7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 1/34

  COMILLA

UNIVERSITY 

DEPARTMENT

OF 

INFORMATION AND COMMUNICATION

TECHNOLOGY(ICT)

 

COURSE LEADER’S NAME: KHONDOKAR FIDA

HASAN

AUTHORS’S NAMES:

1.MD.NATIK ALAM BHUYAN TAHSIN 2. AFTABUR

RAHMAN PARVEZ

ID NO:1109028 ID

NO:1109015

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 2/34

 

COMILLA UNIVERSITY 

DEPARTMENT

  OF

INFORMATION AND COMUNICATION

TECHNOLOGY(ICT)

COURSE LEADER’S NAME: KHONDOKAR FIDA

HASAN

E-MAIL: k.fidahasan@yahoo.com

AUTHORS’S NAMES: 1.MD. NATIK ALAM BHUYAN

TAHSIN

  ID NO: 1109028

2.AFTABUR RAHMAN

PARVEZ

2 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 3/34

  ID NO : 1109015

E-MAIL: 1. tahsinnatikalam@yahoo.com

2. Aftabur.parvez@gmail.com

DATE OF SUBMISSION: 25 APRIL,2012.

 

TABLE OF CONTENT

INTRUDUCTION………………………………………………

…………….. 4

HISTORY OF

TELEVISION………………………………………………. 5

3 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 4/34

GEOGRAPHICAL USAGE

………………………………………………...1O

ELEMENTS OF A TELEVISION SYSTEM…………………………..11

DISPLAY TECHNOLOGY…………………………………....

……………13

HOW TELEVISION

WORKS…………………………………………….15 HOW CRT TELEVISION

WORKS…………………………………..15

HOW PLASMA TELEVISION

WORKS……………………………17

RECEVING SIGNALS FOR

TELEVISION………………………….19 EXTRACTING THE

SOUND………………………………………….19

STRUCTURE OF A VIDEO

SIGNAL………………………………..20

MONOCHROME VIDEO SIGNAL

EXTRACTION……………..22

COLOR VIDEO SIGNAL

EXTRACTION……………………………22

4 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 5/34

SYNCHRONIZATION……………………………………………

……..25

HORIZONTAL

SYNCHRONIZATION………………………………25

VERTICAL

SYNCHRONIZATION……………………………………26

HORIZONTAL HOLD AND VERTICAL

HOLD………………….27

CONCLUSION………………………………………………...………………28

BIBILOGRAPHY……………………………………………..

……………..29

APPENDIX………………………………………………………

…………………….30

INTRUDUCTION

 Television (TV) is a telecommunication medium for transmittingand receiving moving images that can be monochrome (black-

and-white) or colored, with or without accompanying sound.

"Television" may also refer specifically to a television set, television

programming, or television transmission.

5 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 6/34

The etymology of the word has a mixed Latin and Greek origin, meaning "far 

sight": Greek tele (τ λε), far, and Latin visio, sight (from video, vis- to see, or to

view in the first person).

Commercially available since the late 1920s, the television set

has become commonplace in homes, businesses and institutions,particularly as a vehicle for advertising, a source of entertainment, and news. Since the 1970s the availability of videocassettes, laserdiscs, DVDs and now Blu-ray Discs, have resulted inthe television set frequently being used for viewing recorded aswell as broadcast material. In recent years Internet television hasseen the rise of television available via the Internet, e.g. iPlayer and Hulu.

Although other forms such as closed-circuit television (CCTV) are

in use, the most common usage of the medium is for broadcasttelevision, which was modeled on the existing radio broadcasting systems developed in the 1920s, and uses high-powered radio-frequency transmitters to broadcast the television signal to individual

TV receivers.

 The broadcast television system is typically disseminated viaradio transmissions on designated channels in the 54–890 MHz frequency band.[1] Signals are now often transmitted with stereo or surround sound in many countries. Until the 2000s broadcast

 TV programs were generally transmitted as an analog television signal, but in 2008 the USA went almost exclusively digital.

A standard television set comprises multiple internal electroniccircuits, including those for receiving and decoding broadcastsignals. A visual display device which lacks a tuner is properlycalled a video monitor, rather than a television. A televisionsystem may use different technical standards such as digitaltelevision (DTV) and high-definition television (HDTV). Televisionsystems are also used for surveillance, industrial process control, and

guiding of weapons, in places where direct observation is difficult or dangerous.By 2012 the development of broadband enabled the integration of the internet and Web 2.0 features into modern television sets andset-top boxes, as well as the technological convergence betweencomputers and television. Such TVs are called smart TV's or"connected TV", which is the biggest current innovation in consumer 

electronics.

