133-698: Radiotechnique (RT) was a French electronics company that made radio transmitting and receiving vacuum tubes , and later more advanced components such as integrated circuits and solar panels. At first it was a subsidiary of the French Compagnie générale de la télégraphie sans fil (CSF). Later it became a subsidiary of Philips of the Netherlands. The company expanded after World War II, moving into television and electronics, including photovoltaics and printed circuits, and in 1979 had about 15,000 employees. Later it lost market share, went through various restructurings,
266-412: A thermionic tube or thermionic valve utilizes thermionic emission of electrons from a hot cathode for fundamental electronic functions such as signal amplification and current rectification . Non-thermionic types such as a vacuum phototube , however, achieve electron emission through the photoelectric effect , and are used for such purposes as the detection of light intensities. In both types,
399-404: A beam of electrons for display purposes (such as the television picture tube, in electron microscopy , and in electron beam lithography ); X-ray tubes ; phototubes and photomultipliers (which rely on electron flow through a vacuum where electron emission from the cathode depends on energy from photons rather than thermionic emission ). A vacuum tube consists of two or more electrodes in
532-550: A blower, or water-jacket. Klystrons and magnetrons often operate their anodes (called collectors in klystrons) at ground potential to facilitate cooling, particularly with water, without high-voltage insulation. These tubes instead operate with high negative voltages on the filament and cathode. Except for diodes, additional electrodes are positioned between the cathode and the plate (anode). These electrodes are referred to as grids as they are not solid electrodes but sparse elements through which electrons can pass on their way to
665-637: A blue glow. Finnish inventor Eric Tigerstedt significantly improved on the original triode design in 1914, while working on his sound-on-film process in Berlin, Germany. Tigerstedt's innovation was to make the electrodes concentric cylinders with the cathode at the centre, thus greatly increasing the collection of emitted electrons at the anode. Irving Langmuir at the General Electric research laboratory ( Schenectady, New York ) had improved Wolfgang Gaede 's high-vacuum diffusion pump and used it to settle
798-401: A certain sound or tone). Not all electronic circuit valves or electron tubes are vacuum tubes. Gas-filled tubes are similar devices, but containing a gas, typically at low pressure, which exploit phenomena related to electric discharge in gases , usually without a heater. One classification of thermionic vacuum tubes is by the number of active electrodes . A device with two active elements
931-498: A combination of a triode with a hexode and even an octode have been used for this purpose. The additional grids include control grids (at a low potential) and screen grids (at a high voltage). Many designs use such a screen grid as an additional anode to provide feedback for the oscillator function, whose current adds to that of the incoming radio frequency signal. The pentagrid converter thus became widely used in AM receivers, including
1064-466: A common circuit (which can be AC without inducing hum) while allowing the cathodes in different tubes to operate at different voltages. H. J. Round invented the indirectly heated tube around 1913. The filaments require constant and often considerable power, even when amplifying signals at the microwatt level. Power is also dissipated when the electrons from the cathode slam into the anode (plate) and heat it; this can occur even in an idle amplifier due to
1197-579: A far superior and versatile technology for use in radio transmitters and receivers. At the end of the 19th century, radio or wireless technology was in an early stage of development and the Marconi Company was engaged in development and construction of radio communication systems. Guglielmo Marconi appointed English physicist John Ambrose Fleming as scientific advisor in 1899. Fleming had been engaged as scientific advisor to Edison Telephone (1879), as scientific advisor at Edison Electric Light (1882), and
1330-729: A garrison town with a resident general staff. The American presence is remembered today by the Woodrow Wilson Bridge over the Loire, which was officially opened in July 1918 and bears the name of the President of the United States from 1913 to 1921. Three American air force squadrons, including the 492nd, were based at the Parçay-Meslay airfield, their personnel playing an active part in the life of
1463-523: A half hours to get to Charles de Gaulle Airport . Tours has two main stations: Gare de Tours , the central station, and Gare de Saint-Pierre-des-Corps , used by trains that do not terminate in Tours. Tours Loire Valley Airport connects the Loire Valley to European cities. Historically, Tours was served by trams and trolleybuses , the trolleybus system lasting from 1949 to 1968. Tram service returned to
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#17330923832351596-400: A low potential space charge region between the anode and screen grid to return anode secondary emission electrons to the anode when the anode potential is less than that of the screen grid. Formation of beams also reduces screen grid current. In some cylindrically symmetrical beam power tubes, the cathode is formed of narrow strips of emitting material that are aligned with the apertures of
1729-573: A majority position in the new RTC. In 1988 it was renamed RTC-Philips Composants, and in 1990 Philips Composants. In 1992 this was split into Philips Composants and Philips Circuits Imprimes. In June 1998 Philips Composants, which specialized in manufacture of ceramics products, was sold to the Carbone Lorraine group and took the name Ferroxdure. In November 1998 the Aspocomp group of Finland purchased Philips circuits imprimés, which employed 550 people at
1862-414: A pair of beam deflection electrodes which deflected the current towards either of two anodes. They were sometimes known as the 'sheet beam' tubes and used in some color TV sets for color demodulation . The similar 7360 was popular as a balanced SSB (de)modulator . A beam tetrode (or "beam power tube") forms the electron stream from the cathode into multiple partially collimated beams to produce
1995-412: A printing instrument was needed. As a result of experiments conducted on Edison effect bulbs, Fleming developed a vacuum tube that he termed the oscillation valve because it passed current in only one direction. The cathode was a carbon lamp filament, heated by passing current through it, that produced thermionic emission of electrons. Electrons that had been emitted from the cathode were attracted to
2128-487: A radio station. Although France was not immediately affected by the Great Depression , CSF felt the effect in 1929 since radio transmission was mainly the result of global commercial activity. In 1929 CSF transferred production of Radiola's consumer radio sets from SFR to Radiotechnique. There was a legal dispute in 1929 between CSF and Philips of the Netherlands over patents for the new radio sets connected directed to
