cathode cathoderay tube as found in an oscilloscope cutaway rendering of a color crt1three electron emitters for red green and blue phosphor dots2electron beams3focusing coils4deflection coils5connection for final anodes referred to as the ultor in some receiving tube manuals6mask for separating beams for red green and blue part of displayed image7phosphor layer screenwith red green and blue zones8closeup of the phosphorcoated inner side of the screen the cathoderay tube crt is a vacuum tube that contains one or more electron guns and a phosphorescent screen and is used to display images it modulates accelerates and deflects electron beams onto the screen to create the images the images may represent electrical waveforms oscilloscope pictures television computer monitor radar targets or other phenomena crts have also been used as memory devices in which case the visible light emitted from the fluorescent material if any is not intended to have significant meaning to a visual observer though the visible pattern on the tube face may cryptically represent the stored data in television sets and computer monitors the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster an image is produced by controlling the intensity of each of the three electron beams one for each additive primary color red green and blue with a video signal as a reference a 14inch cathoderay tube showing its deflection coils and electron guns typical 1950s united states monochrome television set a flat crt assembly inside a 1984 sinclair ftv1 pocket tv electron gun a crt is constructed from a glass envelope which is large deep ie long from front screen face to rear end fairly heavy and relatively fragile the interior of a crt is evacuated to approximately 001 pascals 99108atm evacuation being necessary to facilitate the free flight of electrons from the guns to the tubes face the fact that it is evacuated makes handling an intact crt potentially dangerous due to the risk of breaking the tube and causing a violent implosion that can hurl shards of glass at great velocity as a matter of safety the face is typically made of thick lead glass so as to be highly shatterresistant and to block most xray emissions particularly if the crt is used in a consumer product since the late 2000s crts have been largely superseded by newer flat panel display technologies such as lcd plasma display and especially oled displays which in the case of lcd and oled displays have lower manufacturing costs and power consumption as well as significantly less weight and bulk flat panel displays can also be made in very large sizes whereas 38 to 40in 97 to 102cm was about the largest size of a crt television flat panels are available in 60in 150cm and larger sizes history brauns original coldcathode crt 1897 cathode rays were discovered by johann wilhelm hittorf in 1869 in primitive crookes tubes he observed that some unknown rays were emitted from the cathode negative electrode which could cast shadows on the glowing wall of the tube indicating the rays were traveling in straight lines in 1890 arthur schuster demonstrated cathode rays could be deflected by electric fields and william crookes showed they could be deflected by magnetic fields in 1897 j j thomson succeeded in measuring the mass of cathode rays showing that they consisted of negatively charged particles smaller than atoms the first subatomic particles which were later named electrons the earliest version of the crt was known as the braun tube invented by the german physicist ferdinand braun in 1897 it was a coldcathode diode a modification of the crookes tube with a phosphorcoated screen the first cathoderay tube to use a hot cathode was developed by john b johnson who gave his name to the term johnson noise and harry weiner weinhart of western electric and became a commercial product in 1922 in 1925 kenjiro takayanagi demonstrated a crt television that received images with a 40line resolution it was named in 1929 by inventor vladimir k zworykin the first commercially made electronic television sets with cathoderay tubes were manufactured by telefunken in germany in 1934 flat panel displays dropped in price and started significantly displacing cathoderay tubes in the 2000s with lcd screens exceeding crts in 2008 the last known manufacturer of in this case recycled crts ceased in 2015 oscilloscope crts an oscilloscope showing a lissajous curve in oscilloscope crts electrostatic deflection is used rather than the magnetic deflection commonly used with television and other large crts the beam is deflected horizontally by applying an electric field between a pair of plates to its left and right and vertically by applying an electric field to plates above and below televisions use magnetic rather than electrostatic deflection because the deflection plates obstruct the beam when the deflection angle is as large as is required for tubes that are relatively short for their size phosphor persistence various phosphors are available depending upon the needs of the measurement or display application the brightness color and persistence of the illumination depends upon the type of phosphor used on the crt screen phosphors are available with persistences ranging from less than one microsecond to several seconds microchannel plate when displaying fast oneshot events the electron beam must deflect very quickly with few electrons impinging on the screen leading to a faint or invisible image on the display oscilloscope crts designed for very fast signals can give a brighter display by passing the electron beam through a microchannel plate just before it reaches the screen through the phenomenon of secondary emission this plate multiplies the number of electrons reaching the phosphor screen giving a significant improvement in writing rate brightness and improved sensitivity and spot size as well graticules most oscilloscopes have a graticule as part