In electronics, a vacuum tube (U.S. and Canadian English) or (thermionic) valve (outside North America) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. For most purposes, the vacuum tube has been replaced by the much smaller and less expensive transistor, either as a discrete device or in an integrated circuit. However, tubes are still used in several specialised applications such as audio systems and high power RF transmitters, as the display device in cathode ray tube television sets, and to generate microwaves in microwave ovens. The field of electronics comprises the study and use of systems that operate by controlling the flow of electrons (or other charge carriers) in devices such as thermionic valves and semiconductors. ... For the British rock band of the same name, see Amplifier (band) An amplifier can be considered to be any device that uses a small amount of energy to control a source of a larger amount of energy, although the term today usually refers to an electronic amplifier. ... In information theory, a signal is the sequence of states of a communications channel that encodes a message. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... Look up Vacuum in Wiktionary, the free dictionary. ... Assorted transistors The transistor is a solid state semiconductor device that can be used for amplification, switching, voltage stabilization, signal modulation and many other functions. ... Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium and gallium arsenide. ... Integrated circuit showing memory blocks, logic and input/output pads around the periphery A monolithic integrated circuit (also known as IC, microchip, silicon chip, computer chip or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) which has been manufactured in the surface... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT Electron guns Electron beams Focusing coils Deflection coils Anode connection Mask for separating beams for red, green, and blue part of displayed image Phosphor layer with red, green, and blue zones Close-up of the phosphor... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ...

The vacuum tube is a voltage-controlled device, which means that the relationship between the input and output circuits is determined by a transconductance function. The solid-state device most closely analogous to the vacuum tube is the JFET, although the vacuum tube typically operates at far higher voltage (and power) levels than the JFET. Transconductance, also known as mutual conductance, is a property of certain electronic components. ... Electric current flow from source to drain in a JFET is restricted when a voltage is applied to the gate. ...

Diode


Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ...

Triode

Explanation

Vacuum tubes, or thermionic valves, are arrangements of electrodes in a vacuum within an insulating, temperature-resistant envelope. Although the envelope was classically glass, power tubes often use ceramic and metal. The electrodes are attached to leads which pass through the envelope via an air tight seal. On most tubes, the leads are designed to plug into a tube socket for easy replacement. An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ... Look up Vacuum in Wiktionary, the free dictionary. ... Left to right: octal (top and bottom view), loctal, and miniature (top and side view) sockets. ...

The simplest vacuum tubes resemble incandescent light bulbs in that they have a filament sealed in a glass envelope which has been evacuated of all air. When hot, the filament releases electrons into the vacuum: a process called thermionic emission. The resulting negatively-charged cloud of electrons is called a space charge. These electrons will be drawn to a metal "plate" inside the envelope if the plate (also called the anode) is positively charged relative to the filament (or cathode). The result is a current of electrons flowing from filament to plate. This cannot work in the reverse direction because the plate is not heated and cannot emit electrons. This very simple example described can thus be seen to operate as a diode: a device that conducts current only in one direction. Molten glassy material glows orange with incandescence in a vitrification experiment. ... Image:Light-bulb-and-filament. ... The Electric Filament is a thread of metal which is used to convert heat into electricity for the incandescent light bulb made in 1878 by Joseph Wilson Swan ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... Thermionic emission is the flow of electrons from a metal or metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the surface. ... Space charge is the electrical current that results when a metal object is heated to incandescence in a vacuum. ... Diagram of a zinc anode in a Daniells cell. ... Note: Principals are mostly the same for hot cathode ion sources in particle accelerators to create electrons The Hot filament ionization gauge sometimes called a hot filament and hot cathode , is the most widely used vacuum (negative pressure) measuring device for the region from 10-1 to 10-9 pascals. ... Types of diodes In electronics, a diode is a component that restricts the direction of movement of charge carriers. ...

History of development

Inside of a vacuum tube with plate cut open.

The 19th century saw increasing research with evacuated tubes, such as the Geissler and Crookes tubes. Scientists who experimented with such tubes included Eugen Goldstein, Nikola Tesla, Johann Wilhelm Hittorf, Thomas Edison, and many others. These tubes were mostly for specialized scientific applications, or were novelties, with the exception of the light bulb. The groundwork laid by these scientists and inventors, however, was critical to the development of vacuum tube technology. Image File history File links Download high resolution version (955x1245, 561 KB) Summary Octal-base power w:vacuum tube cut open. ... Image File history File links Download high resolution version (955x1245, 561 KB) Summary Octal-base power w:vacuum tube cut open. ... The Geissler tube is a glass tube for demonstrating the principles of electrical discharge. ... The Crookes tube is an evacuated glass cone with 3 node elements (one anode and two cathodes). ... Among the important early researchers in X-rays were Sir William Crookes, Johann Wilhelm Hittorf, Eugene Goldstein, Heinrich Hertz, Philipp Lenard, Hermann von Helmholtz, Thomas Edison, Nikola Tesla, Charles Barkla, and Wilhelm Conrad Roentgen. ... Nikola Tesla (1856-1943) was a world-renowned Serbian inventor, physicist, mechanical engineer and electrical engineer. ... Johann Wilhelm Hittorf (March 27, 1824 – November 28, 1914) was a German physicist, born in Bonn, who observed tubes with energy rays extending from a negative electrode. ... Thomas Alva Edison (February 11, 1847 – October 18, 1931) was an American inventor and businessman who developed many devices which greatly influenced life in the 20th century. ... The light bulb is one of the most significant inventions in the history of the human race, illuminating the darkness of the evening and bringing light indoors at all times in order focus on the task at hand. ...

Though the thermionic emission effect was observed as early as 1873, it is Thomas Edison's 1883 investigation of the "Edison Effect" that is the best known. He promptly patented it (U.S. Patent 307031), but as the particle nature of the electron was not known until 1897, he did not understand the process. Thermionic emission (archaically known as the Edison effect) is the flow of electrons from a metal or metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the surface. ... Thermionic emission is the flow of electrons from a metal or metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the surface. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ...

