Television, also called TV, is one of our most important means of communication. It brings moving pictures and sounds from around the world into millions of homes. People with a television set can sit at home and watch the leader of a nation make a speech or visit a foreign country. They can see a war being fought, and they can watch government leaders try to bring about peace. Through television, viewers can see and learn about people, places, and things in distant lands. Television can take viewers into the depths of the ocean, out into space, and into strange worlds that can be seen only beneath a microscope. The name television comes from a Greek word meaning far and a Latin word meaning to see. Thus, television means to see far. 
Television also brings its viewers a steady stream of programs designed to entertain and inform. Entertainment programs include cartoons, comedies, dramas, game shows, motion pictures, sports events, and variety shows. Informational programs include documentaries, news, political coverage, and talk shows.
Many homes have digital video recorders (DVR’s) that enable people to record TV programs for later viewing. Video players enable people to watch shows on DVD’s or from the internet. People can use a TV set with an electronic game system to play games. New technologies have brought the abilities of a computer to television and have provided new ways to use television for information and entertainment.
Most homes in industrialized nations have at least one television set. Because of its widespread popularity, television has an important influence on today’s culture, including how people spend their time and money, and what they see and learn.
The first two sections of this article will discuss the entertainment and information offered by various forms of television and will explain how television programs are produced. The article will describe the television industry in the United States and throughout the world, trace the history of TV broadcasting in the United States, and discuss television’s effects. Later sections will explain how TV signals are created, transmitted, and received, and how television technology has developed. A final section will describe careers in television.
What television offers
Many people watch television programs that are broadcast over the air by commercial or public television stations. In many countries, people who own television sets may subscribe to cable television services, which use cables to bring programs to the home. Other households subscribe to direct-broadcast satellite (DBS) services, which enable viewers to receive signals directly from satellites. Viewers pay a fee for these services. In addition, some households watch television through video-on-demand streaming services accessible on the internet. Streaming technology enables people to listen to or view media while it is being transmitted, rather than wait for an entire file to download. Some streaming services require a subscription fee, and others are free.
Commercial television
is broadcast by stations that sell advertising time to pay for their operating costs and to make a profit. Most commercial television stations broadcast many more entertainment programs than any other kind. These shows include light dramas called situation comedies or sitcoms; action-packed dramas about detectives, doctors, and lawyers; and movies, including some made expressly for television. Entertainment programs also include game shows, soap operas (daytime dramas), and children’s shows. 
Another kind of commercial television program is the documentary. A documentary is a dramatic, but nonfictional, presentation of information. Some TV documentaries entertain as well as inform. These include travel programs about faraway places. Television also presents documentaries about such serious social issues as alcoholism, drug abuse, poverty, and racial prejudice. The newsmagazine show is a popular format for the presentation of these documentaries.
Some commercial television stations broadcast many talk shows. On these shows, a host interviews people from many walks of life, including athletes, authors, motion-picture and TV stars, politicians, and groups of people who share a common problem or experience.
Commercial television stations may also cover sports events, from baseball and football to table tennis and skiing. Every two years, TV brings its viewers the colorful Olympic Games. 
Most commercial stations broadcast brief summaries of local, national, and international news every day. These broadcasts may also cover sports events and issues of local concern.
Public television
is broadcast by stations that are nonprofit organizations. Public television usually provides more educational and cultural programming than does commercial television. Public stations broadcast programs on a wide range of subjects—from literature and physics to cooking and yoga.
Public television stations offer many programs that combine entertainment and cultural enrichment. They telecast such offerings as plays by leading dramatists, performances of ballets and symphonies, and surveys of art and history. Such television shows may draw audiences that are small by commercial TV standards, but much larger than the number that could attend a performance in a theater or concert hall. News and current affairs programs make up an important portion of programming for most public television stations.
Cable television
delivers signals to home TV sets through cables. Many cable systems carry more than 150 channels—many more than can be broadcast over the airwaves even in the largest urban areas. This increase in the number of channels available has made narrowcasting possible. Unlike broadcasting, which tries to appeal to the largest possible audience, narrowcasting offers programs that appeal to a particular age, ethnic, or interest group. For example, cable channels may specialize in movies, news, sports, music, comedy, health, religion, weather, or programs in a particular language. Such channels focus on attracting viewers with particular interests. Some communities also require cable operators to reserve channels for programs of local interest, such as city council meetings or local school graduation ceremonies.