2261-506: A relatively low-value resistor is connected between the cathode and ground. This makes the cathode positive with respect to the grid, which is at ground potential for DC. However C batteries continued to be included in some equipment even when the "A" and "B" batteries had been replaced by power from the AC mains. That was possible because there was essentially no current draw on these batteries; they could thus last for many years (often longer than all
2394-407: A simple oscillator only requiring connection of the plate to a resonant LC circuit to oscillate. The dynatron oscillator operated on the same principle of negative resistance as the tunnel diode oscillator many years later. The dynatron region of the screen grid tube was eliminated by adding a grid between the screen grid and the plate to create the pentode . The suppressor grid of the pentode
2527-419: A small-signal vacuum tube are 1 to 10 millisiemens. It is one of the three 'constants' of a vacuum tube, the other two being its gain μ and plate resistance R p or R a . The Van der Bijl equation defines their relationship as follows: g m = μ R p {\displaystyle g_{m}={\mu \over R_{p}}} The non-linear operating characteristic of
2660-544: A square with busy pubs and restaurants, whose open-air tables fill the centre of the square. The Boulevard Beranger crosses the Rue Nationale at the Place Jean-Jaures and is the location of weekly markets and fairs. Tours is famous for its many bridges crossing the river Loire. One of them, Wilson Bridge, collapsed in 1978 but was rebuilt. In the garden of the ancient Palais des Archevêques (now Musée des Beaux-Arts )
2793-557: A territory bitterly disputed between the counts of Blois and Anjou – the latter were victorious in the 11th century. It was the capital of France at the time of Louis XI, who had settled in the castle of Montils (today the castle of Plessis-les-Tours, at the junction of the Loire and the Indre rivers ). Tours and Touraine remained a permanent residence of the kings and court until the 16th century. The Renaissance gave Tours and Touraine many private mansions and castles, joined to some extent under
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#17330923832352926-470: A transmitting tube as background. When the thoriated filament was introduced in 1923 the R was replaced by RT. In 1924 the company launched Super-Micro and Radio-Watt tubes. For a short period Radiotechnique used the "Doria" brand for American-style tubes. In 1927 the Dario trademark was adopted, but some tubes were marked as both RT and Dario. The Radiola brand appeared in 1922 for a receptor made by SFR. Later it
3059-464: A vacuum inside an airtight envelope. Most tubes have glass envelopes with a glass-to-metal seal based on kovar sealable borosilicate glasses , although ceramic and metal envelopes (atop insulating bases) have been used. The electrodes are attached to leads which pass through the envelope via an airtight seal. Most vacuum tubes have a limited lifetime, due to the filament or heater burning out or other failure modes, so they are made as replaceable units;
3192-731: A volleyball club named the Tours VB . Tours is a special place for Catholics who follow the devotion to the Holy Face of Jesus and the adoration of the Blessed Sacrament . In 1843, Sister Marie of St Peter of Tours reported a vision which started the devotion to the Holy Face of Jesus , in reparation for the many insults Christ suffered in His Passion. The Golden Arrow Prayer was first made public by her. The Venerable Leo Dupont also known as The Holy Man of Tours lived in Tours at about
3325-429: A wide range of frequencies. To combat the stability problems of the triode as a radio frequency amplifier due to grid-to-plate capacitance, the physicist Walter H. Schottky invented the tetrode or screen grid tube in 1919. He showed that the addition of an electrostatic shield between the control grid and the plate could solve the problem. This design was refined by Hull and Williams. The added grid became known as
3458-445: Is a current . Compare this to the behavior of the bipolar junction transistor , in which the controlling signal is a current and the output is also a current. For vacuum tubes, transconductance or mutual conductance ( g m ) is defined as the change in the plate(anode)/cathode current divided by the corresponding change in the grid to cathode voltage, with a constant plate(anode) to cathode voltage. Typical values of g m for
3591-489: Is a diode , usually used for rectification . Devices with three elements are triodes used for amplification and switching . Additional electrodes create tetrodes , pentodes , and so forth, which have multiple additional functions made possible by the additional controllable electrodes. Other classifications are: Vacuum tubes may have other components and functions than those described above, and are described elsewhere. These include as cathode-ray tubes , which create
3724-452: Is a huge cedar tree said to have been planted by Napoleon . The garden also has a stuffed elephant named Fritz. He escaped from the Barnum and Bailey circus during their stay in Tours in 1902. He went mad and had to be shot down, but the city paid to honor him, and he was taxidermied as a result. Tours is home to University of Tours (formerly known as University François Rabelais of Tours),
3857-449: Is a popular culinary city with specialties such as: rillettes , rillons, Touraine vineyards , AOC Sainte-Maure-de-Touraine cheeses and nougats . The city is also the end-point of the annual Paris–Tours cycle race . A popular folk etymology of the word "Tours" is that it comes from Turonus , the nephew of Brutus . Turonus died in a war between Corineus and the king of Aquitaine , Goffarius Pictus , provoked by Corineus hunting in
3990-515: Is explained by the fact that the court of France lived in Touraine between 1430 and 1530. French, the language of the court, had become the official language of the entire kingdom. A Council of Tours in 813 decided that priests should preach sermons in different languages because the common people could no longer understand classical Latin . This was the first official recognition of an early French language distinct from Latin, and can be considered as
4123-410: Is not important since they are simply re-captured by the plate. But in a tetrode they can be captured by the screen grid since it is also at a positive voltage, robbing them from the plate current and reducing the amplification of the tube. Since secondary electrons can outnumber the primary electrons over a certain range of plate voltages, the plate current can decrease with increasing plate voltage. This
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4256-551: Is the Loewe 3NF . This 1920s device has three triodes in a single glass envelope together with all the fixed capacitors and resistors required to make a complete radio receiver. As the Loewe set had only one tube socket, it was able to substantially undercut the competition, since, in Germany, state tax was levied by the number of sockets. However, reliability was compromised, and production costs for
4389-416: Is the dynatron region or tetrode kink and is an example of negative resistance which can itself cause instability. Another undesirable consequence of secondary emission is that screen current is increased, which may cause the screen to exceed its power rating. The otherwise undesirable negative resistance region of the plate characteristic was exploited with the dynatron oscillator circuit to produce
