Fleming valve
Encyclopedia
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
diode
Diode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
invented by John Ambrose Fleming
John Ambrose Fleming
Sir 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 is also famous for the left hand rule...
and used in the earliest days of radio communication. As the first vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
, 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 engineering
Electrical engineering
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...
.
Applications
The Fleming valve was the first practical application of the "Edison effect" (thermionic emissionThermionic emission
Thermionic 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 binding potential, also known as work function of the metal. The charge carriers can be electrons or ions, and...
) discovered in 1883 by Thomas Edison
Thomas Edison
Thomas Alva Edison was an American inventor and businessman. He 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. In addition, he created the world’s first industrial...
shortly after his invention of the incandescent light bulb
Incandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
, 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 London
University College London
University College London is a public research university located in London, United Kingdom and the oldest and largest constituent college of the federal University of 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 Marconi
Guglielmo Marconi
Guglielmo Marconi was an Italian inventor, known as the father of long distance radio transmission and for his development of Marconi's law and a radio telegraph system. Marconi is often credited as the inventor of radio, and indeed he shared the 1909 Nobel Prize in Physics with Karl Ferdinand...
to attempt transmission of radio waves across the Atlantic from Poldhu
Poldhu
Poldhu 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...
, England
England
England 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, with the North Sea to the east and the English Channel to the south separating it from continental...
, to Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends 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 3500 kilometres (2,174.8 mi). 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 galvanometer
Galvanometer
A 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 in a magnetic field. .Galvanometers were...
. 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 galvanometer
Galvanometer
A 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 in a magnetic field. .Galvanometers were...
. 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 AudionAudion tube
The Audion is an electronic amplifying vacuum tube 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 triode
Triode
A 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. The triode vacuum tube was the first electronic amplification device...
, which was then central to the creation of long-distance telephone
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
and radio communications, radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
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. Weagant
Roy Alexander Weagant
Roy 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