Satellite television
enables viewers to receive signals directly from satellites. Millions of homes in many countries receive signals from direct-broadcast satellites (DBS). Satellite transmissions cover a wide reception area. A satellite over western Europe, for example, can beam programs to viewers in France, Germany, the Netherlands, the United Kingdom, and other countries. Subscribers use dish-shaped antennas to receive DBS signals. Most DBS programming is provided by the same services that supply programs to cable television.
Streaming television.
Video-on-demand streaming services are available over the internet. Such services provide libraries of video content that users may watch at any time, rather than according to a fixed schedule. Such streaming services as Netflix reach an international market. Others are accessible only within one country.
Closed-circuit television
Home entertainment systems
include digital video recorders (DVR’s), also called personal video recorders (PVR’s), and electronic game systems. Each of these devices sends video and audio signals to a viewer’s television set, usually via cables that connect the device to the TV. Many people connect home entertainment devices to a stereophonic sound system to provide sound similar to that in a movie theater.
DVR’s
enable people to record television programs and play them back later. DVR’s record and store television images and sound in digital (numerically encoded) form on a hard drive similar to that of a computer. Some DVR’s can store hundreds of hours of programs.
Most DVR’s allow the viewer to pause a television program while it is being broadcast. The device continues to record the program onto its hard drive so that the entire program can be viewed later. Most DVR’s also allow the viewer to fast-forward through commercial breaks, although such service providers as cable companies can disable this function. Additionally, most DVR’s can record more than one program at a time. Users also can set DVR’s to automatically find and record favorite shows when they are broadcast. A DVR may be built into a television set, or it may be a separate piece of equipment called a set-top box. Set-top boxes usually require a monthly subscription fee for a company’s programming service. There are also software packages that enable computers to function as a DVR.
People also may buy or rent prerecorded digital video discs (DVD’s) or Blu-ray discs to watch with stand-alone players or on computers. Many of these are recordings of movies, TV series, concerts, or sports events.
Many people like to capture vacations, parties, and family events on video. Camcorders combine a camera and a recording mechanism in one unit. Smartphones also have cameras that can record videos. Videos recorded on camcorders and smartphones can be played back on a television set.
Electronic game systems
often use a television screen to display the action of the game. A computer called a video game console can be connected to a TV set. The console reads games from cartridges, DVD’s, or programs downloaded or streamed from the internet. Players operate controls that move electronic characters and other images that appear on the TV screen. Video game consoles also can be used to stream television programs and other videos.
Producing television programs
The production of a television show is a complicated process. A program requires detailed planning, careful preparation, and the combined efforts of many people.
Most shows are produced in television studios. But TV programs are also created in movie studios, on city streets, in stadiums, and even in distant jungles. Most TV programs—including most scripted entertainment shows—are prerecorded and then telecast later.
Broadcasters telecast some programs live (as they happen). Live telecasts include newscasts, coverage of sports events, talent competitions, political conventions, and speeches by world leaders.
Planning and preparation.
The planning of TV shows begins in the programming department of the companies that broadcast them. Networks and stations produce many programs themselves. Major studios and independent producers create other programs and sell them to networks and stations. In either case, the programming department decides which programs to produce and which to purchase. It also decides when each program will be broadcast. If the programming department decides to produce a program, it assigns a producer who assumes creative and administrative control over the show.
The producer
usually begins by obtaining a script and choosing a director. Sometimes—especially for uncomplicated shows—producers write their own script. They may also serve as their own director—in which case they become a producer-director. But more often, the producer assigns the scriptwriting to a professional writer or team of writers, and the directing to a professional director. The producer and director select the talent—that is, actors and other people who will appear on the show. The producer also chooses the production specialists needed to produce the show. These people may handle lighting, photography, music, and costume design. Producers and directors of entertainment shows generally work closely together. The producer assumes overall creative leadership, while the director guides operations on the set. The producer of a news program decides which issues and events to include in the newscast and in what order to present them.
Writers
prepare the scripts for television programs. A television script is a written account of what is to be said and done during the program. 
The amount of detail a script contains varies, depending on the program. A talk show script, for example, may include only the host’s opening remarks and some of the key questions to ask the guests. During most of the show, the host and the guests carry on ad-libbed (unplanned) conversations. A script for a television drama, on the other hand, includes every word to be spoken by the cast members. It also describes the actions they are to perform and may include suggestions for scenery or other creative elements. For a newscast, writers prepare the script that the announcers read. Reporters usually prepare questions and comments for news stories they cover outside the studio.