4522-538: Is the largest city in the region of Centre-Val de Loire , France. It is the prefecture of the department of Indre-et-Loire . The commune of Tours had 136,463 inhabitants as of 2018 while the population of the whole metropolitan area was 516,973. Tours sits on the lower reaches of the Loire , between Orléans and the Atlantic coast. Formerly named Caesarodunum by its founder, Roman Emperor Augustus , it possesses one of
4655-473: Is very mild for such a northern latitude. Summers are influenced by its inland position, resulting in frequent days of 25 °C (77 °F) or warmer, whereas winters are kept mild by Atlantic air masses. The entire valley between Orlans and Angers is famous for the luminosity of its air and for its fabulous châteaux, most of them Renaissance (over 600 between Orlans and Angers). The Cathedral of Tours, dedicated to Saint Gatien , its canonized first bishop ,
4788-556: The Edison effect , that became well known. Although Edison was aware of the unidirectional property of current flow between the filament and the anode, his interest (and patent ) concentrated on the sensitivity of the anode current to the current through the filament (and thus filament temperature). It was years later that John Ambrose Fleming applied the rectifying property of the Edison effect to detection of radio signals, as an improvement over
4921-661: The plate ( anode ) when the plate was at a positive voltage with respect to the cathode. Electrons could not pass in the reverse direction because the plate was not heated and not capable of thermionic emission of electrons. Fleming filed a patent for these tubes, assigned to the Marconi company, in the UK in November 1904 and this patent was issued in September 1905. Later known as the Fleming valve ,
5054-429: The screen grid or shield grid . The screen grid is operated at a positive voltage significantly less than the plate voltage and it is bypassed to ground with a capacitor of low impedance at the frequencies to be amplified. This arrangement substantially decouples the plate and the control grid , eliminating the need for neutralizing circuitry at medium wave broadcast frequencies. The screen grid also largely reduces
5187-469: The 6GH8 /ECF82 triode-pentode, quite popular in television receivers. The desire to include even more functions in one envelope resulted in the General Electric Compactron which has 12 pins. A typical example, the 6AG11, contains two triodes and two diodes. Some otherwise conventional tubes do not fall into standard categories; the 6AR8, 6JH8 and 6ME8 have several common grids, followed by
5320-482: The 6SN7 , is a "dual triode" which performs the functions of two triode tubes while taking up half as much space and costing less. The 12AX7 is a dual "high mu" (high voltage gain ) triode in a miniature enclosure, and became widely used in audio signal amplifiers, instruments, and guitar amplifiers . The introduction of the miniature tube base (see below) which can have 9 pins, more than previously available, allowed other multi-section tubes to be introduced, such as
5453-692: The Battle of Tours . The Muslim army was defeated, preventing an Islamic conquest of France. In 845, Tours repelled the first attack of the Viking chief Haesten . In 850, the Vikings settled at the mouths of the Seine and the Loire. Still led by Haesten, they went up the Loire again in 852 and sacked Angers , Tours and Marmoutier Abbey. During the Middle Ages, Tours consisted of two juxtaposed and competing centres. The "City" in
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5586-571: The Midland Bank of London, which was represented on the board by Guy Thurneyssen. The two Radiotechnique factories, making tubes and radio sets, covered a large area on both sides of the Rue Carnot, connected by an underground passage. 93% of the tubes were used for consumer radio sets, the others being used for the PTT, army and other purposes. At the end of 1937 sales volumes were well below expectations and
5719-533: The UNESCO , and is home to the Vieux-Tours, a patrimonial site. The garden city has a green heritage and an urban landscape strongly influenced by its natural space. The historic city that is nicknamed " Le Petit Paris " and its region by its history and culture has always been a land of birth or host to many personalities, international sporting events, and is a university city with more than 30,000 students in 2019. Tours
5852-464: The magnetic detector . Amplification by vacuum tube became practical only with Lee de Forest 's 1907 invention of the three-terminal " audion " tube, a crude form of what was to become the triode . Being essentially the first electronic amplifier , such tubes were instrumental in long-distance telephony (such as the first coast-to-coast telephone line in the US) and public address systems , and introduced
5985-468: The quiescent current necessary to ensure linearity and low distortion. In a power amplifier, this heating can be considerable and can destroy the tube if driven beyond its safe limits. Since the tube contains a vacuum, the anodes in most small and medium power tubes are cooled by radiation through the glass envelope. In some special high power applications, the anode forms part of the vacuum envelope to conduct heat to an external heat sink, usually cooled by
6118-462: The spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, and created the discipline of electronics . In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, safer, cooler, and more efficient, reliable, durable, and economical than thermionic tubes. Beginning in
6251-417: The 18th-century architecture. Pierre Patout succeeded Lefèvre as the architect in charge of rebuilding in 1945. At one time, there was talk of demolishing the southern side of the rue Nationale to make it in keeping with the new development. The recent history of Tours is marked by the personality of Jean Royer , who was mayor for 36 years and helped save the old town from demolition by establishing one of
6384-476: The 1920s the company made wireless telephony transmitters and receiving sets, receiving tubes ( lampes de réception ) and amplifiers. Yves Rocard , a graduate of the Ecole Normale, was recruited in 1928 by Roger Julia, the director of the company, and given the task of producing triodes for the new radio sets. Maurice Ponte was hired soon after. The "Radiola" trademark was used for radio receivers as well as for
6517-413: The 19th century, telegraph and telephone engineers had recognized the need to extend the distance that signals could be transmitted. In 1906, Robert von Lieben filed for a patent for a cathode-ray tube which used an external magnetic deflection coil and was intended for use as an amplifier in telephony equipment. This von Lieben magnetic deflection tube was not a successful amplifier, however, because of
6650-496: The 20th century progressed, Tours became a dynamic conurbation, economically oriented towards the service sector. The city was greatly affected by the First World War . A force of 25,000 American soldiers arrived in 1917, setting up textile factories for the manufacture of uniforms, repair shops for military equipment, munitions dumps, an army post office and an American military hospital at Augustins. Because of this, Tours became
