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Television
Television is a system for transmitting and receiving moving images and sound to distance. This transmission can be effected by means of radio[->0] waves[->1] or by specialised networks of cable television[->2]. The receiver[->3] of signals is the television[->4].
The word "television" is a hybrid of Greek voice "tele" (distance[->5]) and the Latin "visio" (vision[->6]). The termtelevision refers to all aspects of television programming and transmission. It is sometimes abbreviated as TV. This term was first used in 1900[->7] by Constantin Perski in the International electricity Congress in Paris[->8] (CIEP).
The world television day is celebrated on 21 November[->9] in commemoration of the date on which the first World Television Forum at the United Nations[->10]was heldin 1996[->11].
History
Main article: History of television[->12] The concept of television (distance vision) can be traced to his telescope[->13]and Galileo galilei[->14] . However, it is not until 1884, with the invention of the Nipkow disk[->15] of paul nipkow[->16] when significant progress was made to create an environment. The change that would bring the television as we know today was theinvention of the iconoscope[->17] of vladimir zworkyn[->18] and philo Taylor farnsworth[->19]. This would give step to fully electronic television, which had a much better refresh rate, higher definition image and own lighting.
First developments In 1910[->20], the Nipkow disk was used in the development of systems of television of the beginning of the 20th century[->21] , in 1925[->22] theScottish inventor john logie baird[->23] performs the first actual experience using two discs, the emitter and the receiver, which were attached to the same axis so that their rotation was synchronous and separated by 2 mm.
The first public television broadcasts made the BBC[->24] in England[->25] in 1927[->26] and the CBS[->27] and NBC[->28] in United States[->29] in 1930[->30]. Mechanical systemswere used in both cases and programmes were not issued with a regular schedule.
Emissions with programming began in England[->31] in 1936[->32], and United States[->33] on April 30, 1939[->34], coinciding with the inauguration of the Exposition[->35] of New York[->36]. The scheduled broadcasts were discontinued during the World War II[->37], resuming when it ended.
Electronic television
In1937[->38] began regular broadcasts of TV e[->39] in France[->40] and United Kingdom[->41]. This led to a rapid development[->42] of the television industry and to a rapid increase in viewers, although television sets were very expensive, small screen[->43] . These broadcasts were made possible by the development of the following elements at each end of the chain: the cathode ray tube[->44] andiconoscope[->45]
The video signal
Main article: Video signal[->46] Signal transducing the image contains the information on this, but it is necessary for their restructuring, which has a perfect synchronism between the deflection of exploration and the deflection in the representation.
The exploration of an image is carried out through its decay, first in frames which are called frames and then inlines, reading each frame. To determine the number of required frames so that you can put together a moving image as well as the number of lines to obtain an optimum quality in reproduction and the optimum perception of the color (in the colour TV) were conducted numerous empirical and scientific studies of the human eye and its way of perceiving. He was that the number of frames must be at leastof 24 per second (then they were used for other reasons 25 and 30) and that the number of lines must be greater than the 300.
The video signal it is composed the information of the image corresponding to each line (the PAL[->47] 625 system lines and the 525 NTSC[->48] for each table) grouped into two groups, the odd lines and the pairs of each table, each of these groups of lines are called...