of the visual display to facilitate measurements the graticule may be permanently marked inside the face of the crt or it may be a transparent external plate made of glass or acrylic plastic an internal graticule eliminates parallax error but cannot be changed to accommodate different types of measurements image storage tubes the tektronix type 564 first mass produced analog phosphor storage oscilloscope these are found in analog phosphor storage oscilloscopes these are distinct from digital storage oscilloscopes which rely on solid state digital memory to store the image where a single brief event is monitored by an oscilloscope such an event will be displayed by a conventional tube only while it actually occurs the use of a long persistence phosphor may allow the image to be observed after the event but only for a few seconds at best this limitation can be overcome by the use of a direct view storage cathoderay tube storage tube a storage tube will continue to display the event after it has occurred until such time as it is erased a storage tube is similar to a conventional tube except that it is equipped with a metal grid coated with a dielectric layer located immediately behind the phosphor screen an externally applied voltage to the mesh initially ensures that the whole mesh is at a constant potential this mesh is constantly exposed to a low velocity electron beam from a flood gun which operates independently of the main gun this flood gun is not deflected like the main gun but constantly illuminates the whole of the storage mesh the initial charge on the storage mesh is such as to repel the electrons from the flood gun which are prevented from striking the phosphor screen when the main electron gun writes an image to the screen the energy in the main beam is sufficient to create a potential relief on the storage mesh the areas where this relief is created no longer repel the electrons from the flood gun which now pass through the mesh and illuminate the phosphor screen consequently the image that was briefly traced out by the main gun continues to be displayed after it has occurred the image can be erased by resupplying the external voltage to the mesh restoring its constant potential the time for which the image can be displayed was limited because in practice the flood gun slowly neutralises the charge on the storage mesh one way of allowing the image to be retained for longer is temporarily to turn off the flood gun it is then possible for the image to be retained for several days the majority of storage tubes allow for a lower voltage to be applied to the storage mesh which slowly restores the initial charge state by varying this voltage a variable persistence is obtained turning off the flood gun and the voltage supply to the storage mesh allows such a tube to operate as a conventional oscilloscope tube data storage tubes williams tube the williams tube or williamskilburn tube was a cathoderay tube used to electronically store binary data it was used in computers of the 1940s as a randomaccess digital storage device in contrast to other crts in this article the williams tube was not a display device and in fact could not be viewed since a metal plate covered its screen color crts magnified view of a deltagun shadow mask color crt magnified view of a trinitron color crt spectra of constituent blue green and red phosphors in a common crt color tubes use three different phosphors which emit red green and blue light respectively they are packed together in stripes as in aperture grille designs or clusters called triads as in shadow mask crts convergence and purity in color crts due to limitations in the dimensional precision with which crts can be manufactured economically it has not been practically possible to build color crts in which three electron beams could be aligned to hit phosphors of respective color in acceptable coordination solely on the basis of the geometric configuration of the electron gun axes and gun aperture positions shadow mask apertures etc the shadow mask ensures that one beam will only hit spots of certain colors of phosphors but minute variations in physical alignment of the internal parts among individual crts will cause variations in the exact alignment of the beams through the shadow mask allowing some electrons from for example the red beam to hit say blue phosphors unless some individual compensation is made for the variance among individual tubes color convergence and color purity are two aspects of this single problem firstly for correct color rendering it is necessary that regardless of where the beams are deflected on the screen all three hit the same spot and nominally pass through the same hole or slot on the shadow mask this is called convergence more specifically the convergence at the center of the screen with no deflection field applied by the yoke is called static convergence and the convergence over the rest of the screen area is called dynamic convergence the beams may converge at the center of the screen and yet stray from each other as they are deflected toward the edges such a crt would be said to have good static convergence but poor dynamic convergence secondly each beam must only strike the phosphors of the color it is intended to strike and no others this is called purity like convergence there is static purity and dynamic purity with the same meanings of static and dynamic as for convergence convergence and purity are distinct parameters a crt could have good purity but poor convergence or vice versa poor convergence causes color shadows or ghosts along displayed edges and contours as if the image on the screen were intaglio printed with poor registration poor purity causes objects on the screen to appear offcolor while their edges remain sharp purity and convergence problems can occur at the same time in the same or different areas of the screen or both over the whole screen