Diodes and triodes

John Ambrose Fleming had worked for Edison; in 1904, as scientific adviser to the Marconi company, he developed the "oscillation valve" or kenotron. Later known as the diode, it allowed electric current to flow in only one direction, enabling the rectification of alternating current. Its operation is described in greater detail in the previous section. Sir John Ambrose Fleming (), (November 29, 1849 - April 18, 1945) was an English electrical engineer and physicist. ... The Marconi Company Ltd. ... Types of diodes In electronics, a diode is a component that restricts the direction of movement of charge carriers. ... Electric current is the flow of electric charge. ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ...

In 1906 Lee De Forest placed a bent wire serving as a screen between the filament and plate electrode, later known as the "grid" electrode. As the voltage applied to the grid was varied from negative to positive, the amount of electrons flowing from the filament to the plate would vary accordingly. Thus the grid was said to electrostatically "control" the plate current. The resulting three-electrode device was therefore an excellent and very sensitive amplifier of voltages. DeForest called his invention the "Audion". In 1907, DeForest filed U.S. Patent 879532 for a three-electrode version of the Audion for use in radio communications. The device is now known as the triode. De Forest's device was not strictly a vacuum tube, but clearly depended for its action on ionisation of the relatively high levels of gas remaining after evacuation. The De Forest company in its Audion leaflets warned against operation which might cause the vacuum to become too hard. The first true vacuum triodes were the Pliotrons developed by Irving Langmuir at the General Electric research laboratory (Schenectady, New York) in 1915. These were closely followed by the French 'R' Type which was in widespread use by the allied military by 1916. These two types were the first true vacuum tubes. Lee De Forest patented a three-electrode version of the Audion. ... Diagram of Vacuum-Tube Diode A plate is a type of electrode that formed part of a vacuum tube. ... The control grid is an electrode used in thermionic valves (vacuum tubes) used to modulate the flow of electrons in the cathode to anode or plate circuit. ... For the British rock band of the same name, see Amplifier (band) An amplifier can be considered to be any device that uses a small amount of energy to control a source of a larger amount of energy, although the term today usually refers to an electronic amplifier. ... The Audion is a vacuum tube device invented by Lee De Forest in 1906. ... Simplified diagram of a triode. ... Irving Langmuir -- chemist and physicist Irving Langmuir (January 31, 1881 in Brooklyn, New York - August 16, 1957 in Woods Hole, Massachusetts) was an American chemist and physicist. ... GE redirects here. ... Union Colleges Nott Memorial, one of the most recognized buildings in Schenectady Schenectady (IPA ) is a city in Schenectady County, New York, United States, of which it is the county seat. ...

The non-linear operating characteristic of the triode caused early tube audio amplifiers to exhibit distortion at low volumes. This is not to be confused with the distortion that tube amplifiers exhibit at high volume levels (known as the tube sound). To remedy the low volume distortion problem, engineers plotted curves of the applied grid voltage and resulting plate currents, and discovered that there was a range of relatively linear operation. In order to use this range, a negative voltage had to be applied to the grid to place the tube in the "middle" of the linear area with no signal applied. This was called the idle condition, and the plate current at this point the "idle current". Today this current would be called the quiescent or standing current. The controlling voltage was superimposed onto this fixed voltage, resulting in linear swings of plate current for both positive and negative swings of the input voltage. This concept was called grid bias. Valve amplifier (British English) means the same as tube amplifier (American English). ... In cell biology, quiescence is the state of cell when it is not dividing. ... Electron tubes (or valves in British English) are electronic devices with two or more electrodes; grid bias is a term used on devices with three electrodes or more, such as triodes. ...

Batteries were designed to provide the various voltages required. "A" batteries provided the filament voltage. These were often rechargable - usually of the lead-acid type ranging from 2 to 12 volts (1-6 cells) with single, double and triple cells being most common. In portable radios, flashlight bateries were sometimes used. This article or section needs additional references or sources. ... In electronics, an A battery is any battery used to provide power to the filament of a vacuum tube. ... A sealed lead acid battery. ...

The "B" batteries provided the plate voltage. These were generally of Dry cell construction, containing many small 1.5 Volt cells in series and typically came in ratings of 22.5, 45, 60, 90 or 135 volts. To this day, plate voltage is referred to as B⁺. In electronics, a B battery is any battery used to provide the plate voltage of a vacuum tube. ... // Dry cell schematic diagram A dry cell, also known as a Leclanché cell or a zinc-carbon battery, is a form of primary electrochemical cell that supplies electrical energy at small currents. ...

Some sets used "C" batteries were used to provide grid bias, although many circuits used grid leak resistors, voltage dividers or Cathode bias to provide proper tube bias. In electronics, a C battery is any battery used to provide bias to the control grid of a vacuum tube. ... Grid leak is an inherent operating characteristic of triodes and other vacuum tubes. ... Resistor symbols (US and Japan) Resistor symbols (Europe, IEC) A pack of resistors A resistor is a two-terminal electrical or electronic component that resists an electric current by producing a voltage drop between its terminals in accordance with Ohms law. ... In electronics, a voltage divider or resistor divider or potential divider is a design technique used to create a voltage (Vout) which is proportional to another voltage (Vin). ...

Direct and indirect heating

Many further innovations followed. It became common to use the filament to heat a separate electrode called the cathode, and to use the cathode as the source of electron flow in the tube rather than the filament itself. This minimized the introduction of hum when the filament was energized with alternating current. In such tubes, the filament is called a heater to distinguish it as an inactive element. City lights viewed in a motion blurred exposure. ... Software being used to design HVAC systems HVAC (pronounced either H-V-A-C or, occasionally, H-VAK) is an initialism/acronym that stands for heating, ventilation and air-conditioning. This is sometimes referred to as climate control. ...

