2. Television and Video Display Units
Chapter 23
Television and Video Display Units

3. Objectives
Explain the steps in the transmission of a television signal.
Discuss the scanning process.
Identify circuits in both black-and-white and color television receivers and explain their functions.
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4. Objectives Identify the size and makeup of a television channel.
Discuss a variety of television innovations, including video cassette recorders, remote control, and satellite television.
List the benefits of HDTV, as compared to analog television.
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5. Objectives
Explain the difference between multicasting and datacasting.
Discuss the compression technique of MPEG2.
Discuss the various flat-panel technologies.
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6. Television Signals Television cameras Scanning Composite video signals
Basic CRT controls
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7. Television Cameras Picture elements
Camera “sees” a scene as a combination of picture elements
Photoelectric cells in the camera respond to scene by producing a voltage
Voltages are amplified for AM carrier wave
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8. Image Orthicons
Varying degrees of light cause electrons to be emitted on the target side of the cathode and form an electronic image
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9. Scanning
Electron beam responds to point-to-point brilliance of a picture
Interlace system used in United States has 525 scanning lines
Scans odd numbered lines of pattern first, and then scans even numbered lines
Fields
Frames
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10. Scanning (Cont.) FCC sets frame frequency 30 frames per second
Horizontal deflection oscillator
Vertical deflection oscillator
The beam scans as it moves left to right
Beam must return to top to scan again after reaching the bottom
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11. Scanning (Cont.) Deflection yoke Synchronization (sync) pulse
Horizontal hold
Vertical hold
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12. Composite Video Signals
All video signals are formed the same way
FCC sets standards
Contain picture and sound information
Video is AM signal
Audio is FM signal
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13. Composite Video Signals (Cont.)
First 75% of amplitude transmits video information
Remaining 25% is for sync pulses
Higher amplitudes of video information produce darker areas in the picture
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14. Composite Video Signals (Cont.)
Screen is driven back to the pedestal, or blanking level
Sync pulse is sent in infrablack region for oscillator synchronization
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15. Basic CRT Controls CRT is used to produce images in television sets
Bias controlling current is brightness control
Raster can be seen when TV is on a vacant channel
(RCA)
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16. Review How does a television camera transmit video to television?
The photoelectric cells in a camera produce voltages. The voltages are amplified and used for modulation of the AM carrier wave, which is then transmitted to the home receiver
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17. Review What is scanning? The point-to-point examination of a picture
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18. Review
How many scanning lines are used in the scanning system of the United States?
525
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19. Review
What is a raster?
The lines on a TV screen when a vacant channel is showing
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20. Television Receivers Black-and-white television receivers
Color television receivers
Television channels
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21. Black-and-White Television Receivers
RF amplifier stage
Similar to function in superheterodyne radio
Provides constant gain and selectivity
Video signal amplified and fed to mixer
Mixer stage
Intermediate frequency is produced
Fine-tuning
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22. Black-and-White Television Receivers (Cont.)
Tuner, or front end
Put together in the factory
No adjustments should be made on these without thorough understanding
PIX-IF amplifiers
Amplify broad band of frequencies
Voltage gain is reduced
Intercarrier system
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23. Black-and-White Television Receivers (Cont.)
Video detector, or demodulator, stage
Same detection process as radio
Video signal is separated and fed to next stage
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24. Black-and-White Television Receivers (Cont.)
Video amplifiers
Sound IF amplifiers
FM audio detectors
AF amplifiers
Sync separators
Sync amplifiers
Horizontal AFCs
Horizontal oscillators
Horizontal outputs
Horizontal output transformers (HOTs)
High voltage rectifiers
Dampers
Vertical oscillators
Vertical outputs
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25. Special-Purpose Circuits
DC restoration
Average value of video signal taken from detector
Used to set bias on the CRT
AGC
Provides fairly constant output from detector
Varies gain of amplifiers
Rectifies video signal to produce negative voltage
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26. Color Television Receivers
Developed in late 1940s by RCA Laboratories
Shadow mask picture tubes
(Sylvania-GTE)
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27. Color Television Receivers (Cont.)