The director.
After the writers finish the script, the director reads it and decides how to translate it into an actual television program. Directors develop opinions about how the characters should speak, move, and generally behave. They decide what camera shots will be needed to create the effects they visualize. Sometimes, the director has an artist prepare a storyboard (series of drawings) that shows how key parts of the program will look. The script and the storyboard act as a blueprint during the planning process.
Production specialists.
The producer and director call on many production specialists to help prepare the program. Craftworkers and artists work with the art director to design and build the show’s scenery. A costume designer creates or obtains costumes needed for the production. A property manager gathers special items called props. These items may include furniture, other household items, and automobiles. Specialists in technical work advise the producer and director on what kinds of cameras, microphones, and lights will be needed. A production manager, also called a production coordinator, sees to it that all the required equipment is available when needed.
Talent
is a technical term for the people who appear on television programs. Talent may appear on television as themselves, as do newscasters, sports announcers, and talk show hosts. Or the talent may play someone else, as do actors in a TV drama or situation comedy.
Selection of talent ranks among the key steps in the planning of a television program. The producer and director do this important job. If the talent are big stars, they may get television roles because of their fame and proven ability. Usually, however, the talent must audition (try out) for the parts they want to play. During an audition, the director and producer may ask the talent to take a screen test (perform in front of a camera).
The talent who earn a job get a script so they can study their lines. An actor may have less than a week to learn the lines for a one-hour drama. Those who perform on TV’s daily soap operas have only a few hours each day to memorize their lines.
Rehearsals
are practice sessions for TV shows. Most TV productions require at least one rehearsal. Complicated productions often require many more.
During a rehearsal, the talent—under the director’s guidance—practice their lines and their actions. The director also directs the actions of the camera operator and other off-camera workers.
Rehearsal for a dramatic production may begin with a script reading. Then, the director may call for a dry run (rehearsal without equipment or costumes). Finally, the director calls for a dress rehearsal, also known as a camera rehearsal, in the studio. The goal of a dress rehearsal is to achieve a performance that is the same as the final production will be. In fact, directors sometimes record both the dress rehearsal and the actual production. In reviewing both recordings, directors may decide that parts of the dress rehearsal came out better than the actual production. They may then substitute the parts of the dress rehearsal they like for the corresponding parts of the actual production.
Production.
When the time comes to shoot a program, everything needed for the process is brought together in a television studio or other location. Workers put the scenery and props in place. Other workers set up floodlights and spotlights to achieve various effects.
Some studios have rows of seats much like a theater where visitors can watch shows being produced. Many game shows and talk shows are produced in front of a studio audience.
Before the show begins, makeup artists apply makeup to the talent who will appear on the show. Makeup helps people look natural on camera. The talent put on special costumes, if the show calls for such costumes. Finally, the talent perform before the cameras.
The cameras
used for shooting the performance are mounted on wheels so the camera operators can move them around. Cameras can tilt up and down and turn left and right to follow action. In addition, cameras can adjust from a long-range view of a scene to a close-up by means of a device called a zoom lens. Zooming (moving in and out on scenes) is a widely used production technique. Some cameras are operated by remote control.
Microphones.
Many TV productions involve the use of boom microphones. This type of microphone is attached to a boom (long metal arm). A worker called the boom operator moves the microphone above and in front of the person speaking. For dramatic productions, it is essential that the microphone stay out of camera view. Sometimes, television makes use of hidden microphones concealed in or behind scenery or props or in a performer’s clothing. Tiny microphones called lavalier mikes or lapel mikes may hang around a performer’s neck or attach to clothing. Talk-show hosts may use hand microphones when moving around the audience.
Post-production
refers to the total process of putting a program together in final form. Some important steps in post-production are editing, adding music and sound effects, and adding visual effects.
Editing.
Most dramas and comedies are shot scene-by-scene with stopdowns (pauses) between scenes. Each recorded scene is called a take. If the director likes the take, the crew goes on to another one. If the director does not like it, he or she can call for a retake (shooting the scene over again). Directors often shoot scenes out of order. If, for example, the first and last scenes of a TV drama take place in the same location, the director may shoot them one right after the other. The director will also shoot other scenes in an order that is most efficient and least expensive.
After shooting is complete, editors put all the scenes together in their proper order to create a continuous story. Editors do this work on computers. In preparation for editing, the pictures and the sound must be digitized—that is, converted into a numerical format that computers can read.