Tetrodes and pentodes

A two-tube homemade radio from 1958. The tubes are the two columns with the dark tops. The flying leads connect to the low-voltage filament and high-voltage anode supplies.

When triodes were first used in radio transmitters and receivers, it was found that they were often unstable and had a tendency to oscillate due to parasitic anode to grid capacitance. Many complex circuits were developed to reduce this problem (e.g. the Neutrodyne amplifier), but proved unsatisfactory over wide ranges of frequencies. It was discovered that the addition of a second grid, located between the control grid and the plate and called a screen grid could solve these problems. A positive voltage slightly lower than the plate voltage was applied to it, and the screen grid was bypassed (for high frequencies) to ground with a capacitor. This arrangement decoupled the anode and the first grid, completely eliminating the oscillation problem. This two-grid tube is called a tetrode, meaning four active electrodes. Download high resolution version (600x700, 110 KB)A two-valve home-made radio from 1958. ... Download high resolution version (600x700, 110 KB)A two-valve home-made radio from 1958. ... The Neutrodyne was a particular type of Tuned Radio Frequency (TRF) radio receiver, in which the inter-electrode capacitance of the triode RF tubes are neutralised with interstage variable trim capacitors connected between the grid and plate of each RF amplifier tube. ... A grid introduced into a thermionic valve or tube to greatly reduce the capacitance between two other parts of the electrode structure. ... A tetrode is a two-grid vacuum tube. ...

Radio transmitter high power vacuum tube. The knitted copper leads provide heater current for the cathode. The tube also has a heat sink. Dubendorf museum of the military aviation.

However, the tetrode had a problem too: the positive voltage on the second grid accelerated the electrons, causing them to strike the anode hard enough to knock out secondary electrons. These could then be captured by the second grid, reducing the plate current and the amplification of the circuit. This effect was sometimes called "tetrode kink". Again the solution was to add another grid, called a suppressor grid. This third grid was biased at either ground or cathode voltage and its negative voltage (relative to the anode) electrostatically suppressed the secondary electrons by repelling them back toward the anode. This three-grid tube is called a pentode, meaning five electrodes. Image File history File linksMetadata Download high resolution version (3264x1392, 543 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Vacuum tube Metadata This file contains additional information, probably added from the digital camera or scanner used to... Image File history File linksMetadata Download high resolution version (3264x1392, 543 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Vacuum tube Metadata This file contains additional information, probably added from the digital camera or scanner used to... Dübendorf is a suburb of Zürich in Switzerland with a population of about 22,700 (2004). ... Secondary emission is a phenomenon that occurs in electron tubes where electrons impact an electrode with sufficient energy to knock additional electrons from the surface of that electrode. ... A grid used in a thermionic valve (also called vacuum tube) to suppress secondary emission. ... In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify a signal. ...

Other variations

Frequency Conversion can be accomplished by many different methods in superheterodyne receivers. Tubes with 5 grids, called pentagrid converters, were generally used although alternative such as using a combination of a triode with a hexode were also used, even octodes have been used for frequency conversion The additional grids are either control grids, with different signals applied to each one, or screen grids. In many designs a special grid acted as a second 'leaky' plate to provide a built-in oscillator, which then coupled this signal with the incoming radio signal. These signals create a single, combined effect on the plate current (and thus the signal output) of the tube circuit. The heptode, or pentagrid converter, was the most common of these. 6BE6 is an example of a heptode (note that the first number in the tube ID indicates the filament voltage). The Super Heterodyne receiver (or to give it its full name, The Supersonic Heterodyne Receiver) was invented by Edwin Armstrong in 1918. ... NOTE: This article is currently being extensively rewritten and expanded off line. ... Simplified diagram of a triode. ... NOTE: This article is currently being extensively rewritten and expanded off line. ... NOTE: This article is currently being extensively rewritten and expanded off line. ... The control grid is an electrode used in thermionic valves (vacuum tubes) used to modulate the flow of electrons in the cathode to anode or plate circuit. ... A grid introduced into a thermionic valve or tube to greatly reduce the capacitance between two other parts of the electrode structure. ... NOTE: This article is currently being extensively rewritten and expanded off line. ...

It was common practice almost everywhere in the world to combine more than one function, or more than one set of elements in the bulb of a single tube. The only constraint was where patents, and other licencing considerations required the use of multiple tubes. See British Valve Association Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ...

The RCA Type 55 for example was a double diode triode used as a detector, AVC rectifier and audio preamp in early AC powered radios. The same set of tubes often included the 53 Dual Triode Audio Output. A German firm actually built a multi-section tube with the coupling components inside the envelope. In that case the cost of individually sealing the parts in separate glass tubing to protect them from exposure to the vacuum ended up increasing the final cost. Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ... AVC is a TLA that could mean: Advanced Video Coding - a digital video compression format (see H.264/MPEG-4 AVC) Aluminum Vehicle Carrier - a new type of Autorack, a railroad freight car Asian Volleyball Confederation - (see Fédération Internationale de Volleyball) Atlantic Veterinary College - on Prince Edward Island...

Another early type of multi-section tube, the 6SN7, is a "dual triode" which, for most purposes, can perform the functions of two triode tubes, while taking up half as much space and costing less. 6SN7 is a dual triode vacuum tube, on an 8 pin octal base. ...

An RCA 12AX7 dual-triode tube (1947)

Currently the world's most popular vacuum tube is the 12AX7, with estimated annual worldwide sales of greater than 2 million units. The 12AX7 is a dual high-gain triode widely used in guitar amplifiers, audio preamps, and instruments. RCA 12AX7 tube, 1948 (captioned, made photo myself of sample tube in August 2004) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... RCA 12AX7 tube, 1948 (captioned, made photo myself of sample tube in August 2004) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... 12AX7 is a miniature dual triode vacuum tube of high gain. ... This page is about amplifiers for musical instruments. ...

