type today,...
invented by
John Ambrose FlemingSir John Ambrose Fleming was an English electrical engineer and physicist. He is known for inventing the first thermionic valve or vacuum tube, the diode, then called the kenotron in 1904. He also invented the right-hand rule, used in mathematics and electronics...
and used in the earliest days of radio communication. As the first
vacuum tubeIn electronics, a vacuum tube, electron tube , thermionic valve, or valve is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space...
, the IEEE has described it as "one of the most important developments in the history of electronics", and it is on the
List of IEEE Milestones for
electrical engineeringElectrical engineering, sometimes referred to as electrical and electronic engineering, is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after...
.
Applications
The Fleming valve was the first practical application of the "Edison effect" (
thermionic emissionThermionic emission is the heat-induced flow of charge carriers from a surface or over a potential-energy barrier. This occurs because the thermal energy given to the carrier overcomes the forces restraining it. The charge carriers can be electrons or ions, and in older literature are sometimes...
) discovered in 1883 by
Thomas EdisonThomas Alva Edison was an American inventor, scientist and businessman who developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb...
shortly after his invention of the
incandescent light bulbThe incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence . An electric current passes through a thin filament, heating it until it produces light...
, that is, the emission of electrons by a lamp's heated filament to a nearby metal plate. Edison was granted a patent for this device as part of an electrical indicator in 1884, but did not hit upon any practical use. Professor Fleming of
University College LondonUniversity College London is a British university institution and a constituent college of the University of London, based primarily in Bloomsbury, London...
consulted for the Edison Electric Light Company from 1881-1891, and subsequently for the Marconi Wireless Telegraph Company.
In 1901 Fleming designed a transmitter for
Guglielmo MarconiMarchese Guglielmo Marconi was an Italian inventor, best known for his development of a radiotelegraph system, which served as the foundation for the establishment of numerous affiliated companies worldwide...
to attempt transmission of radio waves across the Atlantic from
PoldhuPoldhu is a small area in south Cornwall, England, UK, situated on the Lizard Peninsula it comprises Poldhu Point and Poldhu Cove. It lies on the coast west of Goonhilly Downs, with Mullion to the south and Porthleven to the north...
,
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
, to
Nova ScotiaNova Scotia is a Canadian province located on Canada's southeastern coast. It is the most populous province in Atlantic Canada. Its capital, Halifax, is a major economic centre of the region. Nova Scotia is the second-smallest province in Canada with an area of...
,
CanadaCanada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean...
. The distance between the two points was about 3,500 kilometres (2,100 miles). Although widely heralded as a great scientific advance, there was also some skepticism about this claim, in part because the signals had only been heard faintly and sporadically. In addition, there was no independent confirmation of the reported reception, and the transmission, which merely consisted of the three dots of the Morse code letter
S sent repeatedly, came from a transmitter whose signals were difficult to differentiate from the noise made by atmospheric static discharges. (A detailed technical review of the early transatlantic work appears in John S. Belrose's work of 1995.) The receptions of signals were difficult to detect with a
galvanometerA galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil...
. Fleming researched on a way that he could get the received signal to flow in only one direction, its oscillations could be detected with less trouble.
In 1904 Fleming tried an Edison effect bulb for this purpose, and found that it worked well to rectify high frequency oscillations and thus allow detection of the rectified signals by a
galvanometerA galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil...
. On November 16, 1904, he applied for a US patent for what he termed an oscillation valve. This patent was subsequently issued as number 803,684 and found immediate utility in the detection of messages sent by Morse code.
Oscillation valves
The Fleming valve proved to be the start of a technological revolution. After reading Fleming's 1905 paper on his oscillation valve, American engineer Lee DeForest in 1906 created a three-element vacuum tube (the
AudionThe Audion is an electronic amplifier device invented by Lee De Forest in 1906. It was the forerunner of the triode, in which the current from the filament to the plate was controlled by a third element, the grid...
) by adding a modulation grid. It could act as an amplifier and oscillator as well as detector. De Forest quickly refined his device into the
triodeA triode is an electronic amplification device having three active electrodes. The term most commonly applies to a vacuum tube with three elements: the filament or cathode, the grid, and the plate or anode...
, which was then central to the creation of long-distance
telephoneThe telephone is a telecommunications device that transmits and receives sound, most commonly the human voice. It is one of the most common household appliances in the developed world, and has long been considered indispensable to business, industry and government...
and radio communications,
radarRadar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for RAdio Detection And...
s, and early digital computers. Similarities and differences between the Fleming valve and DeForest's triode caused decades of expensive and disruptive litigation, which were not settled until 1943 when the United States Supreme Court ruled Fleming's patent invalid.
Patents
Issued - Instrument for converting alternating electric currents into continuous currents (Fleming valve patent)
Cited by, Jan 7, 1910 : Fleming valve improvement by
R. A. WeagantRoy Alexander Weagant was a noted Canadian-American radio pioneer.Weagant was born in Morrisburg, Ontario, and at age 4 moved to Derby Line, Vermont...
, Apr 12, 1910 : John Ambrose Fleming patent, Mar 10, 1917 : Fleming valve improvement by R. A. Weagant, Jan 8, 1918 : Fleming valve improvement by R. A. Weagant, Sep 10, 1918 : Fleming valve improvement by R. A. Weagant, Dec 31, 1918 : Fleming valve improvement by R. A. Weagant, Jun 10, 1919 : Fleming valve circuit improvement by R. A. Weagant, May 4, 1920 : Fleming valve improvement by R. A. Weagant, Jul 27, 1920 : Inverter converter by L. W. Chubb, May 31, 1921 : Fleming valve improvement by R. A. Weagant, Jun 15, 1926 : Inverter converter by L. W. Chubb, May 1, 1928 : Fleming valve circuit improvement by P. E. Edelman, Jun 7, 1949 : Electrode improvement by H. L. Ratchford
External links