6783-481: The Audion for demonstration to AT&T's engineering department. Dr. Harold D. Arnold of AT&T recognized that the blue glow was caused by ionized gas. Arnold recommended that AT&T purchase the patent, and AT&T followed his recommendation. Arnold developed high-vacuum tubes which were tested in the summer of 1913 on AT&T's long-distance network. The high-vacuum tubes could operate at high plate voltages without
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#17330923832356916-633: The Catholics returned to power in Angers: the attendant assumed the right to nominate the aldermen. The Massacre of Saint-Barthelemy was not repeated at Tours. The Protestants were imprisoned by the aldermen – a measure which prevented their extermination. The permanent return of the Court to Paris and then Versailles marked the beginning of a slow but permanent decline. Guillaume the Metayer (1763–1798), known as Rochambeau ,
7049-579: The French Army, and increased its workforce to 1,400. The share of tubes for the consumer market fell to 44%. Given the large British participation, when the Germans occupied Paris they considered Radiotechnique to be spoils of war ( Beutelager ) and requisitioned the Suresnes factory on 24 June 1940. Some of the equipment from the tubes factory was removed. The factory was allowed to resume production of equipment for
7182-538: The Holy Face on Rue St. Etienne in Tours receives many pilgrims every year. Tours was the site of the episcopal activity of St. Martin of Tours and has further Christian connotations in that the pivotal Battle of Tours in 732 is often considered the first decisive victory over the invading Islamic forces, turning the tide against them. The battle also helped lay the foundations of the Carolingian Empire . Tours
7315-510: The Loire to the north and the Cher to the south. The buildings of Tours are white with blue slate (called Ardoise ) roofs; this style is common in the north of France, while most buildings in the south of France have terracotta roofs. Tours is famous for its original medieval district, called le Vieux Tours . Unique to the Old City are its preserved half-timbered buildings and la Place Plumereau ,
7448-609: The Philips BPx47 range solar panel while LEP undertook research into applied photovoltaics . As of 1979 La Radiotechnique was a major manufacturer of electronics equipment, radio receivers and television sets under the "Radiola" and "Philips" brands. The Radiotechnique group had about 15,000 employees in France. Radiotechnique began commercial production of semiconductors around 1954. In 1965 all electronic component research, development and production, previously distributed between Coprim and
7581-715: The Radiotechnique "Tubes and Semiconductors" division was grouped into the new subsidiary Radiotechnique-Coprim (RTC). Radiotechnique became the parent company for RTC and LEP. In June 1967 Philips, Radiotechnique and the Compagnie Générale d'Electricité formed a joint venture named RTC: Radiotechnique-Compelec. This took over all the industrial establishments in Caen, Chartres, Dreux, Évreux, Suresnes, Tours and Joué-lès-Tours. It made ferrite cores, printed circuits, ceramic dielectric capacitors, memory matrices and wirewound resistors. In
7714-400: The allied military by 1916. Historically, vacuum levels in production vacuum tubes typically ranged from 10 μPa down to 10 nPa (8 × 10 Torr down to 8 × 10 Torr). The triode and its derivatives (tetrodes and pentodes) are transconductance devices, in which the controlling signal applied to the grid is a voltage , and the resulting amplified signal appearing at the anode
7847-408: The area around the railway station in 1944, causing several hundred deaths. A plan for the rebuilding of the central area drawn up by the local architect Camille Lefèvre had been adopted even before the end of the war. The plan was for 20 small quadrangular blocks of housing to be arranged around the main road (la rue Nationale ), which was widened. This regular layout attempted to echo but simplify
7980-409: The base. There was even an occasional design that had two top cap connections. The earliest vacuum tubes evolved from incandescent light bulbs , containing a filament sealed in an evacuated glass envelope. When hot, the filament in a vacuum tube (a cathode ) releases electrons into the vacuum, a process called thermionic emission . This can produce a controllable unidirectional current though
8113-615: The birth of French. The Ordinance of Montils-lès-Tours , promulgated by Charles VII in 1454, made it mandatory to write laws and oral customs in the native language of the area. An ordinance of Charles VIII (born in Amboise , near Tours) in 1490 and one of Louis XII (born in Blois , near Tours) in 1510 broaden the scope of the ordinance of Charles VII. Finally, the Ordinance of Villers-Cotterêts , signed into law by Francis I in 1539, called for
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#17330923832358246-567: The cathedral itself. Before the French Revolution , the inhabitants of Tours ( Les Tourangeaux ) were known for speaking the "purest" form of French in the entire country. The pronunciation of Touraine was traditionally regarded as the most standard pronunciation of the French language, until the 19th century when the standard pronunciation of French shifted to that of the Parisian bourgeoisie. That
8379-480: The cathedral. Another bone of contention was the original Vinci Congress Centre by Jean Nouvel . The project incurred debts although it at least made Tours one of France's principal conference centres. Jean Germain , a member of the Socialist Party, became mayor in 1995 and made debt reduction his priority. Ten years later, his economic management was regarded as much wiser than that of his predecessor because of
8512-536: The cathode, no direct current could pass from the cathode to the grid. Thus a change of voltage applied to the grid, requiring very little power input to the grid, could make a change in the plate current and could lead to a much larger voltage change at the plate; the result was voltage and power amplification . In 1908, de Forest was granted a patent ( U.S. patent 879,532 ) for such a three-electrode version of his original Audion for use as an electronic amplifier in radio communications. This eventually became known as
8645-483: The city centre. Some architectural masterpieces of the 16th and 17th centuries were lost, as was the monumental entry to the city. The Wilson Bridge, which carried a water main that supplied the city, was dynamited to slow the progress of the German advance. With the water main severed, nobody could extinguish the inferno. That made inhabitants have no option but to flee to safety. More heavy air raids by Allied forces devastated
8778-587: The city in 2013, when a new tram system began operation. Twenty-one Alstom Citadis trams were ordered. There is also a bus service, the main central stop being Jean Jaurès , next to the Hôtel de Ville , and rue Nationale , the high street of Tours. The tram and bus networks are operated by Fil Bleu and they share a ticketing system. A second tram line is scheduled for 2025. The city's football team, Tours FC , currently play in Championnat National 3 ,
8911-646: The city. Americans paraded at funerals and award ceremonies for the Croix de Guerre. They also took part in festivals and their YMCA organised shows for the troops. Some men married women from Tours. In 1920, the city hosted the Congress of Tours, which saw the creation of the French Communist Party . One future consequence of that congress was the presence of Ho Chi Minh , the Vietnamese nationalist, who became one of