The invention of the 9 pin minature tube base, besides allowing the 12AX7 Family also allowed many other multi section tubes, such as the 6GH8 triode pentode which along with a host of simalar tubes was quite popular in television receivers. Some color TV sets even used exotic types like the 6JH8 which had two plates and beam deflection electrodes (known as 'sheet beam' tube). Vacuum tubes used like this were designed for demodulation of synchronous signals, an example of which is color demodulation for television receivers. Demodulation is the act of removing the modulation from an analog signal. ...

The desire to include many functions in one envelope resulted in the General Electric Compactron A typical unit, the 6AG11 Compactron tube contained two triodes and two diodes, but many in the series had triple triodes. The Compactron is a 12-pin vacuum tube family introduced in 1961 by General Electric in Owensboro, Kentucky with the express purpose of keeping tubes in the market for a few more years during the solid state revolution. ...

An early example of multiple devices in one envelope was the 3NF. Produced by the German Loewe company as far back as 1926, the device consisted of 3 triode valves (tubes) in a single glass envelope together with all the fixed capacitors and resistors required to make a complete radio receiver. The resistors and capacitors had to be sealed in their own glass tubes to prevent them from contaminating the vacuum. The only other parts required were the HT and LT (A and B) batteries; the tuning coil; the tuning capacitor and the loudspeaker. The device was produced not to enter the integrated circuit era several decades early, but to evade German taxes levied on a per valveholder basis. As the Loewe set had only one valveholder, it was able to substantially undercut the competition. One major disadvantage of the 3NF was that if one filament failed, the whole device was rendered useless. Loewe countered this by offering a filament repair service. Integrated circuit showing memory blocks, logic and input/output pads around the periphery A monolithic integrated circuit (also known as IC, microchip, silicon chip, computer chip or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) which has been manufactured in the surface...

Loewe were to also offer the 2NF (two tetrodes plus passive components) and the WG38 (two pentodes, a triode and the passive components).

Vacuum tubes on a Philco model 20 tabletop radio set.

The beam power tube is usually a tetrode with the addition of beam-forming electrodes, which take the place of the suppressor grid. These angled plates focus the electron stream onto certain spots on the anode which can withstand the heat generated by the impact of massive numbers of electrons, while also providing pentode behavior. The positioning of the elements in a beam power tube uses a design called "critical-distance geometry", which minimizes the "tetrode kink", plate-grid capacitance, screen-grid current, and secondary emission effects from the anode, thus increasing power conversion efficiency. The control grid and screen grid are also wound with the same pitch, or number of wires per inch. Aligning the grid wires also helps to reduce screen current, which represents wasted energy. This design helps to overcome some of the practical barriers to designing high power, high efficiency power tubes. 6L6 was the first popular beam power tube, introduced by RCA in 1936. Corresponding tubes in Europe were the KT66, KT77 and KT88 by GEC (the KT standing for "Kinkless Tetrode"). Image File history File linksMetadata Vacuumtuberadio. ... Image File history File linksMetadata Vacuumtuberadio. ... Philco, the Philadelphia Electric Company (formerly known as the Spencer Company), was a pioneer in early radio and television and former employer of Philo Farnsworth, inventor of cathode ray tube television. ... The problem of secondary emission in the tetrode tube (valve) was solved by Philips/Mullard with the introduction of a suppressor grid to produce the pentode construction. ... Pair of 6L6GC tubes; (l) General Electric version from 1960s, (r) current manufacture from Svetlana Electron Devices, Russia 6L6 is the designator for a vacuum tube introduced by Radio Corporation of America RCA United States in July 1936. ... For other uses, see RCA (disambiguation). ... Original M-OV version of the KT66; this is from late production KT66 is the designator for a vacuum tube introduced by Marconi-Osram Valve Co. ...

An Electro-Harmonix 12Ax7EH Russian tube.

Variations of the 6L6 design are still widely used in guitar amplifiers, making it one of the longest lived electronic device families in history. Similar design strategies are used in the construction of large ceramic power tetrodes used in radio transmitters. Image File history File links Minaturevacuumtube. ... Image File history File links Minaturevacuumtube. ... The Electro Harmonix logo Electro Harmonix are a company that makes electronic sound processors based in New York. ...

Reliability

The chief reliability problem of a tube is that the filament or cathode is slowly "poisoned" by atoms from other elements in the tube, which damage its ability to emit electrons. Trapped gases or slow gas leaks can also damage the cathode or cause plate-current runaway due to ionization of free gas molecules. Vacuum hardness and proper selection of construction materials are the major influences on tube lifetime. Depending on the material, temperature and construction, the surface material of the cathode may also diffuse onto other elements. The resistive filaments that heat the cathodes may burn out as lamp filaments do, but usually not so quickly as they need not be so hot. In vacuum tubes, a hot cathode is a cathode electrode which emits electrons due to thermionic emission. ... ... Look up Vacuum in Wiktionary, the free dictionary. ...

Large transmitting tubes have tungsten filaments containing a small trace of thorium. A thin layer of thorium atoms forms on the outside of the wire when heated, serving as an efficient source of electrons. The thorium slowly evaporates from the wire surface, while new thorium atoms diffuse to the surface to replace them. Such thoriated tungsten cathodes routinely deliver lifetimes in the tens of thousands of hours. The claimed record is held by an Eimac power tetrode used in a Los Angeles radio station's transmitter, which was removed from service after 80,000 hours (~9 years) of uneventful operation. Transmitting tubes are claimed to survive lightning strikes more often than transistor transmitters do. General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Atomic mass 232. ... This article or section does not cite its references or sources. ...