Three colors used in color television
Any color can be produced on the screen by combining red, blue, and green
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28. Color Television Receivers (Cont.)
Delta-type tubes
Three electron guns in neck assembly of picture tube
Shadow mask or aperture ensures the electron beams strike the dots correctly
(Sylvania-GTE)
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29. Color Television Receivers (Cont.)
Color line is made by mixing the electron beams
In-line gun assemblies
Color television can produce both color and black-and-white pictures
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30. Television Channels
FCC assigns portions of radio frequency spectrum for television channels
Very high frequency (VHF)
Ultra high frequency (UHF)
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31. Television Channels (Cont.)
Frequencies of at least 4 MHz are needed to send a clear, sharp picture
Upper sideband in commercial TV is transmitted without attenuation
Vestigial-sideband filter partly removes lower sideband at transmitter
Sound is transmitted as frequency-modulated signal at center frequency
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32. Review
What changes the frequency of the oscillator slightly to provide the best response?
Fine-tuning
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33. Review What is the voltage amplifier stage that increases sync pulses?
Sync amplifier
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34. Review
What are two special purpose circuits that have been used to improve the basic television circuit?
DC restoration and automatic gain control (AGC)
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35. Review What invention made color television possible?
Shadow mask picture tube
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36. Television Innovations
Video cassette recorders (VCRs)
Digital video recorder (DVRs)
Remote controls
Large-screen projection TVs
Satellite TVs
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37. VCRs Can record and play back videotapes Most have four video heads
Magnetic tape with iron oxide
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38. VCRs (Cont.) Can record Voice Video Speed information
End of tape location
Copyright
Anticopy coding
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39. DVRs Combine computer and television components
Form a television receiver
Receive television signal and can record the program
Hard disk drive used for recording medium
Capable of recording and storage
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40. Remote Controls Application of infrared light and digital techniques
Digital code sent out of remote control
Infrared sensor on TV amplifies and decodes signal
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41. Large-Screen Projection TVs
Use special electron gun assemblies to project three separate images onto a screen
Loss of clarity of video image
525 lines per frame become distracting
No real magnification
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42. Satellite TVs Geostationary orbit
First communications satellite was launched in 1962
Amplifier increases strength of communication signal for its broadcast back to earth
Carries both standard traveling wave tubes and solid-state power amplifiers
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43. Communication Satellites
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44. Satellite Signals
Signals made by communication stations on earth are beamed up to satellites
Amplified by satellite and then sent back to earth
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45. Satellite Transmission
Focal point
Feedhorn
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46. Coaxial Cable Designed to carry high frequency signals
Limits radio waves generated from center core conductor to the area between the core conductor and the shield
The shield absorbs radio signal emanating from core conductor as high frequency passes through
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47. FAKRA SMB Connectors Very small connectors
Designed for small diameter coaxial cable or micro-coaxial cable
Used for automotive satellite radio and antenna connections
Smallest connector used at this time
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48. Review
What part of a VCR reads information from the recorded tape during playback?
Video head
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49. Review What is combined to form a DVR?
A television signal and hard disk drive
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50. Review Describe the signals sent to and from a satellite.
