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{{Short description|Electronic detecting or amplifying vacuum tube}}
{{ [[Image:Triode tube 1906.jpg|thumb|[[Triode]] Audion [[vacuum tube]] from 1908. The [[Hot_cathode#Cathode_heater|filament]] (which was also the cathode) was at the lower left inside the tube, but
The '''Audion''' was an electronic detecting or amplifying [[vacuum tube]]<ref name="Okamura" /> invented by American electrical engineer [[Lee de Forest]] as a [[diode]] in 1906.<ref name="Patent">De Forest patented a number of variations of his detector tubes starting in 1906. The patent that most clearly covers the Audion is {{US patent|879532}}, ''[
▲[[Image:Triode tube 1906.jpg|thumb|Triode Audion from 1908. The filament (which was also the cathode) was at the lower left inside the tube, but the filament has burned out and is no longer present. The filament's connecting and supporting wires are visible. The plate is at the middle top, and the grid is the serpentine electrode below it. The plate and grid connections leave the tube at the right.]]
▲The '''Audion''' was an electronic detecting or amplifying [[vacuum tube]]<ref name="Okamura" /> invented by American electrical engineer [[Lee de Forest]] in 1906.<ref name="Patent">De Forest patented a number of variations of his detector tubes starting in 1906. The patent that most clearly covers the Audion is {{US patent|879532}}, ''[http://www.google.com/patents/US879532 Space Telegraphy]'', filed January 29, 1907, issued February 18, 1908</ref><ref name="De Forest">{{cite journal
▲ | last = De Forest
| first = Lee
| title = The Audion; A New Receiver for Wireless Telegraphy
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| volume = 25
| pages = 735–763
| publisher = American Institute of Electrical and
| date = January 1906
| url = https://babel.hathitrust.org/cgi/pt?id=uiug.30112089533605&view=1up&seq=356
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| access-date = March 30, 2021}} The link is to a reprint of the paper in the ''Scientific American Supplement'', Nos. 1665 and 1666, November 30, 1907 and December 7, 1907, p.348-350 and 354-356.</ref><ref name="Godfrey">{{cite encyclopedia
| last = Godfrey
| first = Donald G.
| title = Audion
| encyclopedia = Historical Dictionary of American Radio
| pages = 28
| publisher = Greenwood Publishing Group
| year = 1998
| isbn = 9780313296369
| url = https://books.google.com/books?id=4l_2kkv5aeMC&q=%22Audion&pg=PA28
| access-date = January 7, 2013}}</ref><ref name="IA-SA-reprint">{{cite journal |last1=de Forest |first1=Lee |title=The Audion - A new receiver for wireless telegraphy |journal=Scientific American |date=30 Nov 1907 |volume=64 |issue=1665 |pages=348-352 |url=https://archive.org/details/sim_scientific-american-supplement_1907-11-30_64_1665/page/348/mode/1up |access-date=21 October 2023}} Non-paywalled reprint of the DeForest presentation at the October 26, 1906 New York meeting of the AIEE. Text version available at the [https://www.earlyradiohistory.us/1907aud.htm Early Radio History] site.</ref> Improved, it was patented as the first [[triode]] in 1908,<ref name="Okamura">{{cite book
| last = Okamura
| first = Sōgo
| title = History of Electron Tubes
| publisher = IOS Press
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| first = S. W.
| title = Triode
| encyclopedia = Newnes Dictionary of Electronics, 4th Ed.
| pages = 331
| publisher = Newnes
| year = 2002
| isbn = 9780080524054
| url = https://books.google.com/books?id=lROa-MpIrucC&q=triode&pg=PA331
| access-date = January 7, 2013}}</ref><ref name="Hijiya">{{cite book
| last = Hijiya
| first = James A.
| title = Lee de Forest
| publisher = Lehigh University Press
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| pages = 77
| url = https://books.google.com/books?id=JYylHhmoNZ4C&pg=PA77
| isbn = 0934223238}}</ref><ref name="Lee">{{cite book
| last = Lee
| first = Thomas H.