Mazda of the UK produced a range of tubes for use in AC powered domestic receivers and other general purposes in around 1935 (the AC/ range). The British Broadcasting Corporation (BBC) used to maintain scrupulous records of equipment maintenence including the achieved life of all tubes. Their records show that a Mazda AC/HL (a triode) was removed from its equipment having achieved over 250,000 hours of service. When tested, the tube performed to the manufacturer's specification. The BBC did not claim any record for this as this order of longevity of life was typical for this range of tubes. Repair shops stocked up on spares to meet the anticipated demand for replacement tubes, but few were ever required. Any AC/ series tube encountered today is most likely unused (and may well be in its original carton).

Cathodes in small "receiving" tubes are coated with a mixture of barium oxide and strontium oxide, sometimes with addition of calcium oxide or aluminium oxide. An electric heater is inserted into the cathode sleeve, and insulated from it electrically. This complex construction causes barium and strontium atoms to diffuse to the surface of the cathode when heated to about 780 degrees Celsius, thus emitting electrons. ... Strontium Oxide SrO is formed when strontium reacts with oxygen. ... Calcium oxide (CaO), commonly known as lime, quicklime or burnt lime, is a widely used chemical compound. ... Aluminium oxide is a chemical compound of aluminium and oxygen with the chemical formula Al2O3. ...

The British found it necessary to construct the world's first electronic computer during the Second World War. This machine, named 'Colossus' required 1500 tubes. Reliability of the tubes was one of the foremost problems in the design as other large tube projects (and by large, we are talking about just a couple of hundred tubes) were proving very unreliable. Colossus's designer, Dr Tommy Flowers, had a theory that most of the unreliability was caused during power down and (mainly) power up (nobody else believed him - but that didn't stop him). Once Colossus was built and installed, it was switched on and left switched on running from dual redundant diesel generators (the war time mains supply being considered too unreliable). The only time it was switched off was for conversion to the Colussus Mk2 and the addition of another 500 or so tubes. Another 9 Colossi Mk2 were built, and all 10 machines ran with a surprising degree of reliability. The only problem was that the 10 Colossi consumed 15 kilowatts of power each, 24 hours a day, 365 days a year - nearly all of it for the tube heaters. Mushroom cloud from the nuclear explosion over Nagasaki rising 18 km into the air. ... Colossus may refer to: The Colossus of Rhodes, a giant statue of Helios, one of the Seven Wonders of the World. ...

To meet the unique reliability requirements of the early digital computer Whirlwind, it was found necessary to build special "computer vacuum tubes" with extended cathode life. The problem of short lifetime was traced to evaporation of silicon, used in the tungsten alloy to make the wire easier to draw. Elimination of the silicon from the heater wire alloy (and paying extra for more frequent replacement of the wire drawing dies) allowed production of tubes that were reliable enough for the Whirlwind project. The tubes developed for Whirlwind later found their way into the giant SAGE air-defense computer system. High-purity nickel tubing and cathode coatings free of materials that can poison emission (such as silicates and aluminum) also contribute to long cathode life. The first such "computer tube" was Sylvania's 7AK7 of 1948. By the late 1950s it was routine for special-quality small-signal tubes to last for hundreds of thousands of hours rather than thousands, if operated conservatively. This reliability made mid-cable amplifiers in submarine cables possible. The Whirlwind computer was developed at the Massachusetts Institute of Technology. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Atomic mass 183. ... A wire is a single, usually cylindrical, elongated strand of drawn metal. ... A die is a tool used in the manufacturing industry to create a wide variety of products and components. ... SAGE Sector Control Room. ... General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10, 4, d Appearance lustrous, metallic Atomic mass 58. ... In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... A submarine communications cable is a cable laid beneath the sea to carry telecommunications between countries. ...

Another important reliability problem is that the tube fails when air leaks into the tube. Usually oxygen in the air reacts chemically with the hot filament or cathode, quickly ruining it. Designers therefore worked hard to develop tube designs that sealed reliably. This was why most tubes were constructed of glass. Metal alloys (Cunife and Fernico) and glasses had been developed for light bulbs that expanded and contracted in similar amounts, as temperature changed. These made it easy to construct an insulating envelope of glass, and pass wires through the glass to the electrodes. General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance transparent (gas) very pale blue (liquid) Atomic mass 15. ... Cunife is an alloy of copper (Cu), nickel (Ni) and iron (Fe). ... An alloy of Iron (Fer), Nickel (Ni) and Cobalt (Co). ...

It is very important that the vacuum inside the envelope be as perfect, or "hard", as possible. Any gas atoms remaining will be ionized at operating voltages, and will conduct electricity between the elements in an uncontrolled manner. This can lead to erratic operation or even catastrophic destruction of the tube and associated circuitry. Unabsorbed free air sometimes ionizes and becomes visible as a pink-purple glow discharge between the tube elements. ... Electric glow discharge is a type of plasma formed by passing a current at 100V to several kV through a gas - usually argon or another noble gas. ...