The signal sent up from a studio is a narrow signal targeting the satellite, while the signal sent down from the satellite is a wide signal designed to cover a large area of the earth
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51. Review What part of a satellite dish acts as a receiver? A feedhorn
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52. Improvements to Analog Television
Analog television merged with digital systems used by computer monitors
Many features were added
Greater color-depth control
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53. High Definition Television (HDTV)
FCC approved of digital television standard in 1996
Allows for higher resolutions and wider display screen than analog systems
Uses digital broadcasting techniques
More information-rich data to be transmitted
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54. Broadcasting Multiple Channels
Digital broadcasting can broadcast multiple channels in same bandwidth
Multicasting
Datacasting
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55. HDTV Systems Digital camera to record images at high resolution
Digital receiver to convert received broadcasts into image and sound
Display unit capable of producing images at HDTV resolution
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56. Charged Coupled Devices (CCDs)
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57. Digital Camera Technology
CCD converts individual packets of electrical charge into series of analog signals representing level of light amplitude at each photo sensor location
Analog-to-digital converter (ADC)
Once converted, digital pattern can be stored or transmitted
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58. Three-CCD Systems
Three sets of CCD sensors used for full-color images and higher resolutions
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59. HDTV Picture Quality
National Television Standards Committee (NTSC) formed analog standards
Advanced Television Systems Committee (ATSC) developed digital standards
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60. ATSC Standards 18 scanning formats Progressive scanning Frame rate
Aspect ratio
16:9
4:3
HDTV capable of 720p and 1080i vertical lines
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61. Analog Quality vs. Digital Quality
Convert scan lines to maximum number of pixels
480 × 440 pixels for analog
1920 × 1080 pixels for HDTV
Moving Picture Experts Group developed MPEG2 standard
Sound quality improvements
Enhanced definition television (EDTV)
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62. Digital Light Projection (DLP) Television
Developed based on digital mirror device (DMD)
DMD can contain over 1.3 million mirrors
DMD combined with light source and lens to create DLP system
(Courtesy of Texas Instruments)
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63. Flat-Panel Displays
Many televisions now use flat-panel technology instead of picture tubes
Control individual pixels electrically
Vertical and horizontal conductors
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64. Gas-Plasma Displays Electro-luminescence
Consist of millions of cells between two glass plates
Controlled by varying pulses of current
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65. Liquid Crystal Display (LCD) Panels
Most common flat-panel displays
Two categories
Active
Passive
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66. How Color LCDs Work Backlight generates light Polarized light
Liquid crystal between two filters
Light passing through filters depends on amount of voltage applied
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67. Passive-Matrix Display
Grid of semitransparent conductors run to each crystal
Two major circuits
Columns
Rows
Response time is slow because current must travel along row and column until it arrives at designated pixels
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68. Active-Matrix Display
Provides better image than passive-matrix
Constant supply of voltage to each cell
Results in brighter picture
Thin film transistor liquid crystal displays (TFT-LCDs)
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69. LCD vs. CRT Displays LCDs are smaller and lighter than CRTs
LCDs require less power to run
LCDs generate less heat
LCDs create more detailed images
LCDs produce less electromagnetic interference
LCDs do not have industry-wide standard
LCDs cost more for the same size of CRT
LCDs have difficulty scaling images properly without distortion
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70. Display Resolution Higher resolution results in more detailed images
Images displayed at lower resolutions lose their sharpness
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71. Philips SXGA Triple-Input Display Controllers
Accept input from analog, digital, and parallel sources
Analog input accepts UHF and VHF frequencies
Digital input accepts HDTV broadcasts from cable and computer systems
Parallel interface accepts input from USB connections
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72. Standards Organizations
Video Electronics Standards Organization (VESA)
Digital Flat Panel (DFP)
Led by Compaq
Digital Visual Interface (DVI)
Led by Intel
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73. Home Theater Connector Types
RF and F-type
Composite video
S-video
Component video
High Definition Multimedia Interface
ToskLink
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74. RF and F-Type Connections
Support poorest quality of video images
Found on older technologies
Use standard coaxial cable
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75. Composite Video Cables
Use only one cable for video, two for stereo sound
Provide better signal than RF or F-type connections
Provide worse signal than S-video
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76. S-Video Connectors Four-pin or nine-pin connectors
Separate signals for video signal chrominance and luminance
No way to misconnect audio and video cables
Video-in and video-out (VIVO) configurations
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77. Component Video Connectors
Better quality than S-video
Found on high-performance devices
Do not carry audio signal
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78. High Definition Multimedia Interface Connectors
Supply video and audio in uncompressed all-digital signal format
Exceed HDTV standard
Colorimetry
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79. ToskLink Connectors Limited to audio
Support signals between home theater equipment
Provide connections for fiber optic cable
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80. Review What is multicasting?
Broadcasting multiple channels within the same bandwidth
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81. Review What is datacasting?
Transmitting additional information along with a video image
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82. Review
Which component does HDTV use in place of the analog television’s vacuum tube imaging?