| title = Planar Microwave Engineering: A Practical Guide to Theory, Measurement, and Circuits
| publisher = Cambridge University Press
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| pages = 13–14
| url = https://books.google.com/books?id=uoj3IWFxbVYC&pg=PA13
| isbn = 0521835267}}</ref><ref name="Hempstead">{{cite book
| last1 = Hempstead
| first1 = Colin
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| pages = 643
| url = https://books.google.com/books?id=0wkIlnNjDWcC&pg=PA648
| isbn = 1579584640}}</ref> consisting of an evacuated [[glass tube]] containing three [[electrode]]s: a heated [[Electrical filament|filament]] (the cathode, made out of [[tantalum]]), a [[control grid|grid]], and a [[Plate electrode|plate]] (the anode).<ref name="Godfrey" /> It is important in the [[history of technology]] because it was the first widely used electronic device which could [[amplifier|amplify]].<ref name="Godfrey" /> A low power signal at the grid could control much more power in the plate circuit.
Audions had more [[Gas-filled tube|residual gas]] than later vacuum tubes; the residual gas limited the [[dynamic range]] and gave the Audion non-linear characteristics and erratic performance.<ref name="Okamura" /><ref name="Lee" /> Originally developed as a radio receiver [[detector (radio)|detector]]<ref name="De Forest" /> by adding a grid electrode to the [[Fleming valve]], it found little use until its amplifying ability was recognized around 1912 by several researchers,<ref name="Lee" /><ref name="Nebeker">{{cite book
| last = Nebeker
| first = Frederik
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|author-link=Edwin Howard Armstrong
|pages=215–247
|title=Some Recent Developments in the Audion Receiver
|journal=Proceedings of the IRE
|volume=3
|number=9
|date=September 1915
|url=https://books.google.com/books?id=AF0AAAAAMAAJ&pg=PA215
|doi=10.1109/jrproc.1915.216677|s2cid=2116636
}}. Republished as {{cite journal
|last=Armstrong
|first=E. H.
|author-link=Edwin Howard Armstrong
|title=Some Recent Developments in the Audion Receiver
|journal=Proceedings of the IEEE
|volume=85
|number=4
|date=April 1997
|url=http://www.ieee.org/documents/00573757.pdf
|pages=685–697
|doi=10.1109/jproc.1997.573757}}</ref> The many practical applications for amplification motivated its rapid development, and the original Audion was superseded within a few years by improved versions with a higher vacuum.<ref name="Lee" /><ref name="Nebeker" />
== History ==
[[Image:Audion receiver.jpg|thumb|
It had been known since the middle of the 19th century that gas flames were [[Electrical conduction|electrically conductive]], and early wireless experimenters had noticed that this conductivity was affected by the presence of [[Radio frequency|radio waves]]. De Forest found that gas in a partial [[vacuum]] heated by a conventional lamp filament behaved much the same way, and that if a wire were wrapped around the glass housing, the device could serve as a detector of radio signals. In his original design, a small metal plate was sealed into the lamp housing, and this was connected to the positive terminal of a
This was a significant development as existing commercial wireless systems were heavily protected by [[patent]]s; a new type of detector would allow
The Audion provided power gain; with other detectors, all of the power to operate the headphones had to come from the antenna circuit itself. Consequently, weak transmitters could be heard at greater distances.
=== Patents and disputes ===
De Forest and everybody else at the time greatly underestimated the potential of his
{{multiple image
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| image2 = Audion tube.jpg
| width2 = 162
| footer = ''(left)'' The first prototype Audion with the grid (zigzag wires) between the filament and plate.<ref name="RadioNews">{{cite journal | last =
}}
De Forest was granted a patent for his early two-electrode [[diode]] version of the Audion on November 13, 1906 ({{US patent|841386}}), and the "triode" (three-electrode) version was patented in 1908 ({{US patent|879532}}). De Forest continued to claim that he developed the Audion independently from [[John Ambrose Fleming]]'s earlier research on the [[thermionic valve]] (for which Fleming received Great Britain patent 24850 and the American [[Fleming valve]] patent {{US patent|803684}}), and
He always referred to the vacuum triodes developed by other researchers as "Oscillaudions", although there is no evidence that he had any significant input to their development. It is true that after the invention of the true vacuum triode in 1913 (see below),
In 1914, [[Columbia University]] student [[Edwin Howard Armstrong]] worked with professor [[John Harold Morecroft]] to document the electrical principles of the Audion. Armstrong published his explanation of the Audion in ''[[Electrical World]]'' in December 1914, complete with circuit diagrams and [[oscilloscope]] graphs.<ref name="Armstrong-audion">{{cite journal
|last=Armstrong
|first=E. H.