To prevent any remaining gases from remaining in a free state in the tube, modern tubes are constructed with "getters", which are usually small, circular troughs filled with metals that oxidize quickly, with barium being the most common. While the tube envelope is being evacuated, the internal parts except the getter are heated by RF induction heating to extract any remaining gases from the metal. The tube is then sealed and the getter is heated to a high temperature, again by Radio frequency induction heating causing the material to evaporate, absorbing/reacting with any residual gases and usually leaving a silver-colored metallic deposit on the inside of the envelope of the tube. The getter continues to absorb any gas molecules that leak into the tube during its working life. If a tube develops a crack in the envelope, this deposit turns a white color when it reacts with atmospheric oxygen. Large transmitting and specialized tubes often use more exotic getters. Early gettered tubes used phosphorous based getters and these tubes are easily identifiable as the phosphorous leaves a characteristic orange deposit on the glass. The use of Phosphorous was short lived and was quickly replaced by the superior barium getters. Unlike the barium betters, the phosphorous did not absorb any further gasses once it had fired. A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... To prevent any remaining gases from remaining in a free state in a vacuum tube, modern tubes are constructed with getters, which are usually small, circular troughs filled with metals that oxidize quickly, with barium being the most common. ... General Name, Symbol, Number barium, Ba, 56 Chemical series alkaline earth metals Group, Period, Block 2, 6, s Appearance silvery white Atomic mass 137. ... Rough plot of Earths atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including radio waves. ... A semiconductor induction heater with a small inductor Induction heating is the process of heating a metal object by electromagnetic induction, where eddy currents are generated within the metal and resistance leads to Joule heating of the metal. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance transparent (gas) very pale blue (liquid) Atomic mass 15. ...

Some special-purpose tubes are intentionally constructed with various gases in the envelope. For instance, voltage regulator tubes contain various inert gases such as argon, helium or neon, and take advantage of the fact that these gases will ionize at predictable voltages. The thyratron is a special-purpose tube filled with low-pressure gas, for use as a high-speed electronic switch. A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. ... Gas filled tubes are arrangements of electrodes in a gas within an insulating, temperature-resistant envelope. ... An inert gas is any gas that is not reactive under normal circumstances. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Atomic mass 39. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... General Name, Symbol, Number neon, Ne, 10 Chemical series noble gases Group, Period, Block 18, 2, p Appearance colorless Atomic mass 20. ... An ion is an atom, group of atoms, or subatomic particle with a net electric charge. ... A thyratron is a type of gas filled tube used as a high energy electrical switch. ...

Tubes usually have glass envelopes, but metal, fused quartz (silica), and ceramic are possible choices. The first version of the 6L6 used a metal envelope sealed with glass beads, later a glass disk fused to the metal was used. Metal and ceramic are used almost exclusively for power tubes above 2 kW dissipation. The nuvistor is a tiny tube made only of metal and ceramic. In some power tubes, the metal envelope is also the anode. 4CX800A is an external anode tube of this sort. Air is blown through an array of fins attached to the anode, thus cooling it. Power tubes using this cooling scheme are available up to 150 kW dissipation. Above that level, water or water-vapor cooling are used. The highest-power tube currently available is the Eimac 8974, a water-cooled tetrode capable of dissipating 1.5 megawatts. (By comparison, the largest power transistor can only dissipate about 1 kilowatt). A pair of 8974s is capable of producing 2 megawatts of audio power. The 8974 is used only in exotic military and commercial radio-frequency installations. The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Fixed Partial Denture, or Bridge The word ceramic is derived from the Greek word κεραμικος (keramikos, having to do with pottery). The term covers inorganic non-metallic materials whose formation is due to the action of heat. ... The nuvistor is a type of vacuum tube announced by RCA in 1959. ...

Near the end of World War II, to make radios more rugged, some aircraft and army radios began to integrate the tube envelopes into the radio's cast aluminum or zinc chassis. The radio became just a printed circuit with non-tube components, soldered to the chassis that contained all the tubes. Another WWII idea was to make very small and rugged glass tubes, originally for use in radio-frequency metal detectors built into artillery shells. These proximity fuzes made artillery more effective. Tiny tubes were later known as "subminiature" types. They were widely used in 1950s military and aviation electronics. Combatants Allies: Soviet Union United Kingdom United States and others Axis Powers: Germany Italy Japan and others Commanders Winston Churchill Franklin Roosevelt Joseph Stalin Adolf Hitler Benito Mussolini Hideki Tojo Casualties Military dead: 17,000,000 Civilian dead: 33,000,000 Total dead: 50,000,000 Military dead: 8,000... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... A 155 mm artillery shell fired by a United States 11th Marine regiment M-198 howitzer Historically, artillery refers to any engine used for the discharge of projectiles during war. ... Look up Proximity fuze in Wiktionary, the free dictionary A proximity fuze (also called a VT fuze) is a fuze that is designed to detonate an explosive automatically when close enough to the target to destroy it. ...

Finally, when a vacuum tube is overloaded or operated past its design dissipation, its anode (plate) may glow red. In consumer equipment, a glowing plate is universally a sign of an overloaded tube and must be corrected immediately. However, some large transmitting tubes are designed to operate with their anodes at red or even orange heat. To meet Wikipedias quality standards, this article or section may require cleanup. ...

Applications

12AX7 tubes glow inside a modern guitar amplifier.

Tubes were ubiquitous in the early generations of electronic devices, such as radios, televisions, and early computers such as the Colossus which used 2000 tubes, the ENIAC which used nearly 18,000 tubes, and the IBM 700 series. Vacuum tubes inherently have higher resistance to the electromagnetic pulse effect of nuclear explosions. This property kept them in use for certain military applications long after transistors had replaced them elsewhere. Vacuum tubes are still used for very high-powered applications such as microwave ovens, industrial radio-frequency heating, and power amplification for broadcasting. Image File history File linksMetadata Download high resolution version (1024x676, 105 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Vacuum tube Metadata This file contains additional information, probably added from the digital camera or scanner... Image File history File linksMetadata Download high resolution version (1024x676, 105 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Vacuum tube Metadata This file contains additional information, probably added from the digital camera or scanner... A Lego RCX Computer is an example of an embedded computer used to control mechanical devices. ... A Colossus Mark II computer. ... ENIAC ENIAC, short for Electronic Numerical Integrator and Computer, was the first large-scale, electronic, digital computer capable of being reprogrammed to solve a full range of computing problems[1], although earlier computers had been built with some of these properties. ... The IBM 700/7000 series was a series of incompatible large scale (mainframe) computer systems made by IBM through the 1950s and early 1960s. ... It has been suggested that Electromagnetic bomb be merged into this article or section. ... It has been suggested that Nuclear explosive be merged into this article or section. ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ...