6 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 7/34

HISTORY OF TELEVISION

In its early stages of development, television employed a combination of optical,mechanical and electronic technologies to capture, transmit and display a visual

image. By the late 1920s, however, those employing only optical and electronic

technologies were being explored. All modern television systems relied on the

latter, although the knowledge gained from the work on electromechanical systems

was crucial in the development of fully electronic television.

  Braun HF 1 television receiver, Germany, 1958

The first images transmitted electrically were sent by early mechanical fax machines, including the pantelegraph, developed in the latenineteenth century. The concept of electrically powered transmission of 

television images in motion was first sketched in 1878 as the telephonoscope,

shortly after the invention of the telephone. At the time, it was imagined by early

science fiction authors, that someday that light could be transmitted over copper 

wires, as sounds were.

 The idea of using scanning to transmit images was put to actualpractical use in 1881 in the pantelegraph, through the use of apendulum-based scanning mechanism. From this period forward, scanning

7 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 8/34

in one form or another has been used in nearly every image transmission

technology to date, including television. This is the concept of "rasterization", the process of converting a visual image into astream of electrical pulses.

In 1884 Paul Gottlieb Nipkow, a 23-year-old university student inGermany, patented the first electromechanical television systemwhich employed a scanning disk, a spinning disk with a series of holes

spiraling toward the center, for rasterization. The holes were spaced atequal angular intervals such that in a single rotation the diskwould allow light to pass through each hole and onto a light-sensitive selenium sensor which produced the electrical pulses. As an image

was focused on the rotating disk, each hole captured a horizontal "slice" of the

whole image.

Nipkow's design would not be practical until advances in amplifier tube technology became available. The device was only useful fortransmitting still "halftone" images—represented by equallyspaced dots of varying size—over telegraph or telephone lines.

Later designs would use a rotating mirror-drum scanner to capture theimage and a cathode ray tube (CRT) as a display device, but moving

images were still not possible, due to the poor sensitivity of the selenium sensors. In 1907 Russian scientist Boris Rosing became the firstinventor to use a CRT in the receiver of an experimental television system. He

used mirror-drum scanning to transmit simple geometric shapes to the CRT.

8 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 9/34

  Vladimir Zworykin demonstrates electronic television (1929).

Using a Nipkow disk, Scottish inventor John Logie Baird succeededin demonstrating the transmission of moving silhouette images in London in

1925, and of moving, monochromatic images in 1926. Baird's

scanning disk produced an image of 30 lines resolution, just enough todiscern a human face, from a double spiral of lenses. This demonstration by

Baird is generally agreed to be the world's first true demonstration of television,

albeit a mechanical form of television no longer in use. Remarkably, in1927 Baird also invented the world's first video recording system,"Phonovision": by modulating the output signal of his TV camera down to the audio range, he was able to capture the signal on a 10-inch wax audio

disc using conventional audio recording technology. A handful of Baird's

'Phonovision' recordings survive and these were finally decoded and rendered into

viewable images in the 1990s using modern digital signal-processing technology.In 1926, Hungarian engineer Kálmán Tihanyi designed a televisionsystem utilizing fully electronic scanning and display elements, and employing

the principle of "charge storage" within the scanning (or "camera") tube.

9 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 10/34

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

Also in 1927, Herbert E. Ives of Bell Labs transmitted moving

images from a 50-aperture disk producing 16 frames per minute over a cablefrom Washington, DC to New York City, and via radio from Whippany,New Jersey.[citation needed] Ives used viewing screens as large as 24 by

30 inches (60 by 75 cm). His subjects included Secretary of Commerce Herbert Hoover.[citation needed]

Philo Farnsworth

In 1927, Philo Farnsworth made the world's first working television

system withelectronic scanning of both the pickup and display devices, which

he first demonstrated to the press on 1 September 1928.

WRGB claims to be the world's oldest television station, tracing itsroots to an experimental station founded on January 13, 1928,broadcasting from the General Electric factory in Schenectady, NY,

under the call letters W2XB. It was popularly known as "WGY Television" after its

sister radio station. Later in 1928, General Electric started a second

10 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 11/34

facility, this one in New York City, which had the call lettersW2XBS, and which today is known as WNBC. The two stations were

experimental in nature and had no regular programming, as receivers were

operated by engineers within the company. The image of a Felix

the Cat doll, rotating on a turntable, was broadcast for 2 hours every day for several years, as new technology was being tested by the engineers.

In 1936 the Olympic Games in Berlin were carried by cable totelevision stations in Berlin and Leipzig where the public could view the

games live.

In 1935 the German firm of Fernseh A.G. and the United Statesfirm Farnsworth  Television owned by Philo Farnsworth signed anagreement to exchange their television patents and technology to speed

development of television transmitters and stations in their respective countries.