|author-link=Edwin Howard Armstrong
|title=Operating Features of the Audion
|journal=Electrical World
|volume=64
|number=24
|url=https://books.google.com/books?id=6WgfAQAAMAAJ&pg=PA1149
|pages=1149–1152
|date=December 12, 1914 }}</ref> In March and April 1915, Armstrong spoke to the [[Institute of Radio Engineers]] in New York and Boston, respectively, presenting his paper "Some Recent Developments in the Audion Receiver", which was published in September.<ref name="Armstrong1915" /> A combination of the two papers was reprinted in other journals such as the ''Annals of the New York Academy of Sciences''.<ref name="Armstrong-audion" /> When Armstrong and
The problem was that (possibly to distance his invention from the Fleming valve)
As well as
===Kenotron and Pliotron===
[[Image:Early triode vacuum tubes.jpg|thumb|upright=1.
< <li>''Bottom row (D):'' De Forest Audions
<li>''Third row (C):'' Pliotrons, developed at [[General Electric]] by Langmuir<
<li>''Second row (B):'' triodes developed at [[Western Electric]] which bought the rights from
<li>''Top row (A):'' French triodes. The French government gained the right to manufacture Audions in 1912 when
</ul>]]
Langmuir had long suspected that certain assumed limitations on the performance of various low-pressure and vacuum electrical devices, might not be fundamental physical limitations at all, but simply due to contamination and impurities in the manufacturing process. His first success was in demonstrating that, contrary to what Edison and others had long asserted, incandescent lamps could function more efficiently and with longer life if the glass envelope was filled with low-pressure inert gas rather than a complete vacuum. However, this only worked if the gas used was meticulously 'scrubbed" of all traces of oxygen and water vapor.▼
[[Image:General electric pliotron pp schenectady 3.jpg|thumb|right|General Electric Company Pliotron]]▼
▲His first success was in demonstrating that, contrary to what Edison and others had long asserted, incandescent lamps could function more efficiently and with longer life if the glass envelope was filled with low-pressure inert gas rather than a complete vacuum. However, this only worked if the gas used was meticulously 'scrubbed" of all traces of oxygen and water vapor.
He then applied the same approach to producing a rectifier for the newly developed "Coolidge" X-ray tubes. Again contrary to what had been widely believed to be possible, by virtue of meticulous cleanliness and attention to detail, he was able to produce versions of the Fleming Diode that could rectify hundreds of thousands of volts. His rectifiers were called "Kenotrons" from the Greek ''keno'' (empty, contains nothing, as in a vacuum) and ''tron'' (device, instrument).
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However he took a somewhat unorthodox approach. Instead of trying to stabilize the partial vacuum, he wondered if it was possible to make the Audion function with the total vacuum of a Kenotron, since that was somewhat easier to stabilize.
He soon realized that his "vacuum" Audion had markedly different characteristics from the
Essentially, he referred to all his vacuum tube designs as Kenotrons, the Pliotron basically being a specialized type of Kenotron. However, because Pliotron and Kenotron were registered trademarks, technical writers tended to use the more generic term "vacuum tube". By the mid-1920s, the term "Kenotron" had come to exclusively refer to vacuum tube rectifiers, while the term "Pliotron" had fallen into disuse. Ironically, in popular usage, the sound-alike brands "Radiotron" and "Ken-Rad" outlasted the original names.
== Applications and use ==
[[Image:First vacuum tube AM radio transmitter.jpg|thumb|The first Audion AM radio transmitter, built by Lee De Forest and announced April, 1914]]▼
[[Image:De Forest Audion AM radio transmitters.jpg|thumb|upright=1.5|Some of the earliest Audion AM radio transmitters, built by De Forest around 1916. The invention of the Audion oscillator in 1912 made inexpensive sound radio transmission possible, and was responsible for the advent of [[radio broadcasting]] around 1920.]] ▼
[[Image:Audion vacuum tube advertisement.png|thumb|Audion advertisement, ''Electrical Experimenter'' magazine, 1916]]▼
De Forest continued to manufacture and supply Audions to the US Navy up until the early 1920s, for maintenance of existing equipment, but elsewhere they were regarded as well and truly obsolete by then. It was the vacuum [[triode]] that made practical radio broadcasts a reality.