and either uniformly or to greater or lesser degrees over different parts of the screen the solution to the static convergence and purity problems is a set of color alignment magnets installed around the neck of the crt these movable weak permanent magnets are usually mounted on the back end of the deflection yoke assembly and are set at the factory to compensate for any static purity and convergence errors that are intrinsic to the unadjusted tube typically there are two or three pairs of two magnets in the form of rings made of plastic impregnated with a magnetic material with their magnetic fields parallel to the planes of the magnets which are perpendicular to the electron gun axes each pair of magnetic rings forms a single effective magnet whose field vector can be fully and freely adjusted in both direction and magnitude by rotating a pair of magnets relative to each other their relative field alignment can be varied adjusting the effective field strength of the pair as they rotate relative to each other each magnets field can be considered to have two opposing components at right angles and these four components form two pairs one pair reinforcing each other and the other pair opposing and canceling each other rotating away from alignment the magnets mutually reinforcing field components decrease as they are traded for increasing opposed mutually cancelling components by rotating a pair of magnets together preserving the relative angle between them the direction of their collective magnetic field can be varied overall adjusting all of the convergencepurity magnets allows a finely tuned slight electron beam deflection or lateral offset to be applied which compensates for minor static convergence and purity errors intrinsic to the uncalibrated tube once set these magnets are usually glued in place but normally they can be freed and readjusted in the field eg by a tv repair shop if necessary on some crts additional fixed adjustable magnets are added for dynamic convergence or dynamic purity at specific points on the screen typically near the corners or edges further adjustment of dynamic convergence and purity typically cannot be done passively but requires active compensation circuits dynamic color convergence and purity are one of the main reasons why until late in their history crts were longnecked deep and had biaxially curved faces these geometric design characteristics are necessary for intrinsic passive dynamic color convergence and purity only starting around the 1990s did sophisticated active dynamic convergence compensation circuits become available that made shortnecked and flatfaced crts workable these active compensation circuits use the deflection yoke to finely adjust beam deflection according to the beam target location the same techniques and major circuit components also make possible the adjustment of display image rotation skew and other complex raster geometry parameters through electronics under user control degaussing a degaussing in progress if the shadow mask or aperture grille becomes magnetized its magnetic field alters the paths of the electron beams this causes errors of color purity as the electrons no longer follow only their intended paths and some will hit some phosphors of colors other than the one intended for example some electrons from the red beam may hit blue or green phosphors imposing a magenta or yellow tint to parts of the image that are supposed to be pure red this effect is localized to a specific area of the screen if the magnetization is localized therefore it is important that the shadow mask or aperture grille not be magnetized most color crt displays ie television sets and computer monitors each have a builtin degaussing demagnetizing circuit the primary component of which is a degaussing coil which is mounted around the perimeter of the crt face inside the bezel upon powerup of the crt display the degaussing circuit produces a brief alternating current through the degaussing coil which smoothly decays in strength fades out to zero over a period of a few seconds producing a decaying alternating magnetic field from the coil this degaussing field is strong enough to remove shadow mask magnetization in most cases in unusual cases of strong magnetization where the internal degaussing field is not sufficient the shadow mask may be degaussed externally with a stronger portable degausser or demagnetizer however an excessively strong magnetic field whether alternating or constant may mechanically deform bend the shadow mask causing a permanent color distortion on the display which looks very similar to a magnetization effect the degaussing circuit is often built of a thermoelectric not electronic device containing a small ceramic heating element and a positive thermal coefficient ptc resistor connected directly to the switched ac power line with the resistor in series with the degaussing coil when the power is switched on the heating element heats the ptc resistor increasing its resistance to a point where degaussing current is minimal but not actually zero in older crt displays this lowlevel current which produces no significant degaussing field is sustained along with the action of the heating element as long as the display remains switched on to repeat a degaussing cycle the crt display must be switched off and left off for at least several seconds to reset the degaussing circuit by allowing the ptc resistor to cool to the ambient temperature switching the displayoff and immediately back on will result in a weak degaussing cycle or effectively no degaussing cycle this simple design is effective and cheap to build but it wastes some power continuously later models especially energy star rated ones use a relay to switch the entire degaussing circuit on and off so that the degaussing circuit uses energy only when it is functionally active and needed the relay design also enables degaussing