On 2 November 1936 the BBC began transmitting the world's firstpublic regular high-definition service from the Victorian AlexandraPalace in north London. It therefore claims to be the birthplace of television

 broadcasting as we know it today.

In 1936, Kálmán Tihanyi described the principle of plasma display,the first flat panel display system.

Mexican inventor Guillermo González Camarena also played animportant role in early television. His experiments with television (known as

telectroescopía at first) began in 1931 and led to a patent for the "trichromatic field

sequential system" color television in 1940, as well as the remote control.

Although television became more familiar in the United States with the general

 public at the 1939 World's Fair, the outbreak of World War II prevented it

from being manufactured on a large scale until after the end of the war. True

regular commercial television network programming did not begin in the U.S.

until 1948. During that year, legendary conductor Arturo Toscanini made his first of ten TV appearances conducting the NBCSymphony Orchestra, and Texaco Star Theater, starring comedian

Milton Berle, became television's first gigantic hit show.

 Amateur television (ham TV or ATV) was developed for non-commercial  experimentation, pleasure and public service eventsby amateur radio operators. Ham TV stations were on the air in many cities

 before commercial TV stations came on the air.

11 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 12/34

GEOGRAPHICAL USAGE

Television introduction by country

1930 to 1939 1970 to 1979

1940 to 1949 1980 to 1989

1950 to 1959 1990 to 1999

1960 to 1969 No data

ELEMENTS OF A TELEVISION SYSTEM

12 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 13/34

  OT-1471 Belweder, Poland, 1957

1. power switch / volume

2. brightness

3. pitch

4. vertical synchro

5. horizontal synchro6. contrast

7. channel tuning

8. channel switch

The elements of a simple broadcast television system are:

• An image source. This is the electrical signal representingthe visual image, and may be from a professional video camera in the case of live television, a video tape recorder for playback 

of recorded images, or telecine with a flying spot scanner forthe transfer of motion pictures to video).

• A sound source. This is an electrical signal from amicrophone or from the audio output of a video tape recorder.

• A transmitter, which generates radio signals (radio waves)and encodes them with picture and sound information.

13 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 14/34

• A television antenna coupled to the output of the transmitter for broadcasting the encoded signals.

• A television antenna to receive the broadcast signals.

• A receiver (also called a tuner), which decodes the picture

and sound information from the broadcast signals, and whoseinput is coupled to the antenna of the television set.

• A display device, which turns the electrical signals into visual images.

• An audio amplifier and loudspeaker, which turns electricalsignals into sound waves (speech, music, and other sounds) to accompany

the images.

Practical television systems include equipment for selecting different image

sources, mixing images from several sources at once, insertion of pre-recorded

video signals, synchronizing signals from many sources, and direct imagegeneration by computer for such purposes as stationidentification. The facility for housing such equipment, as well asproviding space for stages, sets, offices, etc., is called a televisionstudio, and may be located many miles from the transmitter.Communication from the studio to the transmitter is accomplishedvia a dedicated cable or radio system.

 Television signals were originally transmitted exclusively via land-

based transmitters. The quality of reception varied greatly,

dependent in large part on the location and type of receivingantenna. This led to the proliferation of large rooftop antennas to

improve reception in the 1960s, replacing set-top dipole or "rabbit

ears" antennas, which however remained popular. Antenna rotors,

set-top controlled servo motors to which the mast of the antenna

is mounted, to enable rotating the antenna such that it points to

the desired transmitter, would also become popular.

In most cities today, cable television providers deliver signals over

coaxial or fiber-optic cables for a fee. Signals can also bedelivered by radio from satellites in geosynchronous orbit and

received by parabolic dish antennas, which are comparatively

large for analog signals, but much smaller for digital. Like cable

providers, satellite television providers also require a fee, often

less than cable systems. The affordability and convenience of 

14 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 15/34

digital satellite reception has led to the proliferation of small dish

antennas outside many houses and apartments.

Digital systems may be inserted anywhere in the chain to provide

better image transmission quality, reduction in transmissionbandwidth, special effects, or security of transmission from

reception by non-subscribers. A home today might have the

choice of receiving analog or HDTV over the air, analog or digital

cable with HDTV from a cable television company over coaxial

cable, or even from the phone company over fiber optic lines. On

the road, television can be received by pocket sized televisions,

recorded on tape or digital media players, or played back on

wireless phones (mobile or "cell" phones) over a high-speed or

"broadband" internet connection.