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In modern [[electronics]], the [[vacuum tube]] has been largely superseded by [[solid state (electronics)|solid state]] devices such as the [[transistor]], invented in 1947 and implemented in [[integrated circuit]]s in 1959, although vacuum tubes remain to this day in such applications as high-powered transmitters, guitar amplifiers and some high fidelity audio equipment.
<br><br>
'''Application images'''
<gallery>
▲[[Image:General electric pliotron pp schenectady 3.jpg|thumb|
▲
▲
▲
</gallery>
==References==
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==Further reading==
[[File:1973 airmail stamp C86.jpg|thumb|1973 postage stamp honoring
* {{cite court
|litigants= Radio Corp. v. Radio Engineering Laboratories
|vol= 293
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|url= http://wyomcases.courts.state.wy.us/applications/oscn/DeliverDocument.asp?CiteID=422515
}}
* {{citation |first=Sungook |last=Hong |title=Wireless: From Marconi's Black-box to the Audion |year=2001 |publisher=MIT Press |isbn=9780262082983 |url=https://books.google.com/books?id=UjXGQSPXvIcC&pg=PA225 |ref=none}}
* ''Where Good Ideas Come From'', Chapter V, Steven Johnson, Riverhead Books, (2011).
==External links==
{{Commons category|Audion}}
{{Wikisource|QST/March 1916/Practical Pointers on the Audion|Practical Pointers on the Audion}}
* [https://web.archive.org/web/20121010212743/http://digitalgallery.nypl.org/nypldigital/dgkeysearchdetail.cfm?trg=1&strucID=51420&imageID=99555&total=7075&num=20&word=col_id%3A187&s=1¬word=&d=&c=&f=&k=0&lWord=&lField=&sScope=images&sLevel=&sLabel=%26quot%3BThe%20Pageant%20of%20America%26quot%3B%20Photograph%20Archive&imgs=20&pos=34&e=w 1906 photograph of the original Audion tube, from New York Public Library Digital Gallery]
* {{Cite web |last=Lewis |first=Tom |date=1991 |title=Telephone History - Empire of The Air: The Men Who Made Radio |url=http://www.privateline.com/TelephoneHistory3/empireoftheair.html |url-status=dead |archive-url=https://web.archive.org/web/20140511182508/http://www.privateline.com/TelephoneHistory3/empireoftheair.html |archive-date=May 11, 2014 |website=Privateline.com}}
* http://www.britannica.com/EBchecked/topic/1262240/radio-technology/25131/The-Fleming-diode-and-De-Forest-Audion
* {{citation |url=http://www.ieee.org/publications_standards/publications/proceedings/langmuir.pdf |title=The Pure Electron Discharge and Its Applications in Radio Telegraphy and Telephony |journal=Proceedings of the IEEE |volume=85 |issue=9 |pages=
* [https://babel.hathitrust.org/cgi/pt?id=uiug.30112089533605&view=1up&seq=356 The Audion: A new Receiver for Wireless Telegraphy], Lee de Forest, Scientific American Supplement No. 1665, November 30, 1907, pages 348-350, Scientific American Supplement No. 1666, December 7, 1907, page 354–356.
* [http://120years.net/wordpress/the-audion-pianolee-de-forestusa1915/ Lee
* https://books.google.com/books?id=YEASAAAAIAAJ&pg=PA166
* {{cite journal |last=Cole |first=A. B. |title=Practical Pointers on the Audion |journal=QST |pages=
*: Also page 43 stating,
*:: Regular Audion Detector Bulbs are not adapted for the reception of continuous waves, because the vacuum is not correct for the purpose and because the filaments must be operated at such a high intensity that they give very short service, making them unnecessarily expensive.
*: Also page 44 stating,
*:: BLUE DISCHARGE OF GLOW
*:: This appears in some Audion Bulbs and not in others. If allowed to persist, the vacuum automatically increases. For this reason the glow should not be allowed to appear and certainly not to continue, as the vacuum may rise to a very high value, requiring very high voltage in the “B” battery.
{{Electronic components}}
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