9044-468: The control grid, reducing control grid current. This design helps to overcome some of the practical barriers to designing high-power, high-efficiency power tubes. Manufacturer's data sheets often use the terms beam pentode or beam power pentode instead of beam power tube , and use a pentode graphic symbol instead of a graphic symbol showing beam forming plates. Tours Tours ( / t ʊər / TOOR , French: [tuʁ] )
9177-559: The east, successor of the late Roman ' castrum ', was composed of the cathedral and palace of the archbishops as well as the castle of Tours. The castle of Tours acted as a seat of the authority of the Counts of Tours (later Counts of Anjou) and the King of France. In the west, the "new city" structured around the Abbey of Saint Martin was freed from the control of the city during the 10th century (an enclosure
9310-418: The electrode leads connect to pins on the tube's base which plug into a tube socket . Tubes were a frequent cause of failure in electronic equipment, and consumers were expected to be able to replace tubes themselves. In addition to the base terminals, some tubes had an electrode terminating at a top cap . The principal reason for doing this was to avoid leakage resistance through the tube base, particularly for
9443-426: The electrons are accelerated from the cathode to the anode by the electric field in the tube. The simplest vacuum tube, the diode (i.e. Fleming valve ), was invented in 1904 by John Ambrose Fleming . It contains only a heated electron-emitting cathode and an anode. Electrons can flow in only one direction through the device – from the cathode to the anode. Adding one or more control grids within
9576-425: The exception of early light bulbs , such tubes were only used in scientific research or as novelties. The groundwork laid by these scientists and inventors, however, was critical to the development of subsequent vacuum tube technology. Although thermionic emission was originally reported in 1873 by Frederick Guthrie , it was Thomas Edison's apparently independent discovery of the phenomenon in 1883, referred to as
9709-552: The fifth level of French football . They also have a second team, CCSP Tours . CCSP's home stadium is the Stade des Tourettes and they play in the Division d'Honneur Regionale de Centre , the seventh tier of the French football league system . Tours has served as the finish location for Paris–Tours , a one-day road cycling classic race held almost every October since 1896. Tours also has
9842-403: The filament as the cathode; this is called a "directly heated" tube. Most modern tubes are "indirectly heated" by a "heater" element inside a metal tube that is the cathode. The heater is electrically isolated from the surrounding cathode and simply serves to heat the cathode sufficiently for thermionic emission of electrons. The electrical isolation allows all the tubes' heaters to be supplied from
9975-454: The financial stability of the city returning. However, his achievements were criticised by the municipal opposition for a lack of ambition. There were no large building projects instituted under his two terms. That position is disputed by those in power, who affirm their policy of concentrating on the quality of life, as evidenced by urban restoration, the development of public transport and cultural activities. Tours has an oceanic climate that
10108-652: The first Conservation Areas . This example of conservation policy would later inspire the Malraux Law for the safeguarding of historic city centres. In the 1970s, Jean Royer also extended the city to the south by diverting the course of the Cher River to create the districts of Rives du Cher and des Fontaines. At the time, it was one of the largest urban developments in Europe. In 1970, the François Rabelais University
10241-484: The first members of the party. Tours was also marked by the Second World War , as the city suffered massive destruction in 1940. For four years it was a city of military camps and fortifications. From 10 to 13 June 1940, Tours was the temporary seat of the French government before its move to Bordeaux . German incendiary bombs caused a huge fire, which blazed out of control from 20 to 22 June and destroyed part of
10374-528: The foundry and Firmin-Didot, were too highly skilled for routine production-line assembly jobs. They were unionized and demanded higher wages than the company could afford. The new plants were short of several hundred workers when they opened. Radiotechnique brought in workers from Italy, Hungary and Spain to open the factory, but there was high turnover. In the following years recruiters continued to hire semiskilled workers in Italy, Spain and Morocco. By 1970 about 39% of
10507-536: The generic name of the Châteaux of the Loire. It is also at the time of Louis XI that the silk industry was introduced – despite difficulties, the industry still survives to this day. Charles IX passed through the city at the time of his royal tour of France between 1564 and 1566, accompanied by the Court and various noblemen: his brother the Duke of Anjou , Henri de Navarre , the cardinals of Bourbon and Lorraine . At this time,
10640-400: The high impedance grid input. The bases were commonly made with phenolic insulation which performs poorly as an insulator in humid conditions. Other reasons for using a top cap include improving stability by reducing grid-to-anode capacitance, improved high-frequency performance, keeping a very high plate voltage away from lower voltages, and accommodating one more electrode than allowed by
10773-411: The influence of the plate voltage on the space charge near the cathode, permitting the tetrode to produce greater voltage gain than the triode in amplifier circuits. While the amplification factors of typical triodes commonly range from below ten to around 100, tetrode amplification factors of 500 are common. Consequently, higher voltage gains from a single tube amplification stage became possible, reducing
10906-698: The influence of the saint, the abbey and the city in Gaul. In the 9th century, Tours was at the heart of the Carolingian Renaissance , in particular because of Alcuin , of York in Northumbria, a renowned book collector and an abbot of Marmoutier Abbey . In 732, Abdul Rahman Al Ghafiqi and an army of Muslim horsemen from Al-Andalus advanced 500 kilometres (300 miles) deep into France, and were stopped at Moussais-la-Bataille (between Châtellerault and Poitiers ) by Charles Martel and his infantry. This ignited
11039-509: The king's forests without permission. It is said that Turonus was buried in Tours and the city is founded around his grave. In Gallic times, Tours was an important crossing point over the Loire . It became part of the Roman Empire during the 1st century AD, and the city was named Caesarodunum ("hill of Caesar"). The name evolved in the 4th century when the original Gallic name, Turones , became Civitas Turonum and then Tours . It
11172-724: The largest amphitheaters of the Roman Empire, the Tours Amphitheatre . Known for the Battle of Tours in 732 AD, it is a National Sanctuary with connections to the Merovingians and the Carolingians , with the Capetians making the kingdom's currency the Livre tournois . Saint Martin and Gregory of Tours were from Tours. Tours was once part of Touraine , a former province of France. Tours