DISPLAY TECHNOLOGY 

 

Digital video equipment in an edit

suite

15 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 16/34

Thanks to the advances in display technology, there are now several kinds of video

displays used in modern TV sets:

• CRT (cathode-ray tube): The most common screenswere direct-view CRTs for up to roughly 100 cm (40 inch) (in

4:3 ratio) and 115 cm (45 inch) (in 16:9 ratio) diagonals.These are the least expensive, and are a refined technology that can still

 provide the best overall picture quality value. As they do not have a fixed

native resolution, they are capable of displaying sources withdifferent resolutions at the best possible image quality. Theframe rate or refresh rate of a typical NTSC format CRT TV is29.97 Hz, and for the PAL format, 25 Hz, both are scannedwith two fields per frame in an interlaced fashion. A typicalNTSC broadcast signal's visible portion has an equivalent

resolution of about 640x480 pixels. It actually could beslightly higher than that, but the vertical blanking interval (VBI), allows other signals to be carried along with the broadcast.

• Rear Projection (RPTV): Most very large screen TVs (upto 254 cm (100 inch) and beyond) use projection technology.

 Three types of projection systems are used in projection TVs:CRT-based, LCD-based, and DLP (reflective micromirror chip)-based, D-ILA and LCOS-based. Projection television hasbeen commercially available since the 1970s, but at that time

could not match the image sharpness of the CRT; current models are vastlyimproved, and offer a cost-effective large-screen display.

o A variation is a video projector, using similar technology, which

 projects onto a screen. This is often referred to as "front projection".

•  Flat panel display (LCD or plasma): Modernadvances have brought flat panels to TV that use active matrix LCD or plasma display technology. Flat panel LCDs andplasma displays are as little as 25.4 mm (1 inch) thick and

can be hung on a wall like a picture or put over a pedestal.Some models can also be used as computer monitors.

LED technology has become one of the choices for outdoor video and

stadium uses, since the advent of bright LEDs and driver circuits.LEDs enable scalable ultra-large flat panel video displaysthat other technologies are currently not able to match in performance.

16 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 17/34

Each has its pros and cons. Flat panel LCD and plasma displays have a wide

viewing angle (around 178 degrees) so they may best suited for a home theatre

with a wide seating arrangement. Rear projection screens do not perform well indaylight or well-lit rooms and so are only suited to darker viewing areas.

HOW TELEVISION WORKS

HOW CRT TELEVISION WORKS

A cathode-ray tube (CRT) television displays an image by scanning a beam

of electrons across the screen in a pattern of horizontal lines known as a

raster. At the end of each line the beam returns to the start of the next line; at the

end of the last line it returns to the top of the screen. As it passes each point the

intensity of the beam is varied, varying the luminance of that point. A color

television system is identical except that an additional signal known as

chrominance controls the color of the spot.

Raster scanning is shown in a slightly simplified form below.

17 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 18/34

When analog television was developed, no affordable technology for storing any

video signals existed; the luminance signal has to be generated and transmitted at

the same time at which it is displayed on the CRT. It is therefore essential to

keep the raster scanning in the camera (or other device for

producing the signal) in exact synchronization with the scanning in thetelevision.

The physics of the CRT require that a finite time interval is allowed for the spot to

move back to the start of the next line (horizontal retrace) or the start of the screen

(vertical retrace). The timing of the luminance signal must allow for this.

The human eye has a characteristic called Persistence of vision. Quickly

displaying successive scan images will allow the apparent illusion  of smooth

motion. Flickering of the image can be partially solved using a long persistence 

phosphor coating on the CRT, so that successive images fade slowly. However,

slow phosphor has the negative side-effect of causing image smearing and blurring

when there is a large amount of rapid on-screen motion occurring.

The maximum frame rate depends on the bandwidth of the electronics and

the transmission system, and the number of horizontal scan lines in the image. A

frame rate of 25 or 30 hertz is a satisfactory compromise, while the

process of interlacing two video fields of the picture per frame is

used to build the image. This process doubles the apparent number of video fields

 per second and further reduces flicker and other defects in transmission.

Close up image of analog color screen

18 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 19/34

Plasma screens and LCD screens have been used in analog television

sets. These types of display screens use lower voltages than older CRT displays.

Many dual system television receivers, equipped to receive both analog

transmissions and digital transmissions have analog tuner

(television) receiving capability and must use a television antenna.

HOW PLASMA TELEVISION WORKS

 The xenon and neon gas in a plasma television is contained in

hundreds of thousands of tiny cells positioned between two plates

of glass. Long electrodes are also sandwiched between the glass

plates, on both sides of the cells. The address electrodes sit

behind the cells, along the rear glass plate. The transparentdisplay electrodes, which are surrounded by an insulating

dielectric material and covered by a magnesium oxide protective

layer, are mounted above the cell, along the front glass plate.