Charged coupled device (CCD)
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83. Review
What committee’s standards have been designed to replace the original television and video standards in the United States?
Advanced Television Systems Committee (ATSC)
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84. Review What is the purpose of the MPEG2 standard?
To increase the amount of video data transmitted in an HDTV system
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85. Review
Which flat-panel display system operates on the principle of electro-luminescence?
Gas-plasma displays
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86. For Discussion Discuss the controls found in a television receiver.
Discuss various types of video display.
Discuss the transition from analog to digital television.
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87. Glossary Active-matrix
A display in which each individual cell in the grid has its own individual transistor.
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88. Glossary Advanced Television Systems Committee (ATSC) AF amplifier
A committee, established in 1983, that developed standards for digital television broadcasting and receivers. These standards, adopted by the FCC, have been designed to eventually replace the NTSC standards.
AF amplifier
Used to amplify audio frequencies.
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89. Glossary Aspect ratio Brightness control
The ratio of width to height of a television picture. Aspect ratio standards can be either 4:3 or 16:9.
Brightness control
Control from a TV remote that changes the bias on the control grid.
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90. Glossary Charged coupled device (CCD)
An integrated circuit consisting of an array of photo sensors that convert light from an image into electrical energy. CCDs are commonly found in scanners and digital cameras.
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91. Glossary
Damper
Stage that dampens out oscillations in the deflection yoke after retrace in a television set. Used to prevent oscillations in the horizontal output transformer.
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92. Glossary
Datacasting
A digital broadcasting technique that allows for the transmittal of additional information along with the video image. Stock prices, weather reports, sports scores, background or human interest stories about the actors in the movie being viewed, or any information found on the Internet can be incorporated into the display screen.
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93. Glossary Deflection yoke Delta-type Demodulator
Coils that surround a picture tube.
Delta-type
The first color picture tube, using three electron guns, a screen, and a shadow mask.
Demodulator
Device used to remove the video portion of a signal from a carrier wave.
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94. Glossary Electro-luminescence
The display of light created when a high frequency signal passes through a solid or liquid, resulting in the release of photons.
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95. Glossary Enhanced definition television (EDTV) Feedhorn
A system that receives digital transmissions, but displays images at 480p or higher. The fact that it can receive high definition television transmissions and decode them makes it an enhanced system.
Feedhorn
A receiver located in the focal point of a satellite dish.
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96. Glossary Field Fine-tuning One scan of 262 1/2 lines.
Slightly changes the frequency of the oscillator to provide the best response for an incoming signal.
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97. Glossary FM audio detector Focal point
Detects the frequency variations in the modulated signal and converts them to an audio signal.
Focal point
The small point in a satellite dish that receives signals.
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98. Glossary Frame Frame rate
One set of the odd- and even-numbered fields in a scanning pattern.
Frame rate
The number of times per second an image is updated on a video display screen. Currently, three frame rates exist: 60, 30, and 24 frames per second.
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99. Glossary Front end Geostationary orbit
In a television, the RF amp, mixer, and oscillator combined into one unit. Also called the tuner.
Geostationary orbit
An object in orbit above, and rotating at the same speed as, the earth.
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100. Glossary High definition television (HDTV) High voltage rectifier
Any television system capable of transmitting a picture resolution greater than 525 lines per screen.
High voltage rectifier
Rectifies the high ac voltage developed by the horizontal output transformer in a television receiver.
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101. Glossary Horizontal AFC
In a television receiver, the horizontal oscillator frequency is compared to the sync pulse frequency. If they are not the same, voltages are developed that change the horizontal oscillator to the same frequency.
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102. Glossary Horizontal hold Horizontal oscillator
In older televisions, the control that makes slight horizontal adjustments so the oscillators can lock in with the sync pulses.
Horizontal oscillator
Provides the sawtooth waveform needed for horizontal scanning in a television receiver.
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103. Glossary Horizontal output
Correctly shapes the sawtooth waveform for the horizontal deflection coils in a television receiver. Also drives the horizontal deflection coils and provides power for the high-voltage rectifier.