Some prerecorded programs, such as game shows, are produced from beginning to end, in the manner of a stage play. They are produced straight through in the television studio and recorded for later broadcast. The director reviews the finished recording, and editors correct any major errors in it. Then, the recording is played when the program is scheduled for broadcasting.
Adding music and sound effects.
Most programs include music. A producer and director may decide they need an original musical composition for their show. If so, the producer hires a composer. The composer meets with the producer and director to discuss the theme, mood, and dramatic high points of the program. Composers then develop a number of musical compositions to fit with specific portions of the show. Often, producers and directors use existing music for their programs. To do so, they must get permission and pay a fee to the original composer or to the company that holds the copyright on the music.
The producer hires musicians and a conductor to perform the music. They often record the music after the video is recorded.
As the composer prepares and records the music, the sound editor adds sound effects and background noises. Then, technicians blend the music and other sounds and combine them with the rest of the program. For example, a scene of two people sitting in an automobile might require a technician to mix the sounds of the people’s conversation with recorded sounds of the automobile engine, outside traffic, and background music.
Adding visual effects
is mostly done using computer technology. Some effects, for example, provide interesting transitions from one scene to another. Instead of simply switching frames, images may fade away or transform into other images. Two important techniques are the dissolve and the wipe.
The dissolve is a gradual change from one picture to another in which the two pictures overlap briefly. Directors use the dissolve to move smoothly from scene to scene and, sometimes, to indicate a passage of time.
A wipe is a transition effect in which one picture seems to push another picture off the screen. A wipe stopped halfway is called a split screen. TV productions use the split-screen technique to show scenes from two different places at the same time.
Compositing (sometimes called matting or keying) is a technique that can be used to change the background in a scene. It may also be used to show text over a scene. For example, a camera may shoot a person standing in front of a bright blue or green background. Electronic equipment then replaces the solid blue or green background with an image from another camera. By using this technique, it appears that the person is standing in front of a new background. TV productions use this technique to place weather reporters in front of maps.
Technicians use digital video effects systems to create a variety of other manipulations, including shrinking pictures and changing colors in a scene. Character generators and video paint boxes are electronic devices that can generate letters or pictures. TV productions use these devices to create a variety of materials, including advertisements and weather maps.
Computer-generated imagery (CGI) artists can create realistic-looking video of almost anything, such as huge explosions, natural disasters, or supernatural creatures. Computer programs enable TV crews to mix such video with natural video captured by television cameras.
Live telecasts.
Some kinds of TV programs are usually telecast live. They include newscasts, sports competitions, and special events coverage.
Putting a live show on the air requires the combined efforts of many skilled workers. Much of the work takes place in a control room, which contains the equipment needed for the technical parts of the show’s production. When doing a remote telecast, broadcasters park a remote truck containing control-room equipment near the place of the telecast.
The control room.
During a live television program, scenes from each camera shooting the program appear on monitors in the control room. This bank of monitors looks like a collection of TV screens, each showing a different image. Pictures from other video sources, including filmed commercials, video recordings produced by reporters in the field, and images bearing titles, also appear on monitors. The director and his or her staff determine which of these images will be shown at various points in the broadcast. The picture that is on the air at any given time appears on a monitor called the program monitor, line monitor, or master monitor.
A program may also include sounds and music from several sources. Decisions about sounds are made in the control room as well.
An important piece of equipment in the control room is the switcher or vision mixer. It enables a technician called the technical director (TD) or vision engineer to select any of the cameras and any other picture source. The switcher makes it possible to cut (switch instantly) from one picture source to another, or from the program to commercials. The switcher also enables the technical director to produce a variety of special effects.
Recording the program.
Broadcasters usually record live programs at the same time as they telecast them. This allows the broadcasters to rerun all or parts of a show later. For example, recorded highlights of live telecasts of speeches by world leaders are often shown later on newscasts. Recorded video of live sports events allows sportscasters to rerun and analyze key plays immediately after they happen. This process is called instant replay. Coaches may also use instant replay to challenge rulings the referees have made.
The U.S. television industry
The popularity of TV programs in the United States created a huge television industry in a short time. In 1946, there were only six television stations in the United States. By 2020, the country had more than 1,700 stations. A majority were commercial stations, and the rest were public stations.
The number of TV stations accounts for only part of television’s impact on the American economy. The manufacture and sales of television sets and broadcasting equipment became big businesses because of the rise of television. In addition, broadcasting, manufacturing, and sales created thousands of new jobs.
The national networks.