Tubes are also considered by many people in the audiophile, professional audio, and musician communities to have superior audio characteristics over transistor electronics, due to their warmer, more natural tone. There are many companies which still make specialized audio hardware featuring tube technology. Tubes' characteristic sound when overloaded is widely used in electric guitar amplification, and has defined the sound of some genres of music, including classic rock and rhythm and blues. In this regard, tube amplifiers are typically desired for the warmth and natural compression they can add to an input signal. Audiophile, from Latin audio hear and Greek φιλειν (philein) love, is a word used to describe a person dedicated to achieving high fidelity in the recording and playback of music. ... Assorted transistors The transistor is a solid state semiconductor device that can be used for amplification, switching, voltage stabilization, signal modulation and many other functions. ... Left: Rosa Hurricane, a heavy metal-style solid body guitar. ... An amplifier head An instrument amplifier is an electronic amplifier designed for use with an electric or electronic musical instrument, such as an electric guitar. ...

Other vacuum tube devices

A vast array of devices were built during the 1920-1960 period using vacuum-tube techniques. Most such tubes were rendered obsolete by semiconductors; some techniques for integrating multiple devices in a single module, sharing the same glass envelope have been discussed above, such as the Loewe 3NF. Vacuum-tube electronic devices still in common use include the magnetron, klystron, photomultiplier, x-ray tube and cathode ray tube. The magnetron is the type of tube used in all microwave ovens. In spite of the advancing state of the art in power semiconductor technology, the vacuum tube still has reliability and cost advantages for high-frequency RF power generation. Photomultipliers are still the most sensitive detectors of light. Many televisions, oscilloscopes and computer monitors still use cathode ray tubes, though flat panel displays are becoming more popular as prices drop. A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ... Reflex klystron Type 2K25 or 723 A/B. The threaded adjustment rod on the right side allows the position of the reflector to be adjusted (by compressing the reflex cavity), and thus the natural resonant frequency of the device. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ... An X-Ray tube is a vacuum tube designed to produce man made X-Ray photons on demand. ... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT Electron guns Electron beams Focusing coils Deflection coils Anode connection Mask for separating beams for red, green, and blue part of displayed image Phosphor layer with red, green, and blue zones Close-up of the phosphor... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ... A Tektronix model 475A portable analogue oscilloscope, a very typical instrument of the late 1970s. ... Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays using cathode ray tubes, usually less than 10 cm (4 inches) thick. ...

The fluorescent displays commonly used on VCRs and automotive dashboards are actually vacuum tubes, using phosphor-coated anodes to form the display characters, and a heated filamentary cathode as an electron source. These devices are properly called "VFDs", or Vacuum Fluorescent Displays. Because the filaments are in view, they must be operated at temperatures where the filament does not show a glow. Their big advantage is that it is relatively easy to create bespoke designs with all the legends required for a specific task. These devices are often found in automotive applications where their high brightness alows reading the display in daylight. A phosphor is a substance that can exhibit the phenomenon of fluorescence (glowing during absorption of radiation of another kind) or phosphorescence (sustained glowing without further stimulus). ... A vacuum fluorescent display (VFD) is a type of display used primarily on consumer-electronics equipment such as video cassette recorders. ...

Some tubes, like magnetrons, traveling wave tubes, carcinotrons, and klystrons, combine magnetic and electrostatic effects. These are efficient (usually narrow-band) RF producers and still find use in radar, microwave ovens and industrial heating. A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves. ... It has been suggested that this article or section be merged with Traveling wave tube amplifier. ... A backward wave oscillator (BWO), also called carcinotron or backward wave tube, is a device that is used to generate microwaves and terahertz radiation. ... Reflex klystron Type 2K25 or 723 A/B. The threaded adjustment rod on the right side allows the position of the reflector to be adjusted (by compressing the reflex cavity), and thus the natural resonant frequency of the device. ... This long range radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to detect, determine the distance of, and map, objects such... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ...

Gyrotrons or vacuum masers, used to generate high power millimetre band waves, are magnetic vacuum tubes in which a small relativistic effect, due to the high voltage, is used for bunching the electrons. Free electron lasers, used to generate high power coherent light and perhaps even X rays, are highly relativistic vacuum tubes driven by high energy particle accelerators. Gyrotrons are high powered electron tubes which emit a millimeter wave beam by bunching electrons with cyclotron motion in a strong magnetic field. ... Albert Einsteins theory of relativity is a set of two theories in physics: special relativity and general relativity. ... This article needs to be cleaned up to conform to a higher standard of quality. ... An X-ray picture (radiograph), taken by Wilhelm Röntgen, of Albert von Köllikers hand. ...

Particle accelerators can be considered vacuum tubes that work backward, the electric fields driving the electrons, or other changed particles. (Like ordinary vacuum tubes many of their names end in "tron".) In this respect, a cathode ray tube is a particle accelerator. A 1960s single stage 2MeV linear Van de Graaff accelerator, here opened for maintenance A particle accelerator is a device that uses electric and/or magnetic fields to propel electrically charged particles to high speeds. ...

A tube in which electrons move through a vacuum (or gaseous medium) within a gas-tight envelope is generically called an electron tube.

Vacuum tube can also literally mean a tube with a vacuum. It is e.g. used for demonstration of, and experiments with, free-fall. Look up Vacuum in Wiktionary, the free dictionary. ... Free Fall opens with one of the most stunning first paragraphs I have ever, or am ever likely to, read. ...