on user demand through the units front panel controls without switching the unit off and on again this relay can often be heard clicking off at the end of the degaussing cycle a few seconds after the monitor is turned on and on and off during a manually initiated degaussing cycle vector monitors vector monitor vector monitors were used in early computer aided design systems and are in some late1970s to mid1980s arcade games such as asteroids they draw graphics pointtopoint rather than scanning a raster either monochrome or color crts can be used in vector displays and the essential principles of crt design and operation are the same for either type of display the main difference is in the beam deflection patterns and circuits crt resolution dot pitch defines the maximum resolution of the display assuming deltagun crts in these as the scanned resolution approaches the dot pitch resolution moir appears as the detail being displayed is finer than what the shadow mask can render gamma crts have a pronounced triode characteristic which results in significant gamma a nonlinear relationship in an electron gun between applied video voltage and beam intensity other types cats eye magic eye tube in better quality oldfashioned tube radio sets a tuning guide consisting of a phosphor tube was used to aid the tuning adjustment this was also known as a magic eye or tuning eye tuning would be adjusted until the width of a radial shadow was minimized this was used instead of a more expensive electromechanical meter which later came to be used on higherend tuners when transistor sets lacked the high voltage required to drive the device the same type of device was used with tape recorders as a recording level meter and for various other applications including electrical test equipment charactrons charactron some displays for early computers those that needed to display more text than was practical using vectors or that required high speed for photographic output used charactron crts these incorporate a perforated metal character mask stencil which shapes a wide electron beam to form a character on the screen the system selects a character on the mask using one set of deflection circuits but that causes the extruded beam to be aimed offaxis so a second set of deflection plates has to reaim the beam so it is headed toward the center of the screen a third set of plates places the character wherever required the beam is unblanked turned on briefly to draw the character at that position graphics could be drawn by selecting the position on the mask corresponding to the code for a space in practice they were simply not drawn which had a small round hole in the center this effectively disabled the character mask and the system reverted to regular vector behavior charactrons had exceptionally long necks because of the need for three deflection systems nimo nimo tube nimo tube ba0000p31 nimo was the trademark of a family of small specialised crts manufactured by industrial electronics engineers these had 10 electron guns which produced electron beams in the form of digits in a manner similar to that of the charactron the tubes were either simple singledigit displays or more complex 4 or 6 digit displays produced by means of a suitable magnetic deflection system having little of the complexities of a standard crt the tube required a relatively simple driving circuit and as the image was projected on the glass face it provided a much wider viewing angle than competitive types eg nixie tubes flood beam crt electronstimulated luminescence flood beam crts are small tubes that are arranged as pixels for large screens like jumbotrons the first screen using this technology was introduced by mitsubishi electric for the 1980 major league baseball allstar game it differs from a normal crt in that the electron gun within does not produce a focused controllable beam instead electrons are sprayed in a wide cone across the entire front of the phosphor screen basically making each unit act as a single light bulb print head crt crts with an unphosphored front glass but with fine wires embedded in it were used as electrostatic print heads in the 1960s the wires would pass the electron beam current through the glass onto a sheet of paper where the desired content was therefore deposited as an electrical charge pattern the paper was then passed near a pool of liquid ink with the opposite charge the charged areas of the paper attract the ink and thus form the image zeus thin crt display in the late 1990s and early 2000s philips research laboratories experimented with a type of thin crt known as the zeus display which contained crtlike functionality in a flat panel display the devices were demonstrated but never marketed slimmer crt a comparison between 21inch superslim and ultraslim crt some crt manufacturers both lg display and samsung display innovated crt technology by creating a slimmer tube slimmer crt has a trade name superslim and ultraslim a 21inch 53cm flat crt has a 4472millimetre 1761in depth the depth of superslim was 352 millimetres 1386in and ultraslim was 2957 millimetres 1164in 21st century usage demise despite being a mainstay of display technology for decades crtbased computer monitors and televisions are now virtually a dead technology demand for crt screens dropped precipitously in the last half of the first decade of the 21st century the rapid advances and falling prices of lcd flat panel technology first for computer monitors and then for televisions spelled doom for competing display technologies such as crt rearprojection and plasma display most highend crt production had ceased by around 2010 in canada and the united states the sale and production of highend crt tvs 30inch 76cm screens in these markets had all but ended by 2007 just a couple of years later inexpensive combo crt tvs 20inch 51cm screens with an integrated vhs player disappeared from discount