Both sets of electrodes extend across the entire screen. The display electrodes are

arranged in horizontal rows along the screen and the address electrodes are

arranged in vertical columns. As you can see in the diagram below, the vertical and

horizontal electrodes form a basic grid.

 To ionize the gas in a particular cell, the plasma display'stelevision charges the electrodes that intersect at that cell. It

does this thousands of times in a small fraction of a second,

charging each cell in turn.

 

19 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 20/34

 

When the intersecting electrodes are charged (with a voltage difference between

them), an electric current flows through the gas in the cell. As we saw in the last

section, the current creates a rapid flow of charged particles, which stimulates the

gas atoms to release ultraviolet photons.

The released ultraviolet photons interact with phosphor material coated on the

inside wall of the cell. Phosphors are substances that give off light when they

are exposed to other light. When an ultraviolet photon hits a phosphor atom in the

cell, one of the phosphor's electrons jumps to a higher energy level and the atom

heats up. When the electron falls back to its normal level, it releases energy inthe form of a visible light photon.

The phosphors in a plasma display give off colored light when they are excited.

Every pixel is made up of three separate subpixel cells, each with different colored

 phosphors. One subpixel has a red light phosphor, one subpixel has a green light

 phosphor and one subpixel has a blue light phosphor. These colors blend together 

to create the overall color of the pixel.

By varying the pulses of current flowing through the different cells, the control

system can increase or decrease the intensity of each subpixel color to create

hundreds of different combinations of red, green and blue. In this way, the controlsystem can produce colors across the entire spectrum.

The main advantage of plasma display technology is that you canproduce a very wide screen using extremely thin materials. And because

each pixel is lit individually, the image is very bright and looks good from almost

every angle. The image quality isn't quite up to the standards of the best cathode

ray tube sets, but it certainly meets most people's expectations.

20 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 21/34

The biggest drawback of this technology has been the price. However, falling

 prices and advances in technology mean that the plasma display may soon edge out

the old CRT sets.

RECEVING SIGNALS FOR TELEVISION

 The television system for each country will specify a number of 

television channels within the UHF or VHF frequency ranges. A

channel actually consists of two signals: the picture information is

transmitted using amplitude modulation on one frequency, and the sound is

transmitted with frequency modulation at a frequency at a fixed offset

(typically 4.5 to 6 MHz) from the picture signal.

The channel frequencies chosen represent a compromise between allowingenough bandwidth for video (and hence satisfactory picture resolution), and

allowing enough channels to be packed into the available frequency band. In

 practice a technique called vestigial sideband is used to reduce the channel

spacing, which would be at least twice the video bandwidth if pure AM was used.

Signal reception is invariably done via a superheterodyne receiver: the

first stage is a tuner which selects a television channel and

frequency-shifts it to a fixed intermediate frequency (IF). The

signal amplifier (from the microvolt range to fractions of a volt)performs amplification to the IF stages.

EXTRACTING THE SOUND

At this point the IF signal consists of a video carrier wave at one frequency

and the sound carrier at a fixed offset. A demodulator recovers

the video signal and sound as an FM signal at the offset frequency (this is

known as intercarrier sound ).

The FM sound carrier is then demodulated, amplified, and used to drive a

loudspeaker. Until the advent of the NICAM and MTS systems, TV sound

transmissions were invariably monophonic.

 STRUCTURE OF A VIDEO SIGNAL

21 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 22/34

The video carrier is demodulated to give a composite video signal; this

contains luminance, chrominance and synchronization signals;[5] this is identical to

the video signal format used by analog video devices such as VCRs or

CCTV cameras. Note that the RF signal modulation is inverted

compared to the conventional AM: the minimum video signal level corresponds to

maximum carrier amplitude, and vice versa. The carrier is never shut off 

altogether; this is to ensure that intercarrier sound demodulation can still occur.

Each line of the displayed image is transmitted using a signal as shown above. The

same basic format (with minor differences mainly related to timing and the

encoding of color) is used for PAL, NTSC and SECAM television systems.

A monochrome signal is identical to a color one, with the exception

that the elements shown in color in the diagram (the color burst, and the

chrominance signal) are not present.

22 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 23/34

Portion of a PAL videosignal. From left to right: end of a video scan line, front

 porch, horizontal sync pulse, back porch with color burst, and

beginning of next line

The front porch is a brief (about 1.5 microsecond) period inserted

between the end of each transmitted line of picture and the

leading edge of the next line sync pulse. Its purpose was to allow

voltage levels to stabilise in older televisions, preventing

interference between picture lines. The front porch is the first

component of the horizontal blanking interval which also contains

the horizontal sync pulse and the back porch.The back porch is the portion of each scan line between the end (rising edge) of the

horizontal sync pulse and the start of active video. It is used to restore the black 

level (300 mV.) reference in analog video. In signal processing terms, it

compensates for the fall time and settling time following the sync pulse.