A majority of all commercial television stations in the United States are affiliates of one of four major national networks—ABC, CBS, Fox, and NBC. Commercial broadcast television often is referred to as network television or the networks. An affiliate agrees to carry programs provided by a network. Smaller networks, including the CW and MeTV, each broadcast several hours of programming per week. The Spanish-language networks Univision and Telemundo supply programming to stations and cable systems throughout the United States.
The networks create some of their programs and buy others from partner studios and independent producers. A network pays its affiliates for carrying the programs. Sponsors, in turn, pay the networks for showing their commercials on the stations.
The success of cable television has significantly reduced the average audience size of the broadcast networks. Nevertheless, such networks still attract larger national audiences than cable TV, magazines, newspapers, internet services, or any other advertising medium. As a result, advertisers are willing to pay high prices to advertise on network television. A network’s success depends on its ability to select programs that attract large audiences. The bigger a program’s audience, the more money sponsors will pay for the right to show commercials during that program.
Choosing new programs.
The TV executives who choose network programs know that famous entertainers and championship sports contests usually attract large audiences. But these executives cannot be certain how many viewers other shows will draw. The chance of launching a successful new program is small, and the costs of programming are high. When a new program fails, a network may lose millions of dollars, so network executives must be careful about their program choices.
Network executives may be helped in choosing programs by specialists in audience research. Such specialists collect data about people’s interests and the kinds of programs they like. These specialists also gather the responses of audiences invited to view special pilot (test) episodes of new programs. However, such research has limited success in predicting a program’s popularity for various reasons. For example, an audience’s response to a single episode of a program might differ from its response to a series. As a result, network executives must ultimately rely on their own intuition and experience in choosing programs.
Measuring a program’s success.
Network executives are most concerned about the programs they show each evening during prime time—that is, the evening hours, when television draws the most viewers.
The success of a program is measured in ratings and share. Ratings measure the percentage of all households equipped with television that are tuned to a particular program. Share measures the percentage of households with a set switched on that are tuned to a particular program.
Nielsen Media Research is the most important national audience measurement service. It provides television executives and advertisers with information about ratings and share and with demographic data about audiences. Demographic data describe the makeup of an audience in terms of gender, age, income, education, race, place of residence, and other features.
Advertisers are often willing to pay more for selected types of viewers, such as women 18 to 49 years old. Advertisers believe that these viewers are especially important because they often make many of the purchasing decisions in the home. Younger viewers are also important to some advertisers because they spend more money on goods advertised on TV and may be more likely to try new brands. Viewers over the age of 50 are thought to be less influenced by advertisements on TV. Network programmers choose offerings that will appeal to the advertiser’s most desired demographic.
A national audience survey typically consists of tens of thousands of households that are paid a small fee. The viewing habits in these households supposedly reflect the habits of the entire nation. The most advanced device to measure a TV audience is the People Meter, which resembles a TV remote-control unit. Household members each press an assigned key on the meter to indicate who is watching TV. In this way, the People Meter registers the demographic data of a program’s viewers for advertisers. Advertising rates are based on measurement of commercial viewership, rather than program viewership. Portable People Meters can be used to measure TV viewing outside the home. Networks usually cancel a series that receives low ratings, sometimes after only a few episodes.
Such video-on-demand streaming services as Netflix and Hulu also collect their own extensive data on the viewership of their programs. However, they rarely share such information with the public.
Commercial stations.
Hundreds of local commercial stations operate in the United States. About three-fourths of them are affiliates of the four major networks. The rest operate independently or as affiliates of smaller networks.
An affiliate carries many hours of network programs daily. Affiliates fill the rest of their schedules with programs they purchase and with local productions. Locally produced news shows are among affiliates’ most profitable types of programming.
Syndicated programming.
Most non-network programs are old movies, talk shows, game shows, and reruns of old network shows. These programs are syndicated—that is, sold to the stations individually by independent organizations called syndicators. Affiliates or independent stations buy syndicated programs rather than produce their own programs because it is far less expensive. In addition, syndicated programs are generally well known.
Production companies may create television series for original distribution through a system known as first-run syndication. The most popular and profitable first-run syndication programs are game shows, talk shows, and reality courtroom programs.
First-run syndication often uses an arrangement called barter sales. Under this arrangement, individual stations do not pay for the program. Instead, the station agrees to run the show and sell local commercial spots. The syndicator keeps the rest of the advertising time and sells it to national advertisers. By eliminating the network, a syndicator can make a greater profit from a popular program. A greater risk of failure falls on the producer and syndicator, however, because there is no guarantee that the local stations will buy new programs that the syndicator develops.