stores electronics retailers such as best buy steadily reduced store spaces for crts in 2005 sony announced that they would stop the production of crt computer displays samsung did not introduce any crt models for the 2008 model year at the 2008 consumer electronics show on 4 february 2008 they removed their 30 wide screen crts from their north american website and did not replace them with new models in the united kingdom dsg dixons the largest retailer of domestic electronic equipment reported that crt models made up 8090 of the volume of televisions sold at christmas 2004 and 1520 a year later and that they were expected to be less than 5 at the end of 2006 dixons ceased selling crt televisions in 2006 however the demise of crts has been happening more slowly in the developing world according to isupply production in units of crts was not surpassed by lcds production until 4q 2007 owing largely to crt production at factories in china causes this section does not cite any sources please help improve this section by adding citations to reliable sources unsourced material may be challenged and removed december 2017 learn how and when to remove this template message crts despite advances remained relatively heavy and cumbersome in comparison to other display technologies crt screens had much deeper cabinets compared to flat panels and rearprojection displays for a given screen size it was largely impractical to build or use crts larger than 40 inches 102cm the crt disadvantages became especially significant in light of rapid technological advancements in lcd and plasma flatpanels which allowed them to easily surpass these size limitations while also being thin and wallmountable two key features that were increasingly being preferred by customers health concerns ionizing radiation crts can emit a small amount of xray radiation as a result of the electron beams bombardment of the shadow maskaperture grille and phosphors the amount of radiation escaping the front of the monitor is widely considered not to be harmful the food and drug administration regulations in 21 cfr 102010 are used to strictly limit for instance television receivers to 05 milliroentgens per hour mrh 013ckgh or 36pakg at a distance of 5cm 2in from any external surface since 2007 most crts have emissions that fall well below this limit toxicity older color and monochrome crts may have been manufactured with toxic substances such as cadmium in the phosphors though the rear of the crt was still produced from leaded glass monochrome crts typically do not contain enough leaded glass to fail epa tclp tests while the tclp process grinds the glass into fine particles in order to expose them to weak acids to test for leachate intact crt glass does not leach the lead is vitrified contained inside the glass itself similar to leaded glass crystalware recycling due to the toxins contained in crt monitors the united states environmental protection agency created rules in october 2001 stating that crts must be brought to special ewaste recycling facilities in november 2002 the epa began fining companies that disposed of crts through landfills or incineration regulatory agencies local and statewide monitor the disposal of crts and other computer equipment various states participate in the recycling of crts each with their reporting requirements for collectors and recycling facilities for example in california the recycling of crts is governed by calrecycle the california department of resources recycling and recovery through their payment system recycling facilities that accept crt devices from business and residential sector must obtain contact information such as address and phone number to ensure the crts come from a california source in order to participate in the crt recycling payment system in europe disposal of crt televisions and monitors is covered by the weee directive flicker flicker screen at low refresh rates 60hz and below the periodic scanning of the display may produce a flicker that some people perceive more easily than others especially when viewed with peripheral vision flicker is commonly associated with crt as most televisions run at 50hz pal or 60hz ntsc although there are some 100hz pal televisions that are flickerfree typically only lowend monitors run at such low frequencies with most computer monitors supporting at least 75hz and highend monitors capable of 100hz or more to eliminate any perception of flicker though the 100 hz pal was often achieved using interleaved scanning dividing the circuit and scan into two beams of 50 hz noncomputer crts or crt for sonar or radar may have long persistence phosphor and are thus flicker free if the persistence is too long on a video display moving images will be blurred highfrequency audible noise 50hz60hz crts used for television operate with horizontal scanning frequencies of 15734hz for ntsc systems or 15625hz for pal systems this problem does not occur on 100120hz tvs and on noncga color graphics adapter computer displays because they use much higher horizontal scanning frequencies 22khz to over 100khz implosion high vacuum inside glasswalled cathoderay tubes permits electron beams to fly freelywithout colliding into molecules of air or other gas if the glass is damaged atmospheric pressure can collapse the vacuum tube into dangerous fragments which accelerate inward and then spray at high speed in all directions the implosion energy is proportional to the evacuated volume of the crt electric shock to accelerate the electrons from the cathode to the screen with sufficient velocity a very high voltage eht or extra high tension is required from a few thousand volts for a small oscilloscope crt to tens of kv for a larger screen color tv this is many times greater than household power supply voltage even after the power supply is turned off some associated capacitors and the crt itself may retain a charge for some