Television

University of PitestiDolnośląska Wyższa Szkoła Przedsiębiorczości i Techniki w

Polkowicach

Dobrica Adrian

Dr inż. ZDZISŁAW PÓLKOWSKI

Polkowice, 2015

• Definition• History• Color Television• The Social Impact of Television

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Old Tv

Nowadays TV

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Definition

The system or process of producing on a distant screen a series oftransient visible images, usually with an accompanying sound signal.Electrical signals, converted from optical images by a camera tube, aretransmitted by UHF or VHF radio waves or by cable and reconvertedinto optical images by means of a television tube inside a television set . A Television, commonly referred to as TV or Tele is a telecommunication medium used for transmitting sound with moving images in monochrome (black-and-white), colour, or in three dimensions. It can refer to a television set, a television program, or the medium of television transmission. Television is a mass medium, for entertainment, advertising and news.

http://dictionary.reference.com/browse/television

http://en.wikipedia.org/wiki/Television

• The word television was coined at the World Fair in 1900. The history of the idea for television is actually older than the history of television itself. George Carey, a Boston civil servant, was thinking about television systems in 1876, and in 1877 he made drawings of a "selenium camera" to allow people to "see by electricity." Others were also bringing forth thoughts and experimenting with ideas that would lead to the invention of the television. Some think that the original reason for the television was to be used as what we know as a videophone.

• Paul Nipkow proposed and patented the first electromechanical television system in 1884, but he could not develop a system that worked. In 1925, the first publicly demonstrated working system in the history of television, created by John Logie Bard, displayed a moving silhouette. In 1928, Baird broadcasted the first transatlantic signal and the first regularly scheduled television service began, and in 1931, the first live transmission was made. 

History

http://www.historyinfo.org/history-of-television.php

• The first fully electronic set in the history of television was created in 1927 by Philo Taylor Farnsworth, but it wasn’t until 1934 that he created one that worked well.

• The first color transmission was demonstrated by Baird in 1928, and the first color transmission of the electronically scanned era in 1940. Color television field tests began in 1941, but because of World War II and other circumstances, the first color broadcast to the public did not occur until 1951. It was in the 1966-1967 season that the networks began broadcasting in full color for prime time television.

• The history of television continues to advance even today. From it’s invention, it has gotten bigger and bigger, of better quality, and more popular. Ninety-eight percent of homes in America had at least one television by the late 1980’s.

http://www.historyinfo.org/history-of-television.php

• One of the great electrical engineering triumphs was the

development of color television in such a way that it remained

compatible with black and white television.

• A major driving force behind the majority of current color TV

standards was to allow black-and-white TVs to continue to be

able to receive a valid TV signal after color service was in

place.

http://electronicaupit.com/forum/index.php?board=13.0

Color Television

Trireceptor theory of vision

why we use RGB monitors

• If you ask someone why red, green and blue are used in

computer monitors -- the immediate answer is "Because these

are the primary colors".

• If you then ask, "But why are these the primary colors?" -- the

answer you get is that "If you mix light of these colors together

you can make any color".

http://electronicaupit.com/forum/index.php?board=13.0

http://electronicaupit.com/forum/index.php?board=13.0

Color information transmission in TV

• In the most basic form, color television could simply be implemented by having cameras with three filters (red, green and blue) and then transmitting the three color signals over wires to a receiver with three electron guns and three drive circuits.

• Unfortunately, this idealized view is not compatible with the previously allocated 6 MHz bandwidth of a TV channel. It is also not compatible with previously existing monochrome receivers.

http://electronicaupit.com/forum/index.php?board=13.0

• Therefore, modern color TV is carefully structured to preserve all the original monochrome information -- and just add on the color information on top.

• To do this, one signal, called luminance (Y) has been chosen to occupy the major portion (0-4 MHz) of the channel. Y contains the brightness information and the detail. Y is the monochrome TV signal.

• Consider the model of a scene being filmed with three cameras. One camera has a red filter, one camera a green filter and one camera a blue filter.

http://electronicaupit.com/forum/index.php?board=13.0

• Assume that the cameras all adjusted so that when pointed at "white" they each give equal voltages. To create the Y signal, the red, green and blue inputs to the Y signal must be balanced to compensate for the color perception misbalance of the eye.

• The governing equation is:

• For example, in order to produce "White" light to the human

observer there needs to be 11 % blue, 30 % red and 59%

green (=100%).

http://electronicaupit.com/forum/index.php?board=13.0

Multiplexing of Luminance and Chrominance

• Position the bandlimited chrominance at the high end of the luminance spectrum, where the luminance is weak, but still sufficiently lower than the audio (at 4.5 MHz).

• The two chrominance components (I and Q) are multiplexed onto the same sub- carrier using QAM.

• The resulting video signal including the baseband luminance signal plus the chrominance components modulated to f c is called composite video signal.

http://electronicaupit.com/forum/index.php?board=13.0

www.astrology.co.uk

Television is a "window on the world" for news and information. 

• We previously noted that many social problems are only acted up after they are reported on television.

• Newspapers and the print media provide a degree of separation from reality, but TV graphically brings happenings right into living rooms, complete with color, sound, time sequences, and even to some degree, the associated "feelings."

The Social Impact of Television

http://www.cybercollege.com/frtv/frtv034.htm

Television provides needed escape and relaxation

• To a great extent we've already discussed this inprevious modules.

• Suffice it to say, television allows us to momentarily escape our problems and experience the experiences of other people.

• We can become awestruck with the beauty of and grace of the arts, or caught up in the frenzy and excitement of an athletic event. We can even allow ourselves to be momentarily lost in a beautiful fantasy world.

http://www.cybercollege.com/frtv/frtv034.htm

Television introduces new ideas and information

• Before the mass media, an important threat to health, a new medicine, or improved ways of doing things could take months or even years to become commonly known.

• Today, that time is typically cut down to a day -- or even a few hours.

• Included in this category are new products and services that will make our life easier or safer, new recipes, important safety procedures, and even instructions on home improvement and repair.

http://www.cybercollege.com/frtv/frtv034.htm