Monday, December 1, 2014

TELEVISION



We all are very well familiar with the word ‘Television’ in our life. Now-a-days it is very popularly called as ‘Idiot Box’. We can’t imagine living without television. In our busy life schedules, it is a good source of entertainment for all age groups. Also it plays an important role in advertising and marketing.

But we must not be familiar with the history of television that how it was invented and how its evolution has today reached to the LED TVs.Let’s have a brief over this.


After the invention of telephone in 1878, the idea of transmission of images in motion through electric signals was firstly sketched as telephonoscope. At the time, it was imagined that someday light could be transmitted over copper wires as sounds was transmitted through telephone.


In 1881, process of scanning was used to transmit images practically in the pantelegraph through the use of a pendulum -based scanning mechanism. From then, scanning in one form or another has been used for converting a visual image into electric pulses for transmission. This process is called as "rasterization".

In 1883, Discovery of the property of selenium that the electrical resistance of selenium varies with light; created the technical possibility that pictures could be translated into electrical signals.

In 1884, Paul Gottlieb Nipkow, a 23-year old student in Germany, developed the first ever mechanical module of television. He used a scanning disk that was spinning with a series of holes towards the center, for rasterization. Spacing between the holes at equal angular intervals was such that, in a single rotation, the disk would allow light to pass through each hole and onto light-sensitive selenium sensor which produced the electrical signals. Each hole captured a horizontal slice of the entire image. This technology was known as the ‘electric telescope’ that had 18 lines of resolution but moving images were still not possible due to the poor sensitivity of the selenium sensors.

In 1897, the Cathode Ray Tube (CRT) was developed and improvements were made in amplifying the electrical signals. But due to the slow reaction of selenium to light, it was quite difficult to transmit changing images.

In 1907, A.A. Campbell-Swinton from England and Russian scientist Boris Rosing became the first inventor to use a CRT to receive electrical signals of an experimental television system. He used mirror-drum scanning to transmit simple geometric shapes to the CRT.

In 1923, an American inventor, Charles Jenkins used the Nipkow’s disk idea to invent the first ever practical mechanical television system. By 1931, his Radiovisor Model 100 was being sold in a complete kit as a mechanical television.


But still the task of achieving the speed and coordination between transmitter and receiver to broadcast moving pictures was difficult.

In 1926, a Scottish inventor, John Logie Baird was the first person succeeded in transmitting moving monochromatic images through the mechanical disk system started by Nipkow. Baird's scanning disk produced an image of 30 lines resolution, just enough to discern a human face.

In 1926, also an Hungarian engineer designed a television system based on fully electronic scanning and display elements and used the principle of "charge storage" within the scanning tube.


On 25 December 1926, Takayanagi demonstrated a TV system with a 40-line resolution that employed a CRT display in Japan. This was the first working example of a fully electronic television receiver.

By 1927, Russian inventor Léon Theremin developed a mirror-drum-based system which used interlacing to achieve an image resolution of 100 lines.

In 1927, Philo Taylor Farnsworth was able to invent a working model of electronic television that was based on Swinton’s idea to use CRT for electronic television.

In 1927, Baird also invented the world's first video recording system,"Phonovision;" because the signal produced by his 30-line equipment was in the audio frequency range, he was able to capture it on 10-inch gramophone records using conventional audio recording technology.

In 1928, there were about 15 American television stations. The pictures used for broadcasting were mostly experimental. But in 1933, because of poor picture quality they disappeared. The need for an adequate scanning system was necessary

In 1930, Zworykin and Philo Farnsworth made advancements. Farnsworth came up with a system that could transmit only bright pictures but incorporated elements of a superior scanning system.

In 1931, Despite decades of effort, there was a limit to how rapidly a mechanical scanner could work. The television in 1930 was fuzzy. It was estimated that 7 million pictures per second need to be transmitted for good quality.


At the Berlin Radio Show in August 1931, Manfred von Ardenne gave the world's first public demonstration of a TV system using a cathode ray tube for both transmission and reception. The world's first electronically scanned TV service began in Berlin in 1935. In August 1936, the Olympic Games in Berlin were carried by cable to TV stations in Berlin and Leipzig where the public could view the games live.

In 1935, the German firm and the United States firm Farnsworth Television owned by Philo Farnsworth signed an agreement to exchange their television patents and technology to speed development of TV transmitters and stations in their respective countries.

On 2 November 1936, the BBC (British Broadcasting Corporation) began transmitting the world's first public regular high-definition service from the Victorian Alexandra Palace in north London. It therefore claims to be the birthplace of TV broadcasting as we know it today. In 1941, The Federal Communications Commission settled on the 525 line screen, 30 frames per second, and 6 megahertz band width standard that is in use today for government regulation standards. 30 stations were licensed but World War II delayed the spread of television. But still there was broadcasting of black and white images only, no colored images.

Color broadcast can be created by broadcasting three monochrome images, one each in the three colors of red, green and blue (RGB). When displayed together or in either rapid succession or optically overlapped, these images will blend together to produce a full color image as seen by the viewer.

One of the great technical challenges in broadcasting colored images was the desire to conserve bandwidth potentially three times that of the existing black-and-white standards and not use an excessive amount of radio spectrum.

Although all-electronic color was introduced in the US in 1953 but the first national color broadcast (the 1954 Tournament of Roses Parade) occurred on January 1, 1954. It was not until the mid-1960s that color sets started selling in large numbers, due in part to the color transition of 1965 in which it was announced that over half of all network prime-time programming would be broadcast in color that fall. The first all-color prime-time season came just one year later.



Early color sets were either floor-standing console models or tabletop versions nearly as bulky and heavy.The introduction of GE's relatively compact and lightweight Porta-Color set in the spring of 1966 made watching color television a more flexible and convenient proposition. In 1972, sales of color sets finally surpassed sales of black-and-white sets. Also in 1972, the last holdout among daytime network programs converted to color, resulting in the first completely all-color network season.

Color broadcasting in Europe was not standardized on the PAL format until the 1960s, and broadcasts did not start until 1967. By this point many of the technical problems in the early sets had been worked out, and the spread of color sets in Europe was fairly rapid.

By the mid-1970s, the only stations broadcasting in black-and-white were a few high-numbered UHF stations in small markets and a handful of low-power repeater stations in even smaller markets such as vacation spots. By 1979, even the last of these had converted to color, and by the early 1980s B&W sets had been pushed into niche markets, notably low-power uses, small portable sets, or use as video monitor screens in lower-cost consumer equipment in the television production and post-production industry.

As we move on from black and white televisions to colored televisions, now the time has moved on also. Television has become so compact,sleek and thin with more added features like woofer and high definition LED TVs that create a cinema hall like feeling in the house.













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