Advertising.
Both affiliates and independent stations sell air time to advertisers to cover the costs of their programs. Brief television commercials appear between programs and during breaks in programs. Most urge viewers to buy a product, patronize a business, or subscribe to a service. At election time, many political candidates buy advertising time on television to try to persuade people to vote for them.
Product placement is a way to promote products and brands within television programs. Examples include fictional characters using real-life products, and reality show contestants competing for prizes from commercial sponsors. Product placement increased after the introduction of DVR’s and ad-free streaming services that enabled viewers to skip or avoid commercial breaks.
Infomercials are television programs created expressly to promote products. Many commercial stations fill time slots not suitable for original or syndicated programming with these long commercials. On a typical infomercial, a celebrity or other spokesperson demonstrates and endorses a product. Direct appeals to purchase the product over the telephone or the internet, or through the mail, are often part of the program.
A small percentage of TV advertising provides a public service announcement (PSA). PSA’s may include messages urging people to drive carefully, to avoid drugs, or to stay in school. They also include announcements about local community activities.
Criticism of commercial television.
Commercial television attracts huge audiences. Each evening, tens of millions of people in the United States watch news and other programs on the major TV networks and on other commercial channels. Even so, many people criticize commercial TV. They say that it provides too many programs designed only to entertain, and not enough shows that inform, educate, or furnish cultural enrichment. Critics also claim that much of the entertainment is of poor quality because it aims at the largest possible audience. They express concern that much commercial programming has an excess of violence and sexual content. They also criticize newscasts for being too brief to provide thorough coverage of the news.
The people responsible for deciding what appears on commercial television respond to such criticisms by pointing out that commercial TV must sell advertising at high prices. To do so, the programs must attract large numbers of viewers. Many more people watch popular shows and brief news reports than watch culturally enriching shows and in-depth news analysis.
Public stations.
Several hundred public TV stations operate in the United States. These stations create many of the programs they show, and buy programs from independent producers. Often, a program created by one public station is carried by many others. An agency called the Public Broadcasting Service (PBS) serves as a distributor of locally produced public programs.
Public stations are nonprofit organizations, but they need money to cover their production and operating costs. A significant part of a station’s funds come from viewer contributions. Businesses and foundations also help support public television. Local and state taxes help pay for many public stations. Stations also receive funding from the Corporation for Public Broadcasting.
The Corporation for Public Broadcasting, created by Congress in 1967, gets most of its funds from the federal government. The corporation helps public stations serve their communities through grants for programming and technical facilities. It also finances the production of programs distributed by PBS and sets policies for a national public broadcasting service. See Corporation for Public Broadcasting.
Cable and satellite systems
bring television to the home by means of cables or through the air to a satellite receiving dish. Most programming for cable and satellite television is provided by national program suppliers called programming services. Each service tries to appeal to a particular demographic group or specializes in a particular type of programming. For example, Lifetime and BET (Black Entertainment Television) are services that try to appeal to women and African Americans, respectively. Cable News Network (CNN) and Comedy Central are services that supply a particular form of programming.
Programming services earn money by selling advertisements and by charging subscription fees. Many channels run infomercials in program-length time slots. Nonprofit cable channels offer public affairs programming without advertising.
For picking up a programming service, the local cable system or satellite supplier pays a charge for each household that subscribes to its service. The supplier passes on this cost to the consumer. Subscribers pay a monthly fee based on how many and which channels they want to be able to access.
Premium channels—for example, HBO (Home Box Office) and Cinemax—usually do not carry advertising. Their programming may include recent motion pictures, live sports events, music concerts, and documentaries, as well as their own original movies and series. Some premium channels offer movies and sports events to the subscriber on a pay-per-view basis. A consumer transmits a special order for the programming, and the charge is applied to the next month’s service bill.
Video-on-demand streaming services
allow viewers to watch movies and television programs on TV’s and other internet-connected devices. They may feature their own original content as well licensed content, such as network and cable TV programs. Some streaming services charge a subscription fee and are commercial-free. Others allow free access but include advertisements. Popular streaming services include Amazon Prime Video, Hulu, and Netflix, among others.
Regulating U.S. television.
The Federal Communications Commission (FCC), an agency of the federal government, regulates television broadcasting in the United States. The television industry also regulates itself through a voluntary ratings system.
Government regulation.