Field emitter vacuum tubes

In the early years of the 21st century there has been renewed interest in vacuum tubes, this time in the form of integrated circuits. The most common design uses a cold cathode field emitter, with electrons emitted from a number of sharp nano-scale tips formed on the surface of a metal cathode. The 21st century is the present century of the Gregorian calendar. ... Integrated circuit showing memory blocks, logic and input/output pads around the periphery A monolithic integrated circuit (also known as IC, microchip, silicon chip, computer chip or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) which has been manufactured in the surface... Note: Principles are mostly the same for cold cathode ion sources as in particle accelerators to create electrons. ... Also known as Fowler-Nordheim tunneling, field emission is a form of quantum tunneling in which electrons pass through a barrier in the presence of a high electric field. ...

Their advantages include greatly enhanced robustness combined with the ability to provide high power outputs at low power consumptions. Operating on the same principles as traditional tubes, prototype device cathodes have been constructed with emitter tips formed using nanotubes, and by etching electrodes as hinged flaps (similar to the technology used to create the microscopic mirrors used in Digital Light Processing) that are stood upright by a magnetic field. An electronic device known as a diode can be formed by joining two nanoscale carbon tubes with different electronic properties. ... For political parties using this acronym, see Democratic Labour Party. ... Current flowing through a wire produces a magnetic field (B, labeled M here) around the wire. ...

Such integrated microtubes may find application in microwave devices including mobile phones, for Bluetooth and Wi-Fi transmission, in radar and for satellite communication. Presently they are being studied for possible application to flat-panel display construction. Microwave image of 3C353 galaxy at 8. ... This article is about the Bluetooth wireless specification. ... Wi-Fi (also WiFi, Wi-fi, Wifi, or wifi) is a brand originally licensed by the Wi-Fi Alliance to describe the underlying technology of wireless local area networks (WLAN) based on the IEEE 802. ... This long range radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to detect, determine the distance of, and map, objects such... A satellite is any object that orbits another object (which is known as its primary). ...

Vacuum tube solar heaters

The term vacuum tube has recently been used to refer to the tubular elements of solar panels used for heating water. Vacuum tube solar heaters are becoming increasingly popular. Solar hot water describes heated water achieved through the usage of solar energy. ...

See also

• All American Five
• Gas filled tube
• Irving Langmuir
• Pneumatic tube, a device that is sometimes misnamed Vacuum tube
• Transistor
• Valve amplifier
• Valve sound
• Nixie tube, a display device which is sometimes mistaken for a vacuum tube but contains neon gas

The All American Five was a superheterodyne radio receiver designed in the USA in the 1930s and using five vacuum tubes. ... Gas filled tubes are arrangements of electrodes in a gas within an insulating, temperature-resistant envelope. ... Irving Langmuir -- chemist and physicist Irving Langmuir (January 31, 1881 in Brooklyn, New York - August 16, 1957 in Woods Hole, Massachusetts) was an American chemist and physicist. ... Pneumatic tubes, also known as capsule pipelines, are systems in which cylindrical containers are propelled through a network of tubes by compressed air or by vacuum. ... Assorted transistors The transistor is a solid state semiconductor device that can be used for amplification, switching, voltage stabilization, signal modulation and many other functions. ... A valve amplifier or tube amplifier (UK & Aus. ... Valve sound is the sound either from a valve amplifier or a specially designed transistor amplifier. ... The ten digits of a Z560M Nixie tube. ... A display device is a device for visual or tactile presentation of images (including text) acquired, stored, or transmitted in various forms. ... General Name, Symbol, Number neon, Ne, 10 Chemical series noble gases Group, Period, Block 18, 2, p Appearance colorless Atomic mass 20. ...

Patents

• U.S. Patent 307031 - Electrical indicator
• U.S. Patent 514170 - Incandescent electric light
• U.S. Patent 803684 - Instrument for converting alternating electric currents into continuous currents (Fleming Valve patent)
• U.S. Patent 841387 - Device for amplifying feeble electrical currents
• U.S. Patent 879532 - De Forest's Audion
• U.S. Patent 2141059 - Television system

The Audion is a vacuum tube device invented by Lee De Forest in 1906. ...

External links and references

Books and articles

• Spangenburg K.R., Vacuum Tubes, McGraw-Hill, 1948
• Millman, J. & Seely, S. Electronics, 2nd ed. McGraw-Hill, 1951.
• Shiers, George, "The First Electron Tube", Scientific American, March 1969, p. 104.
• Tyne, Gerald, Saga of The Vacuum Tube, Ziff Publishing, 1943, (reprint 1994 Prompt Publications), pp. 30-83.
• Stokes, John, 70 Years of Radio Tubes and Valves, Vestal Press, NY, 1982, pp. 3-9.
• Thrower, Keith, History of The British Radio Valve to 1940, MMA International, 1982, pp 9-13.
• Eastman, Austin V., Fundamentals of Vacuum Tubes, McGraw-Hill, 1949
• Philips Technical Library. A range of books published in the UK in the 1940s and 50s by Cleaver Hume Press on all aspects of the design and application of vacuum tubes. They were originally published in Dutch in Holland. French and German editions were probably also published.
• RCA "Radiotron Designer's Handbook" 1953(4th Edition) Contains very useful chapters on the design and application of receiving tubes.
• RCA "Receiving Tube Manual" RC15, RC26 (1947, 1968) Issued every two years, contains details of the technical specs of the tubes that RCA sold at the time.
• Wireless World. "Radio Designer's Handbook". UK reprint of the above.

External links

• "How vacuum tubes really work" - John Harper's webpage about thermionic emission and vacuum tube theory, using introductory college-level mathematics.
• "The invention of the thermionic valve". Fleming discovers the thermionic (or oscillation) valve, or 'diode'.
• "Tubes Vs. Transistors : Is There An Audible Difference?" - 1972 AES paper on audible differences in sound quality between vacuum tubes and transistors.
• The Virtual Valve Museum
• The Vintage Wireless Museum (Dulwich, London)
• The Cathode Ray Tube site