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A television is an electronic device destined for the receipt and reproduction of signs of television. Usually it consists of a screen and controls or controls. The word comes from the Greek TV (far) and Latin visor ("to 'see"). It was created On January 26, 1926 by John Logie Baird.
His functioning is based on the phenomenon of the photoelectricity, which is the person in charge of the transformation of the light in electrical current in a chamber that can be transmitted by waves of high frequency up to the antennas of receipt and to be reproduced on the screen of our televisions. The television is one of the devices of more daily use.
The interior of a device of television can divide basically in two big parts. The first group
It would be constituted by the elements dedicated to the receipt of the sign and the second block would be compound
For those elements that are busy with happening the image. Really, the device of television, named simply television, should be called a recipient of television, since it is a question of a device capable to receive a sign which content is that of an image produced distantly.
First, we are going to see how the image takes place, later, to go on to the receipt of the above mentioned image across signs of radio.
PRODUCTION OF THE IMAGE
The image in a television is produced by what we call "cathode-ray tube" (T.R.C). This element
It was created a long before the invention of the television and, undoubtedly, it is a fundamental piece of the television
Beside constituting one of the principal elements of this one, since it influences in a basic way in
The size, in the form and in the price of the device (1 appears).
The cathode-ray tube is formed basically by four elements.
First there is a " issuer of electrons ". East
Element is constituted, in general, by a hollow cylinder of nickel covered in one of his ends by issuing substances of electrons, such as oxide of barium and strontium.
An issuing substance of electrons is a substance that to
Warming up sufficiently is capable of expelling electrons, something like " tiny bomb " that it was exploiting constant and throwing electrons in all directions while it is kept warm.
On having had cylindrical form, a species of effect is obtained cannon since only they go out towards was those
Electrons that go in the direction at that the issuer of electrons aims.
Of there that this device also is known by the name of cannon of electrons.
As soon as the electrons have worked out dismissed of his issuer they meet a " accelerator of electrons " which they stamps a still major speed of which they had
On having been issued. The accelerator of electrons consists simply of two sufficiently distant plates
The television has advanced very much in the last years, initially only they existed in black and white and later the television got in color. Nowadays there continues being improved the quality of the image and of the sound applying all the advances of the electronics, as the integrated circuits, in the devices of television.
To be able to transmit an image in movement, the whole process must be completed by the time of persistence of the image in the retina of the eye, that is to say, in less than one tenth of second. Therefore, the bundle of electrons will have to analyze immediately the image with his movement of " it goes and comes " horizontal, by means of a series of lines Standard. To major quantity of lines, the definition of the image is better.
According to the European Standard, the image has 625 lines, to 25 per second. Already we have come to the TV of high definition (HDTV) with the image of 1250 lines, 50 per second.
Nowadays, three systems of transmission exist in color: the American NTSC, adopted also as Japan , this Asian and South America; the PAL (Germany , Australia , Italy ...) and the SECAM (adopted as France , Russia
The introduction of the satellites for the telecommunications has offered the possibility of radiating a television transmission thrown to the satellite from a station of item to the receiving aerials of the whole planet. The satellites divide in three groups, which three successive generations represent: satellites from point to point, destined to the international connections; of distribution, which they can serve at the same time to several television stations; of direct diffusion, which there issue signs caught directly by every television.
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