In color TV systems such as PAL and NTSC, this period also includes the

colorburst signal. In the SECAM system it contains the reference subcarrier 

for each consecutive color difference signal in order to set the zero-color reference.

In some professional systems, particularly satellite links  between locations, the

audio is embedded within the back porch of the video signal, to save the cost of 

renting a second channel.

MONOCHROME VIDEO SIGNAL EXTRACTION

23 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 24/34

The luminance component of a composite video signal varies between 0 V and

approximately 0.7 V above the 'black' level. In the NTSC system, there is a

blanking signal level used during the front porch and back porch, and a black signal

level 75 mV above it; in PAL and SECAM these are identical.

In a monochrome receiver the luminance signal is amplified to drive the control

grid in the electron gun of the CRT. This changes the intensity of the electron

 beam and therefore the brightness of the spot being scanned. Brightness and

contrast controls determine the DC shift and amplification, respectively.

COLOR VIDEO SIGNAL EXTRACTION

Color bar generator test signal

A color signal conveys picture information for each of the red,

green, and blue components of an image (see the article on Color

space for more information). However, these are not simply

transmitted as three separate signals, because:

such a signal would not be compatible with monochrome

receivers (an important consideration when color broadcastingwas first introduced)

it would occupy three times the bandwidth of existing television,

requiring a decrease in the number of TV channels available

24 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 25/34

typical problems with signal transmission (such as differing

received signal levels between different colors) would produce

unpleasant side effects.

Instead, the RGB signals are converted into YUV form, where the Ysignal represents the overall brightness, and can be transmitted

as the luminance signal. This ensures a monochrome receiver will

display a correct picture. The U and V signals are the difference

between the Y signal and the B and R signals respectively. The U

signal then represents how "blue" the color is, and the V signal

how "red" it is. The advantage of this scheme is that the U and V

signals are zero when the picture has no color content. Since the

human eye is more sensitive to errors in luminance than in color,

the U and V signals can be transmitted in a relatively lossy 

(specifically: bandwidth-limited) way with acceptable results. The

G signal is not transmitted in the YUV system, but rather it is

recovered electronically at the receiving end.

 

Color signals mixed with video signal

In the NTSC and PAL color systems, U and V are transmitted byadding a color subcarrier to the composite video signal, and using

quadrature amplitude modulation on it. For NTSC, the subcarrier

is usually at about 3.58 MHz, but for the PAL system it is at about

4.43 MHz. These frequencies are within the luminance signal

band, but their exact frequencies were chosen such that they are

25 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 26/34

midway between two harmonics of the horizontal line repetition

rate, thus ensuring that the majority of the power of the

luminance signal does not overlap with the power of the

chrominance signal.

In the British PAL (D) system, the actual chrominance center

frequency is 4.43361875 MHz, a direct multiple of the scan rate

frequency. This frequency was chosen to minimize the

chrominance beat interference pattern that would be visible in

areas of high color saturation in the transmitted picture.

 The two signals (U and V) modulate both the amplitude and phase 

of the color carrier, so to demodulate them it is necessary to have

a reference signal against which to compare it. For this reason, ashort burst of reference signal known as the color burst is

transmitted during the back porch (re-trace period) of each scan

line. A reference oscillator in the receiver locks onto this signal

(see phase-locked loop) to achieve a phase reference, and uses

its amplitude to set an AGC system to achieve an amplitude

reference.

 The U and V signals are then demodulated by band-pass filtering

to retrieve the color subcarrier, mixing it with the in-phase and

quadrature signals from the reference oscillator, and low-pass

filtering the results.

 

 Test card showing "Hanover Bars" (color banding phase effect) in

Pal S (simple) signal mode of transmission.

26 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 27/34

NTSC uses this process unmodified. Unfortunately, this often

results in poor color reproduction due to phase errors in the

received signal. The PAL D (delay) system corrects this by

reversing the phase of the signal on each successive line, and the

averaging the results over pairs of lines. This process is achievedby the use of a 1H (where H = horizontal scan frequency) duration

delay line. (A typical circuit used with this device converts the low

frequency color signal to ultrasonic sound and back again). Phase

shift errors between successive lines are therefore cancelled out

and the wanted signal amplitude is increased when the two in-

phase (coincident) signals are re-combined.

In the SECAM television system, U and V are transmitted on

alternate lines, using simple frequency modulation of two

different color subcarriers.

In analog color CRT displays, the brightness control signal

(luminance) is fed to the cathode connections of the electron

guns, and the color difference signals (chrominance signals) are

fed to the control grids connections. This simple matrix mixing

technique was replaced in later solid state designs of signal

processing.