The FCC issues broadcasting licenses to stations and assigns frequencies on which the stations must broadcast. These regulations are needed to maintain order in the airwaves. If anyone who wanted to were allowed to broadcast and use any frequency, signals would interfere with each other and make broadcasting impossible.
The FCC also sets standards for broadcasters. The agency cannot censor programs, but it has the power to take away, or refuse to renew, a station’s license if the station violates the standards too much. The FCC expects stations to avoid obscenity and pornography in their programs because television is widely available to children. The agency requires stations to provide public services and programs designed to meet the needs of their local communities. Another FCC standard requires television broadcasters to give equal time to all legally qualified candidates for public office. In addition, the FCC, along with the Federal Trade Commission (FTC), evaluates truthfulness in TV advertising. The FCC does not regulate content on cable, satellite, or streaming television.
The U.S. Congress can also regulate broadcasting. For example, it passed a law prohibiting cigarette advertising on television. The law was based on the government’s conclusion that cigarette smoking is harmful to health. In 1996, Congress passed the Telecommunications Act, which required all new TV sets to contain a computer chip that enables parents to block programs they consider inappropriate for their children. The television industry rates programs on their explicitly violent or sexual content or other mature content. The chip, popularly known as the V-chip (for violence), blocks out programs as instructed according to the rating.
Broadcasters generally oppose government regulations. They say regulations affecting programming interfere with their rights to freedom of expression. Most members of Congress disagree, as do many citizens’ groups. They claim that because the airwaves are public property, the government must create regulations that serve the public interest.
Self-regulation.
In 1997, under pressure from the public and from legislators, most broadcast and cable television networks adopted a voluntary content-rating system. The system received FCC approval in 1998. Its purpose is to inform viewers of the appropriate audience for a specific program based upon its content. The ratings classify programs in several categories, including TVG (suitable for all audiences), TVY7 (inappropriate for children under age 7), and TVMA (for mature audiences only). The rating may have one or more additional letters attached indicating the nature of the questionable content, such as V for violence or L for indecent language. Streaming services also use this rating system.
Under the FCC-approved system, each network or service evaluates its own programs and attaches a rating to them that is displayed at the start of the program and in all program schedules and promotions. A television with a V-chip can block viewing of programs with a certain rating. The FCC-approved ratings system is still voluntary, however, and a few television networks have instituted a different ratings system. The V-chip cannot block programs on channels not using the FCC-approved system.
Television awards
are presented each year by a number of organizations. The best-known awards, the Emmy Awards, are given by the Academy of Television Arts and Sciences and by the National Academy of Television Arts and Sciences. The two academies recognize achievements of the preceding year in various fields of the TV industry. Some local chapters of the National Academy also present Emmys for local achievements. The Golden Globe Awards, given by the Hollywood Foreign Press Association, recognize achievement in American television, as well as motion pictures from around the world. 
Television throughout the world
Television became popular around the world in the 1950’s and 1960’s. In the early years, most countries borrowed programs and ideas for programs from other countries, especially from the United Kingdom and the United States. By the mid-1960’s, most TV programs were produced and watched within one country. This trend continued through the 1990’s. But local programming has been harder to sustain in some smaller countries. Such countries have come to rely on foreign programs for their television content. In most countries, no matter the source of the content, television plays a major role in people’s lives.
Beginning in the early 2010’s, video-on-demand services attracted television content and viewers from around the world. Netflix, Disney+, and iQIYI became some of the largest providers of video-on-demand television. Such services competed with traditional, nationally based television for viewers’ attention.
In Africa.
On average, countries in Africa have fewer TV stations than countries in other parts of the world. Because many African countries are poor, it is difficult to sell advertising and support commercial television productions. Many TV stations are owned by the government, but a growing number of African countries have privately owned commercial broadcast and satellite stations. Publicly funded stations receive financial support from the government and sometimes operate under political leaders’ control. In many African countries, the people do not share a common language. Thus, some stations broadcast programs in several languages.
Because many African countries are sparsely populated, cable television is expensive and satellite television is more common. Many providers of satellite TV offer hundreds of channels across the continent.
In the Middle East,
governments attempt to heavily regulate television. Subscription satellite services based in and outside the region carry dozens of local and international channels. Most of these channels have programming in Modern Standard Arabic, used to communicate across different dialects spoken in the region. The Saudi-owned Middle East Broadcasting Center (MBC) operates a number of free satellite TV channels.