11305-516: The late 1960s Radiotechnique produced Sylvania 's SUHL-TTL integrated circuits, which were sold to the French computer maker Bull and to the computer division of Philips. In 1968 Radiotechnique Compelec had 22% of the French semiconductor market, ahead of Sescosem and Texas Instruments , who both had 20%. Radiotechnique was later adversely affected when Sylvania lost market share to Texas Instruments. As of 1 January 1986 RTC la Radiotechnique-Compelec, Hyperelec and Cima became RTC-Compelec. Philips had
11438-428: The mains electricity, which CSF won. However, CSF made an agreement with Philips under which CSF would drop its amateur equipment line and Philips would not compete on professional equipment. Radiotechnique was purchased by Philips in 1931. Philips bought only half the shares of Radiotechnique, but in practice fully controlled the subsidiary. CSF used the sale of its stake in Radiotechnique to strengthen its position in
11571-573: The mid-1960s, thermionic tubes were being replaced by the transistor . However, the cathode-ray tube (CRT) remained the basis for television monitors and oscilloscopes until the early 21st century. Thermionic tubes are still employed in some applications, such as the magnetron used in microwave ovens, certain high-frequency amplifiers , and high end audio amplifiers, which many audio enthusiasts prefer for their "warmer" tube sound , and amplifiers for electric musical instruments such as guitars (for desired effects, such as "overdriving" them to achieve
11704-501: The miniature tube version of the " All American Five ". Octodes, such as the 7A8, were rarely used in the United States, but much more common in Europe, particularly in battery operated radios where the lower power consumption was an advantage. To further reduce the cost and complexity of radio equipment, two separate structures (triode and pentode for instance) can be combined in the bulb of a single multisection tube . An early example
11837-431: The number of external pins (leads) often forced the functions to share some of those external connections such as their cathode connections (in addition to the heater connection). The RCA Type 55 is a double diode triode used as a detector, automatic gain control rectifier and audio preamplifier in early AC powered radios. These sets often include the 53 Dual Triode Audio Output. Another early type of multi-section tube,
11970-435: The number of tubes required. Screen grid tubes were marketed by late 1927. However, the useful region of operation of the screen grid tube as an amplifier was limited to plate voltages greater than the screen grid voltage, due to secondary emission from the plate. In any tube, electrons strike the plate with sufficient energy to cause the emission of electrons from its surface. In a triode this secondary emission of electrons
12103-523: The oscillation valve was developed for the purpose of rectifying radio frequency current as the detector component of radio receiver circuits. While offering no advantage over the electrical sensitivity of crystal detectors , the Fleming valve offered advantage, particularly in shipboard use, over the difficulty of adjustment of the crystal detector and the susceptibility of the crystal detector to being dislodged from adjustment by vibration or bumping. In
12236-438: The plant was closed to dispose of stocks. There were 1,200 employees in 1936–37, which fell to 700 in the years that followed. In 1939 CSF still held 49.9% of the capital of Radiotechnique, but Philips controlled the company. Many of the radio sets sold under CSF's former "Radiola" trademark were imported from the Netherlands. At the start of World War II (1939–45) Radiotechnique received important orders for radio equipment from
12369-647: The plate current, possibly changing the output by hundreds of volts (depending on the circuit). The solid-state device which operates most like the pentode tube is the junction field-effect transistor (JFET), although vacuum tubes typically operate at over a hundred volts, unlike most semiconductors in most applications. The 19th century saw increasing research with evacuated tubes, such as the Geissler and Crookes tubes . The many scientists and inventors who experimented with such tubes include Thomas Edison , Eugen Goldstein , Nikola Tesla , and Johann Wilhelm Hittorf . With
12502-471: The plate, it creates an electric field due to the potential difference between them. Such a tube with only two electrodes is termed a diode , and is used for rectification . Since current can only pass in one direction, such a diode (or rectifier ) will convert alternating current (AC) to pulsating DC. Diodes can therefore be used in a DC power supply , as a demodulator of amplitude modulated (AM) radio signals and for similar functions. Early tubes used
12635-405: The plate. The vacuum tube is then known as a triode , tetrode , pentode , etc., depending on the number of grids. A triode has three electrodes: the anode, cathode, and one grid, and so on. The first grid, known as the control grid, (and sometimes other grids) transforms the diode into a voltage-controlled device : the voltage applied to the control grid affects the current between the cathode and
12768-414: The plate. When held negative with respect to the cathode, the control grid creates an electric field that repels electrons emitted by the cathode, thus reducing or even stopping the current between cathode and anode. As long as the control grid is negative relative to the cathode, essentially no current flows into it, yet a change of several volts on the control grid is sufficient to make a large difference in
12901-399: The power used by the deflection coil. Von Lieben would later make refinements to triode vacuum tubes. Lee de Forest is credited with inventing the triode tube in 1907 while experimenting to improve his original (diode) Audion . By placing an additional electrode between the filament ( cathode ) and plate (anode), he discovered the ability of the resulting device to amplify signals. As
13034-448: The present-day C cell , for which the letter denotes its size and shape). The C battery's positive terminal was connected to the cathode of the tubes (or "ground" in most circuits) and whose negative terminal supplied this bias voltage to the grids of the tubes. Later circuits, after tubes were made with heaters isolated from their cathodes, used cathode biasing , avoiding the need for a separate negative power supply. For cathode biasing,
13167-521: The problems encountered. Officials there heard that the company was looking for a site for a new plant and offered cheap land, help in improving infrastructure and plentiful local labour. In 1956 Radiotechnique opened a television assembly plant and a factory for electronic components and cathode-ray tubes in Dreux. More than 1,000 workers were to be employed in the new facilities. The workers promised by Dreux, displaced from closed facilities of Grosdemouge, Potez,
13300-523: The professional sector. Under the agreement with Philips the CSF scientific center left Radiotechnique and moved to Levallois as part of the SFR. Roger Julia was replaced by Henri Damelet, an executive who had joined the company in 1924. CSF remained well-represented on the board of directors, and publicity over the transfer of control was avoided. CSF held 70,000 registered shares while Philips held 70,000 bearer shares via
