Chapter 23 Television and Video Display Units Objectives

Chapter 23 Television and Video Display Units

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. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Objectives • Explain the difference between multicasting and datacasting. • Discuss the compression technique of MPEG 2. • Discuss the various flat-panel technologies. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Television Signals • • Television cameras Scanning Composite video signals Basic CRT controls © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Image Orthicons • Varying degrees of light cause electrons to be emitted on the target side of the cathode and form an electronic image © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Scanning (Cont. ) • Deflection yoke • Synchronization (sync) pulse • Horizontal hold • Vertical hold © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Composite Video Signals (Cont. ) • Screen is driven back to the pedestal, or blanking level • Sync pulse is sent in infrablack region for oscillator synchronization © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What is scanning? The point-to-point examination of a picture © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review How many scanning lines are used in the scanning system of the United States? 525 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What is a raster? The lines on a TV screen when a vacant channel is showing © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Television Receivers • Black-and-white television receivers • Color television receivers • Television channels © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Black-and-White Television Receivers (Cont. ) • • Video amplifiers Sound IF amplifiers FM audio detectors AF amplifiers Sync separators Sync amplifiers Horizontal AFCs Horizontal oscillators © Goodheart-Willcox Co. , Inc. • Horizontal outputs • Horizontal output transformers (HOTs) • High voltage rectifiers • Dampers • Vertical oscillators • Vertical outputs Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Color Television Receivers • Developed in late 1940 s by RCA Laboratories • Shadow mask picture tubes (Sylvania-GTE) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Color Television Receivers (Cont. ) • Three colors used in color television • Any color can be produced on the screen by combining red, blue, and green © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Television Channels • FCC assigns portions of radio frequency spectrum for television channels – Very high frequency (VHF) – Ultra high frequency (UHF) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 frequencymodulated signal at center frequency © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What changes the frequency of the oscillator slightly to provide the best response? Fine-tuning © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What is the voltage amplifier stage that increases sync pulses? Sync amplifier © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What are two special purpose circuits that have been used to improve the basic television circuit? DC restoration and automatic gain control (AGC) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What invention made color television possible? Shadow mask picture tube © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Television Innovations • • • Video cassette recorders (VCRs) Digital video recorder (DVRs) Remote controls Large-screen projection TVs Satellite TVs © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

VCRs • Can record and play back videotapes • Most have four video heads • Magnetic tape with iron oxide © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

VCRs (Cont. ) • Can record – Voice – Video – Speed information – End of tape location – Copyright – Anticopy coding © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Remote Controls • Application of infrared light and digital techniques • Digital code sent out of remote control • Infrared sensor on TV amplifies and decodes signal © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Communication Satellites © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Satellite Signals • Signals made by communication stations on earth are beamed up to satellites • Amplified by satellite and then sent back to earth © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Satellite Transmission • Focal point • Feedhorn © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What part of a VCR reads information from the recorded tape during playback? Video head © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What is combined to form a DVR? A television signal and hard disk drive © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What part of a satellite dish acts as a receiver? A feedhorn © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Improvements to Analog Television • Analog television merged with digital systems used by computer monitors • Many features were added • Greater color-depth control © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Broadcasting Multiple Channels • Digital broadcasting can broadcast multiple channels in same bandwidth • Multicasting • Datacasting © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Charged Coupled Devices (CCDs) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Three-CCD Systems • Three sets of CCD sensors used for full-color images and higher resolutions © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

HDTV Picture Quality • National Television Standards Committee (NTSC) formed analog standards • Advanced Television Systems Committee (ATSC) developed digital standards © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

ATSC Standards • • 18 scanning formats Progressive scanning Frame rate Aspect ratio – 16: 9 – 4: 3 • HDTV capable of 720 p and 1080 i vertical lines © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 MPEG 2 standard • Sound quality improvements • Enhanced definition television (EDTV) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Flat-Panel Displays • Many televisions now use flat-panel technology instead of picture tubes • Control individual pixels electrically • Vertical and horizontal conductors © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Gas-Plasma Displays • Electro-luminescence • Consist of millions of cells between two glass plates • Controlled by varying pulses of current © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Liquid Crystal Display (LCD) Panels • Most common flat-panel displays • Two categories – Active – Passive © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

How Color LCDs Work • Backlight generates light • Polarized light • Liquid crystal between two filters • Light passing through filters depends on amount of voltage applied © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. • LCDs do not have industry-wide standard • LCDs cost more for the same size of CRT • LCDs have difficulty scaling images properly without distortion Permission granted to reproduce for educational use only.

Display Resolution • Higher resolution results in more detailed images • Images displayed at lower resolutions lose their sharpness © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Standards Organizations • Video Electronics Standards Organization (VESA) • Digital Flat Panel (DFP) – Led by Compaq • Digital Visual Interface (DVI) – Led by Intel © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Home Theater Connector Types • • • RF and F-type Composite video S-video Component video High Definition Multimedia Interface Tosk. Link © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

RF and F-Type Connections • Support poorest quality of video images • Found on older technologies • Use standard coaxial cable © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Component Video Connectors • Better quality than S -video • Found on highperformance devices • Do not carry audio signal © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

High Definition Multimedia Interface Connectors • Supply video and audio in uncompressed alldigital signal format • Exceed HDTV standard • Colorimetry © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Tosk. Link Connectors • Limited to audio • Support signals between home theater equipment • Provide connections for fiber optic cable © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What is multicasting? Broadcasting multiple channels within the same bandwidth © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What is datacasting? Transmitting additional information along with a video image © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review Which component does HDTV use in place of the analog television’s vacuum tube imaging? Charged coupled device (CCD) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

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) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review What is the purpose of the MPEG 2 standard? To increase the amount of video data transmitted in an HDTV system © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Review Which flat-panel display system operates on the principle of electro-luminescence? Gas-plasma displays © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

For Discussion • Discuss the controls found in a television receiver. • Discuss various types of video display. • Discuss the transition from analog to digital television. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.