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How it all began?
Who invented the television? It would be difficult to pinpoint a single
person as the inventor of the modern day television, which has
virtually brought world happenings to our homes. The story of the
evolution of the television began in the nineteenth century, in the
year 1817 to be precise, with the discovery of the chemical element
selenium, introduced to the world by a Swedish chemist, Jons
Berzelius.
Later scientists found that the amount of
electric current selenium would carry depended upon the amount of
light that struck it. This property came to be known as "photoelectricity"
and it led, in 1875, to the making of the first crude television
system by an American inventor, G.R. Carey. He found that as a
scene or an object was focused through a lens onto a bank of
photoelectric cells, each cell would control the amount of
electricity it would pass on to a light bulb. Crude outlines of the
object would then show in the lights. |
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The first practical transmission of
pictures over wires came in 1923, with John Logie Baird of Scotland
and Jenkins of the United States being the ones to accomplish the
task. Baird used a rotating disc with holes in it to transform the
scene into a series of lines. A photo electric cell converted the
varying intensity of light into electrical signals. These electrical
signals were then fed to a bulb. The intensity of light emitted by
the bulb flickered with changes in the strength of the electric
current. Another rotating disc was kept in front of this bulb. A
faint image was obtained through this rotating disc which
corresponded to the original scene. Since then a lot of
development was seen in the sphere of television as well as
television cameras.
Color televisions, that we take for
granted, were introduced to the world by Baird in the year 1928.
However it was only in late 1953 that the first successful color
television system was adopted for broadcasting. Color reproduction
for television is the same as is being done for color photography
or color printing - the same principle of mixing the colors red,
green and blue in appropriate proportions is used. In the case of
color television, the receiver reproduces the colors red, green,
and blue (primary colors in paints are different, they are red,
yellow and blue).
The world's first public
television service was started from the BBC station at Alexandra
Palace in London, on November 2, 1936.
How Does a TV Work?
How Television Works?
TV signals broadcasted from a
transmission tower are picked up by an antenna. The antenna converts
the electromagnetic signal into an electrical signal. A cable
connected to the antenna feeds this signal to a TV receiver. In the
receiver the signal is first fed to a tuner, the tuner selects the
TV channel and separates the audio, video and synchronizing signals
which are then strengthened. The next circuit separates the video
signal into three color signals, viz. red, green and blue. This
circuit also controls the strength of the three color signals.
These color signals are then fed to an electron gun each.
Each electron gun produces one color, red , green or blue. The
electrons travel towards the TV screen. Before reaching the TV
screen this beam of electrons is deflected by powerful electro
magnets which receive the synchronizing signals from the
synchronizing circuit. The synchronizing signal determines the
movement of the electron beams across the TV screen. Both a vertical
and a horizontal synchronizing signal is fed to the electromagnets.
Consequently the electron beams hit precise points on the TV screen.
The TV screen is covered in microscopic dots of phosphors. These
phosphors glow when the electrons hit the screen and consequently a
picture can be seen on the screen. |