13433-474: The question of thermionic emission and conduction in a vacuum. Consequently, General Electric started producing hard vacuum triodes (which were branded Pliotrons) in 1915. Langmuir patented the hard vacuum triode, but de Forest and AT&T successfully asserted priority and invalidated the patent. Pliotrons were closely followed by the French type ' TM ' and later the English type 'R' which were in widespread use by
13566-459: The research arm Laboratoires d'électronique et de physique appliquée [ fr ] (LEP). RTC was a major manufacturer of photovoltaics and pioneered terrestrial applications as early as 1961. In 1968 Radiotechnique had 30% of the French market for television sets and 50% of the market for picture tubes. As of 1979 RTC was the French components division of Philips Elcoma, and the manufacturer of their solar panels. In 1979 RTC manufactured
13699-651: The rest of the country, Tours is a jumping-off point for tourist visits to the Loire Valley and the royal châteaux . Tours is on one of the main lines of the TGV. It is possible to travel to the west coast of Bordeaux in two and a half hours. From there, the line follows the Mediterranean coast via Avignon , and then to Spain and Barcelona . There are also lines to Lyon , Strasbourg and Lille . It takes less than one hour by train to get from Tours to Paris by TGV and one and
13832-506: The route of pilgrimage to Santiago de Compostela , a major centre during the Middle Ages. In the 6th century, Gregory of Tours , author of the Ten Books of History , restored a cathedral destroyed by a fire in 561. Saint Martin's monastery benefited from its inception, at the very start of the 6th century from patronage and support from the Frankish king, Clovis I , which increased considerably
13965-597: The same time as, for example, the Château de Chenonceau . When the 15th-century illuminator Jean Fouquet was set the task of illuminating Josephus 's Jewish Antiquities , his depiction of Solomon's Temple was modelled on the nearly complete cathedral of Tours. The atmosphere of the Gothic cathedral close permeates Honoré de Balzac 's dark short novel of jealousy and provincial intrigues, Le Curé de Tours ( The Curate of Tours ) and his medieval story Maître Cornélius opens in
14098-589: The same time. In 1849 he started the nightly adoration of the Blessed Sacrament , which spread throughout France. Upon hearing of Sister Marie of St Peter 's reported visions, he started to burn a vigil lamp continuously before a picture of the Holy Face of Jesus . The devotion was eventually approved by Pope Pius XII in 1958 and he formally declared the Feast of the Holy Face of Jesus as Shrove Tuesday (the Tuesday before Ash Wednesday) for all Roman Catholics. The Oratory of
14231-608: The site of one of the most important choral competitions, called Florilège Vocal de Tours International Choir Competition, and is a member city of the European Grand Prix for Choral Singing . The population data in the table and graph below refer to the commune of Tours proper, in its geography at the given years. The commune of Tours absorbed the former commune of Saint-Étienne in 1845 and Sainte-Radegonde-en-Touraine and Saint-Symphorien in 1964. Today, with extensive rail (including TGV ) and autoroute connections linking to
14364-440: The suppressor grid wired internally to the cathode (e.g. EL84/6BQ5) and those with the suppressor grid wired to a separate pin for user access (e.g. 803, 837). An alternative solution for power applications is the beam tetrode or beam power tube , discussed below. Superheterodyne receivers require a local oscillator and mixer , combined in the function of a single pentagrid converter tube. Various alternatives such as using
14497-537: The telephone network and cheap radio receivers, which were popular with the occupying troops. During 1941 and 1942 at least five German directors were installed in the Suresnes factory. By 1944 there were 2,300 workers, with a large proportion of output going to Germany for civilian or military use. After the war Radiotechnique grew fast. Philips acquired total control of Radiotechnique in 1947. The Suresnes factory in 1951 produced half of France's reception tubes and 30–40% of
14630-455: The triode caused early tube audio amplifiers to exhibit harmonic distortion at low volumes. Plotting plate current as a function of applied grid voltage, it was seen that there was a range of grid voltages for which the transfer characteristics were approximately linear. To use this range, a negative bias voltage had to be applied to the grid to position the DC operating point in the linear region. This
14763-407: The triode. De Forest's original device was made with conventional vacuum technology. The vacuum was not a "hard vacuum" but rather left a very small amount of residual gas. The physics behind the device's operation was also not settled. The residual gas would cause a blue glow (visible ionization) when the plate voltage was high (above about 60 volts). In 1912, de Forest and John Stone Stone brought
14896-464: The tube allows the current between the cathode and anode to be controlled by the voltage on the grids. These devices became a key component of electronic circuits for the first half of the twentieth century. They were crucial to the development of radio , television , radar , sound recording and reproduction , long-distance telephone networks, and analog and early digital computers . Although some applications had used earlier technologies such as
15029-638: The tube were much greater. In a sense, these were akin to integrated circuits. In the United States, Cleartron briefly produced the "Multivalve" triple triode for use in the Emerson Baby Grand receiver. This Emerson set also has a single tube socket, but because it uses a four-pin base, the additional element connections are made on a "mezzanine" platform at the top of the tube base. By 1940 multisection tubes had become commonplace. There were constraints, however, due to patents and other licensing considerations (see British Valve Association ). Constraints due to
15162-478: The tubes) without requiring replacement. When triodes were first used in radio transmitters and receivers, it was found that tuned amplification stages had a tendency to oscillate unless their gain was very limited. This was due to the parasitic capacitance between the plate (the amplifier's output) and the control grid (the amplifier's input), known as the Miller capacitance . Eventually the technique of neutralization
15295-410: The use of French in all legal acts, notarized contracts and official legislation to avoid any linguistic confusion. Gregory of Tours wrote in the 6th century that some people in the area could still speak Gaulish . The city has a population of 140,000 and is called "Le Jardin de la France" ("The Garden of France"). There are several parks located within the city. Tours is located between two rivers,
15428-420: The vacuum known as the Edison effect . A second electrode, the anode or plate , will attract those electrons if it is at a more positive voltage. The result is a net flow of electrons from the filament to plate. However, electrons cannot flow in the reverse direction because the plate is not heated and does not emit electrons. The filament has a dual function: it emits electrons when heated; and, together with