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104. Glossary Horizontal output transformer (HOT) In-line
Shocked by the output of the horizontal oscillator, this autotransformer develops high ac voltage in a television receiver.
In-line
Type of gun assembly that followed the shadow mask tube, having different types of apertures available.
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105. Glossary Liquid crystal display (LCD)
1. A digital or alphanumeric display unit that can be used in visual outputs. 2. A type of display that operates on the principle of polarized light passing through tiny crystals of liquid.
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106. Glossary
Mixer
Stage of television receiver during which the incoming video signal is mixed with the signal from an oscillator to produce an intermediate frequency.
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107. Glossary
MPEG2
An image compression standard, developed by the Moving Picture Experts Group, used to increase the amount of video data that can be transmitted in an HDTV system.
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108. Glossary Multicasting
A digital broadcasting technique that allows, not only for multiple channels to be broadcast, but also for two to four channels to be broadcast in the same single-channel bandwidth.
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109. Glossary National Television Standards Committee (NTSC)
A committee that formulated the standards for analog television and video in the United States. The NTSC standard calls for 525 scan lines at a 60 Hz refresh-rate, based on the interlace technique. NTSC is not compatible with most computer video systems and must be converted before it can be displayed.
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110. Glossary Passive-matrix Picture element
A type of liquid crystal display that has a grid of semitransparent conductors running to each crystal used as part of the individual pixel.
Picture element
A small area or dot of varying intensity from black to white that contains part of the visual image of a scene.
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111. Glossary Pixel PIX-IF amplifier
The smallest unit used to designate an area on a graphic display.
PIX-IF amplifier
Amplifies the output of the mixer stage.
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112. Glossary Polarized light
A filtered light consisting of light waves that are the same shape and of a single frequency, rather than the entire spectrum of light.
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113. Glossary Progressive scanning
A method of constructing an image of a display by capturing and transmitting the entire image at one time. With this method, each line is placed on the screen progressively in one sweep, rather than in two sweeps, as in interlaced scanning.
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114. Glossary Raster Resolution
Area of light produced on the screen of a television picture tube by an electron beam. Contains no picture information.
Resolution
A measurement, in pixels, of the quality of an image. The higher the resolution, the higher the quality or more detailed the image.
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115. Glossary RF amplifier Scanning Used to amplify radio frequencies.
Sweeping an electron beam across each element of a picture in successive order to reproduce the total picture in television.
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116. Glossary Shadow mask picture tube Sound IF amplifier
First type of color television, using a focus electron gun and a thin sheet of perforated material placed directly behind the viewing screen.
Sound IF amplifier
Where an FM sound signal is amplified in a television receiver.
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117. Glossary Sync amplifier Sync separator
A voltage amplifier stage that increases the sync pulses in a television receiver.
Sync separator
A circuit that removes the horizontal and vertical sync pulses transmitted as part of the composite video signal in a television receiver.
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118. Glossary Synchronization (sync) pulse
Used to trigger an oscillator or a circuit.
Thin film transistor liquid crystal display (TFT-LCD)
Most common type of display that consists of a matrix of thin film transistors spread across the entire screen.
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119. Glossary Tuner Ultra high frequency (UHF)
The RF amp, mixer, and oscillator combined in one unit.
Ultra high frequency (UHF)
Television frequencies that cover channels 14 to 83.
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120. Glossary Vertical hold Vertical oscillator
In older televisions, the control that makes slight vertical adjustments so the oscillators can lock in with the sync pulses.
Vertical oscillator
Receives the output of the sync amplifier through a vertical integration network in a television receiver.
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121. Glossary Vertical output Very high frequency (VHF)
Refers to the amplifier used by the output of the oscillator to provide the proper currents in the deflection yoke for vertical scanning in a television receiver.
Very high frequency (VHF)
Television frequencies that cover channels 2 to 13.
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122. Glossary Video amplifier Video detector Video head
Used to amplify video frequencies.
Video detector
Receives the output from the last intermediate frequency stage in a television receiver.
Video head
A tiny electromagnet in a VCR that reads information from the recorded tape during playback.
© Goodheart-Willcox Co., Inc.
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