time and therefore dissipate that charge suddenly through a ground such as an inattentive human grounding a capacitor discharge lead security concerns under some circumstances the signal radiated from the electron guns scanning circuitry and associated wiring of a crt can be captured remotely and used to reconstruct what is shown on the crt using a process called van eck phreaking recycling as electronic waste crts are considered one of the hardest types to recycle leaded crt glass was sold to be remelted into other crts or even broken down and used in road construction electronics portal basics of cathode rays and discharge in lowpressure gas cathode ray vacuum tube light production by cathode rays cathodoluminescence crookes tube phosphor scintillation physics manipulating the electron beam blanking video horizontal blanking interval vertical blanking interval deflection yoke electron beam processing electrostatic deflection electrostatic lens magnetic deflection magnetic lens applying crt in different displaypurpose analog television image displaying comparison of crt lcd plasma and oled comparison of display technology computer monitor crt projector image dissector monochrome monitor monoscope oscilloscope cathoderay oscilloscope overscan raster scan scan line miscellaneous phenomena noise video historical aspects directview bistable storage tube flat panel display history of display technology image dissector lcd television ledbacklit lcd led display penetron surfaceconduction electronemitter display trinitron safety and precautions monitor filter photosensitive epilepsy tco certification selected patents us patent 1691324 zworykin television system wikimedia commons has media related to cathode ray tube the cathode ray tube site pctechguide cathode ray tubes crts at the virtual valve museum samuel m goldwasser tv and monitor crt picture tube information vtedisplay technologyvideo displayscurrent generation eidophor electroluminescent display eld electronic paper e ink gyricon light emitting diode display led cathode ray tube crt monoscope liquidcrystal display lcd tft tn led blue phase ips plasma display panel pdp alis digital light processing dlp liquid crystal on silicon lcos next generation organic lightemitting diode oled amoled organic lightemitting transistor olet surfaceconduction electronemitter display sed field emission display fed laser tv quantum dot liquid crystal mems display imod tmos quantum dot display qdled ferro liquid crystal display flcd thickfilm dielectric electroluminescent technology tdel telescopic pixel display tpd laserpowered phosphor display lpd nonvideo electromechanical flipdot splitflap vane eggcrate fiber optic nixie tube vacuum fluorescent display vfd lightemitting electrochemical cell lec lightguide display dotmatrix display sevensegment display ssd ninesegment display fourteensegment display fsd sixteensegment display sisd 3d display stereoscopic autostereoscopic multiscopic hologram holographic display computergenerated holography volumetric musion eyeliner fog display static media movie projector neon sign destination sign slide projector transparency laser beam display capabilities edid cea861 displayid related articles history of display technology largescreen television technology optimum hdtv viewing distance highdynamicrange imaging hdri color light output flexible display comparison of display technology vteelectronic componentssemiconductor devices avalanche diode transistor tetrode transistor pentode transistor memistor memristor bipolar junction transistor bjt finfet cmos mosfet jfet fieldeffect transistor fet quantum circuit constantcurrent diode cld crd darlington transistor diac diode heterostructure barrier varactor insulatedgate bipolar transistor igbt integrated circuit ic lightemitting diode led photodetector photodiode solaristor pin diode programmable unijunction transistor put schottky diode silicon controlled rectifier scr thyristor triac unijunction transistor ujt varicap zener diode voltage regulators linear regulator lowdropout regulator switching regulator buck boost buckboost splitpi uk sepic charge pump switched capacitor vacuum tubes acorn tube audion beam tetrode barretter compactron diode fleming valve nonode nuvistor pentagrid hexode heptode octode pentode photomultiplier phototube tetrode triode vacuum tubes rf backwardwave oscillator bwo cavity magnetron crossedfield amplifier cfa gyrotron inductive output tube iot klystron maser sutton tube travelingwave tube twt cathode ray tubes beam deflection tube charactron iconoscope magic eye tube monoscope selectron tube storage tube trochotron video camera tube williams tube gasfilled tubes cold cathode crossatron dekatron ignitron krytron mercuryarc valve neon lamp nixie tube thyratron trigatron voltageregulator tube adjustable potentiometer digital variable capacitor varicap passive connector audio and video electrical power rf electrolytic detector ferrite fuse resettable resistor switch thermistor transformer varistor wire wollaston wire reactive capacitor types ceramic resonator crystal oscillator inductor parametron relay reed relay mercury switch vtethermionic valvestheoretical principles thermionic emission work function hot cathode space charge control grid suppressor grid anode glowing anode getter types diode audion triode acorn tube nuvistor tetrode beam tetrode pentode pentagrid hexode heptode octode nonode cathode ray tube additron backwardwave oscillator beam deflection tube charactron compactron eidophor iconoscope inductive output tube kinescope klystron magic eye magnetron monoscope phototube photomultiplier selectron tube storage tube sutton tube talaria projector travelingwave tube trochotron video camera tube williams tube fleming valve numbering systems rma retma marconiosram mullardphilips jis russian examples list of vacuum tubes list of tube sockets authority control gnd 41518998 ndl 00560921 