SYNCHRONIZATION

Synchronizing pulses added to the video signal at the end of every scan line 

and video frame ensure that the sweep oscillators in the receiver remain locked in

step with the transmitted signal, so that the image can be reconstructed on the

receiver screen.

A sync separator circuit detects the sync voltage levels and sorts the pulses into

horizontal and vertical sync. (see section below - Other technical information, for 

extra detail.)

 HORIZONTAL SYNCHRONIZATION

27 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 28/34

The horizontal synchronization pulse (horizontal sync  HSYNC ), separates the scan

lines. The horizontal sync signal is a single short pulse which indicates the start of 

every line. The rest of the scan line follows, with the signal ranging

from 0.3 V (black) to 1 V (white), until the next horizontal or vertical

synchronization pulse.

The format of the horizontal sync pulse varies. In the 525-line NTSC system it

is a 4.85 µs-long pulse at 0 V. In the 625-line PAL system the pulse is 4.7 µs

synchronization pulse at 0 V . This is lower than the amplitude of any video signal

(blacker than black ) so it can be detected by the level-sensitive "sync stripper"

circuit of the receiver .

VERTICAL SYNCHRONIZATION

Vertical synchronization (Also vertical sync or VSYNC)

separates the video fields. In PAL and NTSC, the vertical

sync pulse occurs within the vertical blanking interval. The

vertical sync pulses are made by prolonging the length of 

HSYNC pulses through almost the entire length of the scanline.

 The vertical sync signal is a series of much longer pulses,

indicating the start of a new field. The sync pulses occupy the

whole of line interval of a number of lines at the beginning and

end of a scan; no picture information is transmitted during vertical

retrace. The pulse sequence is designed to allow horizontal sync

to continue during vertical retrace; it also indicates whether eachfield represents even or odd lines in interlaced systems

(depending on whether it begins at the start of a horizontal line,

or mid-way through).

 The format of such a signal in 525-line NTSC is:

28 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 29/34

pre-equalizing pulses (6 to start scanning odd lines, 5 to start

scanning even lines)

long-sync pulses (5 pulses)

post-equalizing pulses (5 to start scanning odd lines, 4 to startscanning even lines)

Each pre- or post- equalizing pulse consists in half a scan line of 

black signal: 2 µs at 0 V, followed by 30 µs at 0.3 V.

Each long sync pulse consists in an equalizing pulse with timings

inverted: 30 µs at 0 V, followed by 2 µs at 0.3 V.

In video production and computer graphics, changes to the imageare often kept in step with the vertical synchronization pulse to

avoid visible discontinuity of the image. Since the frame buffer of 

a computer graphics display imitates the dynamics of a cathode-

ray display, if it is updated with a new image while the image is

being transmitted to the display, the display shows a mishmash of 

both frames, producing a page tearing artifact partway down the

image.

Vertical synchronization eliminates this by timing frame buffer fillsto coincide with the vertical blanking interval, thus ensuring that

only whole frames are seen on-screen. Software such as video

games and computer aided design (CAD) packages often allow

vertical synchronization as an option, because it delays the image

update until the vertical blanking interval. This produces a small

penalty in latency, because the program has to wait until the

video controller has finished transmitting the image to the display

before continuing. Triple buffering reduces this latencysignificantly.

 Two timing intervals are defined - the front porch between the end

of displayed video and the start of the sync pulse, and the back 

 porch after the sync pulse and before displayed video. These and

the sync pulse itself are called the horizontal blanking (or retrace)

29 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 30/34

interval and represent the time that the electron beam in the CRT

is returning to the start of the next display line.

VERTICAL HOLD AND VERTICAL HOLD

 The lack of precision timing components available in early

television receivers meant that the timebase circuits occasionally

needed manual adjustment. The adjustment took the form of 

horizontal hold and vertical hold controls, usually on the rear of 

the television set. Loss of horizontal synchronization usually

resulted in an unwatchable picture; loss of vertical

synchronization would produce an image rolling up or down the

screen.

CONCLUSION Television is now a important thing in our daily life. It plays a great

role in our daily life. Today we use it in various purpose . As

technology is developing day by day, television technology is also

developing day by day. New kinds of television is coming day byday. In future it will be more advanced and more powerfull.

30 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 31/34

BIBILOGRAPHY 1. www.wikipedia.com

2. www.howstuffworks.com

3. Television Frequency Table, CSGNetwork.com., a Division of ComputerSupport Group.

4. "History of the Cathode Ray Tube". About.com. Retrieved 4 October 2009.

