Television set

A television set (commonly called TV or telly) is a device for receiving and displaying television signals. To this end, it is adapted for receipt of the television signal and display of the belonging to the picture sound, but additionally provided with a display screen with associated control electronics for the display of visual information: the television picture. For a long time the display screen a picture tube of a television set, acathode-ray tube designed specifically for displaying television pictures. Today almost all televisions produced are equipped with LCD - andplasma screens for the display.



Content
*1 History  ==History [  edit ] == A television in 1958.The development of the television set was initially along two different lines: a rested according to both mechanical and electronic principles and which in a second purely electronic principles. The latter line all modern televisions are derived, but this would not have been possible without discoveries and insights from the mechanical systems and originated in America. ===Mechanical line [the  Nipkow disk edit ]  === The electromechanical television that Paul Gottlieb Nipkow developed and patented in 1884 was the basis of this, the Nipkow disk . In this rapidly rotating flat disc were small holes arranged in a spiral pattern. The light and dark areas was washed with the aid of a photocell (selenium-cells) is converted into an electrical signal. This started a neon lamp in the same sequence of light and dark the picture via a second synchronized rotating disk projected on a screen. It took until 1907 before the developments of the reinforcement tube technology made the design practical.
 * 1.1 Mechanical line: the Nipkow disk
 * 1.2 The electronic television
 * 2 Technology
 * 2.1 Imaging performance
 * 2.2 Electron Beam
 * 2.3 Synchronization
 * 2.4 Color
 * 2.5 Modulation
 * 2.6 Teletext
 * 2.7 Sound
 * 2.8   Digitization

In the period 1907-1910, showed Boris Rosing and his student Vladimir Zworykin a television system to the outside world with a mechanical mirror-drum scanner, and a cathode-ray tube in the receiver. This cathode-ray tube, an invention of Karl Ferdinand Braun in 1897, is a glass vacuum tube in which with the aid of an electron beam on the fluorescent end the image is projected. Rosing disappeared during the revolution of 1917, but Zworykin later went to RCA working to build a genuine electronic television.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">A semi-mechanical analogue television system was first shown in London in February 1924 by John Logie Baird with a picture of Felix the Cat and a moving image by Baird on 30 October 1925. The company (Baird Television Development Company) realized in 1928 the first transatlantic signal of the television between London and New York.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">In 1932, Baird introduced the VHF television . The Baird system was approved by the BBC, which ended this practice in 1937 in favor of purely electronic television. ===The electronic TV <span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Although the discoveries of Nipkow, Rosing, Baird and others were exceedingly little is their technology used in modern television. By 1934 all were electromechanical television systems obsolete.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Already in 1908, the Briton had AA Campbell Swinton describes the concept of an electronic television system that uses the cathode ray tube invented by Karl Ferdinand Braun . He proposed to use an electron beam in both the camera and the receiver. His system was never built.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">A fully electronic system was first shown by Philo Taylor Farnsworth in the fall of 1927. Farnsworth, a Mormon farm boy from Rigby, Idaho, made ​​its first system at the age of 14 years. He discussed the idea with his teacher, who could think of no reason why the system would not work (Farnsworth would later credit this teacher, Justin Tolman, as providing key insights into his invention). He kept the idea at Brigham Young Academy (now Brigham Young University) pursue. At the age of 21, he showed an operating system to its own laboratory in San Francisco.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">His breakthrough television freed from its dependence on spinning disks and other mechanical parts. All modern TVs of the tube are directly derived from its design. Russian Vladimir Zworykin is sometimes cited as the father of electronic television for his invention of the iconoscope in 1923 and his invention of kinescope in 1929; his design was one of the first to a television system with all the properties of modern picture tubes.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">About the controversy on a first (Farnsworth or Zworykin) invented the modern television has yet to be debated on this day. ==<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;font-family:sans-serif;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Technology  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] == <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">A flow of electrons is generated in the back of the display tube, and focused on the inside of the display screen. The device is called the electron gun . A very high voltage is placed on the inner side of the screen, between 15,000 and 25,000 volts. This voltage causes the electrons reach a high speed if they encounter no obstacles such as gas molecules. In order to prevent that due to collisions with these obstacles too much heat is generated, the display tube is sucked as far as possible vacuum. The pressure differential between the exterior and interior of the display tube is almost 1 kg per square centimeter. The glass is very thick to withstand this pressure. The electrons hit a phosphor layer, and the spot indicates that layer thereby visible light. ===<span class="mw-editsection-bracket" style="color:rgb(85,85,85);"><span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;">[Image  Structure <span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;">edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">]  === Widescreen device.<p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">In the European television system, the picture is 625 lines written on the screen, from the left to the right (seen from outside). The lines are written from top to bottom, first the odd lines. Thereafter, the even lines are written in between. Because the light from the phosphorescent layer is extinguished quickly, this gives a smoother image than when all the lines were to be written in order. This whole (odd + image) is repeated 25 times per second. The received video signal contains the luminance (between black and white) of each image point, but also a sudden signal change to indicate the beginning of each line. The first few lines of each image are black, and this is usually different from the rest of the image. ===Electron beam <span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">For the electron beam in the display tube to be moving in this diffractive pattern of lines across the screen flushing used. These include the electron gun in the rear of the display tube. To control these two deflection signal generators required. The first signal generator is the line of oscillator 15625 Hz for the lines (25 × 625 = 15625). The second signal generator is the grid oscillator of 50 Hz for the images. It is no coincidence that for 50 Hz (25 frames per second) is selected in countries where the frequency of the voltage is 50 Hz. Interference from the mains (mains hum) is easier to keep out of the picture. In countries including the United States, with a frequency of 60 Hz, one uses for the same reason 30 frames per second. ===<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Synchronization  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The Field and line oscillator are set too slow, and therefore it will become slightly behind compared to the transmitter. This gives the opportunity to the oscillator by means of a control signal to run in synchronism with the transmitter. The above-described "anomalies" in the video signal display synchronizing them for this. (In modern circuits used a different method of synchronization.) ===<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Color  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">In a color TV, there are three electron guns at the back of the display tube, initially disposed in a triangle (viewed from the front), but later next to each other (in-line display tube). Directly behind the front of the picture tube is placed a grating, the so-called shadow mask. Each electron gun may affect only dots on the screen in front of the own color, in that the three beams at a different angle to go through the same holes of the grid. There are phosphors that light used in each of the primary colors red, green and blue. Through a combination of brightness of the three colors, any desired color can be displayed.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">A Sony invention, the so-called Trinitron picture tube, includes a louvered grate in place of the shadow mask, causing less loss of the electron beam, which results in a brighter image. ===<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Modulation  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The video signal ( black and white ) in restzijbandmodulatie, a form of amplitude modulation broadcast. The modulation is negative, a stronger signal indicates more black. In the PAL Color Engine, the color information by the sender in a separate color subcarrier transmitted between picture and sound. The color auxiliary signal is transmitted in a complicated manner (quadrature ). Here, the carrier wave is suppressed as much as possible. In the receiver, a separate oscillator is required to restore this signal. Their synchronization is synchronized with a burst signal is sent with the image synchronization signals. A black-and-white receiver is not adapted to the detection of the color signal, but is not affected by it.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Due to the quadrature modulation to the color auxiliary signal may contain two signal components at the same time, in which the colors red and blue are recorded (the color difference signals). For example, are available at any time:

<p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">With this information, the missing color green can be traced back, in that the sum of the three colors is equal to the black-and-white signal. Where the two color signals lack a white or gray image is displayed.
 * black and white (brightness)
 * red
 * blue

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The emitted color is incorporated into the phase of the color sub-signal and is relatively sensitive to variations in the transfer. In the American NTSC-system, therefore, it was in the past, in order to set the color itself. The Western European PAL system on the other hand features a built-in correction. One of the two color signals is switched to the transmitter per picture line to-and-over and put back into the receiver. Due to the last operation, the color information of each image line to means with those of the foregoing, the color error is compensated. For this it is necessary to store the color information in a delay line during the time that it takes (64 mS ) in order to write one picture line on the screen. ===Teletext <span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">In the black lines between successive images can also be transmitted digital information, such as station identification, program name, and teletext . To do this, the receiver is required than in a memory and a character former. To show this latter makes it possible letters and characters from this memory on the screen. ===Sound <span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Finally, there is also the sound. The operation of this is similar to that in a stereo FM radio receiver. The portion of the television receiver typically selects one of the channels and at the same time the corresponding color-sub-carrier signal and the associated audio signal. ===<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Digitization  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Modern color televisions write the received image first in a digital memory, and then write it to the screen. This makes it possible to write each image twice in the time that one image is received (100Hz-TV). Due to the rapid repetition of the picture is the fact, quickly being phased fluorescent screens, less tiring for the viewer.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Also, now, for example, ¼ of the screen, the image from another source are displayed in smaller size ( picture-in-picture or PIP). The rest of the screen shows at the same time the "normal" image. This other source can be for example a video recorder, or a computer. Furthermore, it is possible comprehensive image processing, such as the magnified view of a portion of the transmitted image, or to store and then display next to each other on a number of still images from the broadcast (snapshot).