15561-421: The voltage applied to the control grid (or simply "grid") was lowered from the cathode's voltage to somewhat more negative voltages, the amount of current from the filament to the plate would be reduced. The negative electrostatic field created by the grid in the vicinity of the cathode would inhibit the passage of emitted electrons and reduce the current to the plate. With the voltage of the grid less than that of
15694-479: The well-known counter-revolutionary chief of Mayenne, was shot in Tours. The arrival of the railway in the 19th century saved the city by making it an important nodal point. The main railway station is known as Tours-Saint-Pierre-des-Corps. At that time, Tours was expanding towards the south into a district known as the Prébendes. The importance of the city as a centre of communications contributed to its revival and, as
15827-556: The west of the Suresnes parent factory. The factory at Suresnes with 2,500 employees was followed by: The Évreux industrial center was located on Rue Pierre Brossolette from 1955, operated by a subsidiary Coprim ( Compagnie des Produits élémentaires pour Industries Modernes ) which mass-produced basic electronic components for mass market devices. By 1959 Radiotechnique had acquired 20% of COGECO, whose factories in Tours and Joué-lès-Tours manufactured capacitors. Dreux gives an example of
15960-427: The wireless telephony receivers. By virtue of its association with Philips it had the financial, technical and commercial resources to enter the television market when it developed in France, and later to enter industrial electronics. This phase was marked by financial restructuring, recruitment and training of managers and technicians, and by geographical expansion of manufacturing facilities. New factories were opened to
16093-437: The workers were foreign-born. Often they lived in primitive conditions in all-male dormitories built by the company. In the early 1950s RT was one of three major vertically integrated tube producers in France, the others being Thomson-CSF and the Compagnie Générale d'Electricité (CGE). In the late 1950s Radiotechnique, Philips and Mullard sold Dario commercial photomultipliers for detection of nuclear radiation, developed by
16226-403: The Évreux plant. The Évreux operation became Aspocomp, a 99% subsidiary of the Aspocomp group. Due to financial troubles the company first announced a severe layoff plan, then went bankrupt. On 20 June 2002 the judicial liquidation of the company Actions Simplifiées Aspocomp was announced by the Évreux District Court and all staff were dismissed. At first the trademark was an R with the outline of
16359-449: Was also technical consultant to Edison-Swan . One of Marconi's needs was for improvement of the detector , a device that extracts information from a modulated radio frequency. Marconi had developed a magnetic detector , which was less responsive to natural sources of radio frequency interference than the coherer , but the magnetic detector only provided an audio frequency signal to a telephone receiver. A reliable detector that could drive
16492-503: Was at this time that the Tours Amphitheatre was built. Tours became a metropolis in the Roman province of Lugdunum towards 380–388 AD, dominating Maine , Brittany, and the Loire Valley . One important figure in the city was Saint Martin of Tours , a bishop who shared his coat with a naked beggar in Amiens . The importance of Martin in the medieval Christian West made Tours, and its position on
16625-515: Was begun about 1170 to replace the cathedral that was burnt out in 1166 during the dispute between Louis VII of France and Henry II of England . The lowermost stages of the western towers belong to the 12th century, but the rest of the west end is in the profusely detailed 15th-century Flamboyant Gothic , which were completed just as the Renaissance was affecting the patrons who planned the châteaux of Touraine. The towers were being constructed at
16758-476: Was built towards 918) and became "Châteauneuf". This space, organized between Saint Martin and the Loire, became the economic centre of Tours. Between these two centres were Varennes, vineyards and fields, little occupied except for the Abbaye Saint-Julien established on the banks of the Loire. The two centres were linked during the 14th century. Tours became the capital of the county of Tours or Touraine ,
16891-405: Was called the idle condition, and the plate current at this point the "idle current". The controlling voltage was superimposed onto the bias voltage, resulting in a linear variation of plate current in response to positive and negative variation of the input voltage around that point. This concept is called grid bias . Many early radio sets had a third battery called the "C battery" (unrelated to
17024-604: Was developed whereby the RF transformer connected to the plate (anode) would include an additional winding in the opposite phase. This winding would be connected back to the grid through a small capacitor, and when properly adjusted would cancel the Miller capacitance. This technique was employed and led to the success of the Neutrodyne radio during the 1920s. However, neutralization required careful adjustment and proved unsatisfactory when used over
17157-444: Was founded and centred on the bank of the Loire in the downtown area, not, as was the current practice, in a campus in the suburbs. The latter solution was also chosen by the twin university of Orleans. Royer's long term as mayor was, however, not without controversy, as is exemplified by the construction of the practical but aesthetically unattractive motorway, which runs along the bed of a former canal just 1,500 metres (4,900 feet) from
17290-609: Was sold in 1998 and went bankrupt in 2002. The Compagnie générale de la télégraphie sans fil (CSF) was formed in 1919 as a holding company for the Société française radio-électrique and other subsidiaries in fields related to radio-electricity. Radiotechnique was initially based in Lyon in 1919. The Radiotechnique subsidiary of the CSF was formed in 1919 to research and develop electronic transmission and reception tubes. In 1921 Radiotechnique began to make radio sets at its Suresnes factory. During
17423-662: Was the first city of the silk industry. It was taken by Louis XI , as the royal capital under the Valois Kings with its Loire castles and city of art with the School of Tours. The prefecture was partially destroyed during the French Wars of Religion in the late 16th century and again during the Second World War in June 1940. The White and Blue city keeps a historical center registered in
17556-479: Was transferred to Radiotechnique and then to Philips in 1931. It gradually became a sub-brand of the Philips group before disappearing in 2002. Vacuum tube A vacuum tube , electron tube , valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as
17689-401: Was usually connected to the cathode and its negative voltage relative to the anode repelled secondary electrons so that they would be collected by the anode instead of the screen grid. The term pentode means the tube has five electrodes. The pentode was invented in 1926 by Bernard D. H. Tellegen and became generally favored over the simple tetrode. Pentodes are made in two classes: those with
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