5. "World Analogue Television Standards and Waveforms – section – Timeline".Histrorical television data 2011. Retrieved 29 January 2011.

6. R. W. Burns, John Logie Baird: television pioneer , IET, 2000 ISBN0852967977 pp. 73, 88 Mr ali283280 says: (8 October 2009). "World's First TVRecordings". Tvdawn.com. Retrieved 18 June 2010.

7. "Hungary – Kálmán Tihanyi's 1926 Patent Application 'Radioskop'". Memory of the World. United Nations Educational, Scientific and Cultural Organization(UNESCO). Retrieved 22 February 2008.

8. United States Patent Office, Patent No. 2,133,123, Oct. 11, 1938.

9. United States Patent Office, Patent No. 2,158,259, May 16, 1939

10. "Vladimir Kosma Zworykin, 1889–1982". Bairdtelevision.com. Retrieved 17April 2009.

11. Glinsky, Albert. Theremin: ether music and espionage. University of IllinoisPress, 2000. pg. 46.

12. "Philo Taylor Farnsworth (1906–71)", The Virtual Museum of the City of SanFrancisco

13. Farnsworth, Elma G., Distant Vision: Romance and Discovery on an InvisibleFrontier , Salt Lake City, PemberlyKent, 1989, p. 108.

14. "The First Television Show" Popular Mechanics, August 1930, pp. 177-179

31 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 32/34

15. "TV History". Gadgetrepublic. 1 May 2009. Retrieved 1 May 2009.

16. "Exchange of Patients Speed Home Television" Popular Mechanics, July1935 pp.24-25

17. http://www.teletronic.co.uk/tvera.htm Teletronic – The Television HistorySite

18. http://ewh.ieee.org/r2/johnstown/downloads/20090217_IEEE_JST_Trivia_Answers.pdf 

19. http://www.scitech.mtesz.hu/52tihanyi/flat-panel_tv_en.pdf 

20. http://www.google.com/patents?id=sQBkAAAAEBAJ&dq=2296019 Patent2296019 Chromoscopic Adapter for Television Adapter. Google patents

21. Kowalewski, Anthony, "An Amateur's Television Transmitter", Radio News,April 1938. Early Television Museum and Foundation Website. Retrieved 19 July2009.

22. Global TV 2010 – Markets, Trends Facts & Figures (2008–2013) International Television Expert Group

23. Global TV Revenues (2008–09) International Television Expert Group

24. iDate's Global TV Revenue Market Shares International Television ExpertGroup

25. OFCOM's Global TV Market Report 2009 International Television ExpertGroup

26. Karen Hornick "That Was the Year That Was" American Heritage, Oct. 2006.

27. Jon Stewart of " The Daily Show" was mock-outraged at this, saying, "That'swhat we do!", and calling it a new form of television, "infoganda".

28. "Kenneth Roy Thomson". Press Gazette. 7 July 2006. Retrieved 24 April2010.

29. "BCI :: Introduction to the BCI". Bci.ie. 1 October 2009. Retrieved 18 June2010.

30."viewing statistics in UK". Barb.co.uk. Retrieved 17 April 2009.

31. "The Communications Market: Digital Progress Report – Digital TV, Q32007" (PDF). Archived from the original on June 25, 2008. Retrieved 18 June2010.

32.Martin, Andrew (2011-12-27). "Plummeting TV Prices Squeeze Makers andSellers". The New York Times: pp. B1. Retrieved December 27, 2011.

33. "LCD TV Shipments Rebound Ahead of 2011 Holiday Selling Period".Retrieved in November 21, 2011.

34. New BBC iPlayer: Integration with Facebook and Twitter

35."The Rise of the Machines: A Review of Energy Using Products in the Homefrom the 1970s to Today" (PDF). Energy Saving Trust. July 3, 2006. Retrieved 31August 2007.

 

32 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 33/34

APPENDIX

CRT (cathode-ray tube)

………………………………………………….14FLAT PANEL DISPLAY 

……………………………………………………..14

GEOGRAPHICAL

USAGE………………………………………………….10

HORIZONTALSYNCHRONIZATION…………………………………..25

REAR PROJECTION (RPTV)

……………………………………………….14

RECEVING SIGNALS FOR

TELEVISION……………………………….19

SYNCHRONIZATION

………………………………………………………..25

VERTICAL SYNCHRONIZATION….

…………………………………….. 26

VERTICAL HOLD AND VERTICAL HOLD….

………………………….27

33 | P a g e

7/31/2019 Term Paper on Television by Tahsin & Parvez_ICT_3rd Batch_1st Semester_2011

http://slidepdf.com/reader/full/term-paper-on-television-by-tahsin-parvezict3rd-batch1st-semester2011 34/34