Many of the most popular shows are produced in Egypt, Lebanon, and Syria. The United Arab Emirates (UAE) is also an important provider of satellite services. Dubai, the UAE’s largest city, is a major TV production and distribution center. Qatar is home to Al-Jazeera, the first global news service from the Arab world.
In Asia.
Television is a thriving industry in Asia, particularly in India and China. In India, the public television network Doordarshan operates many channels in different languages. In addition, dozens of private cable and satellite TV networks serve India’s different language regions. India’s large commercial TV industry produces programs for national and international distribution. Indian satellite TV channels are available across South Asia and in more than 100 countries around the world.
Chinese television has developed almost independently of Western TV to become regionally and globally popular. The state-run broadcaster China Central Television (CCTV) controls broadcast television, which tends to be heavily censored. Privately operated cable and satellite television offer viewers much more diverse content and perspectives.
Japan has one of the liveliest television markets in the world. The public corporation NHK operates several domestic broadcast and satellite TV stations, as well as an international television service. Private companies operate several broadcast networks and dozens of cable and satellite services. Most of the leading programs on Japanese television are produced in Japan and are also popular abroad, especially in South Korea and some Chinese-speaking areas.
The Korean Broadcasting System (KBS), a public broadcasting service, dominates television in South Korea, where it operates several broadcast and cable channels. The country also has many commercial channels. South Korean TV programs, especially idol dramas featuring popular music stars, became a global phenomenon in the 2010’s.
In Australia and New Zealand,
television consists of a mixture of public and commercial services. The largest Australian network, the Australian Broadcasting Corporation (ABC), provides national, noncommercial television service. Commercial television is available in all of Australia’s states. Television New Zealand Limited, a government-owned, commercially funded broadcaster, dominates TV broadcasting in New Zealand.
Many shows in Australia and New Zealand are imported, especially from other English-speaking countries. Both countries also have active TV production industries. Australian programs in particular are popular in many English-speaking nations and elsewhere.
In Europe,
which has a common market in audiovisual trade, much of the production and distribution of television content is multinational. Most European countries have at least one public broadcasting company and several privately owned companies. Cable and satellite services are widespread, and most of them span multiple countries. 
Although commercial television is popular, many European nations also maintain strong public broadcasting services. In Germany, Poland, Sweden, and the United Kingdom, for example, audiences pay taxes and user fees that support high-quality public programming. Large public broadcasters in Europe include the British Broadcasting Corporation (BBC), Arbeitsgemeinschaft der öffentlich-rechtlichen Rundfunkanstalten der Bundesrepublik Deutschland (ARD) in Germany, and France Télévisions.
European Union (EU) regulations require that a majority of programs in member states come from European producers. This helps to ensure the vitality of European TV production industries.
Some eastern European countries outside the EU—for example, Belarus, Russia, and Ukraine—also have a mixture of public and private television. However, even private TV services tend to be owned by media figures with close ties to politicians, and the channels exhibit little independence in their content.
In Latin America,
most countries have a mixture of state-owned and privately owned television stations. In less developed or smaller countries, such as Guatemala or El Salvador, it is difficult to develop strong commercial television industries. Thus, the government plays an important role in television. Larger, wealthier countries such as Brazil and Mexico have developed large TV industries with successful commercial networks. The Brazilian television network Globo is one of the most prosperous networks in the world. It distributes its original content globally. 
Mexico’s largest network is Televisa. One of the most popular types of programs produced by Televisa is a kind of television serial called a telenovela. Like a novel, each telenovela is a story with a beginning, middle, and end. Telenovelas run for a shorter time than U.S. television series, which may continue for many years. Televisa’s telenovelas are popular in many other Latin American countries and around the world.
In Canada.
The Canadian Broadcasting Corporation/Radio-Canada (CBC/Radio-Canada), a publicly owned corporation, is a major force in Canadian television. It operates two national broadcasting networks—one in English and the other in French. It also runs some cable and satellite channels. The CBC North service and the publicly funded Aboriginal Peoples Television Network offer programming in Indigenous (native) languages.
Canada’s largest privately owned TV networks include the CTV Television Network and the Global Television Network, both of which broadcast in English. Canadian homes also receive most U.S. network programs broadcast from stations near the Canada-U.S. border.
Several Canadian cities have become important centers for the production of Canadian and U.S. television programs. A number of Canadian TV series have become popular worldwide. These include “The Kids of Degrassi Street” and several other “Degrassi” series that aired from about 1980 through the 2010’s.
International television awards
include the Banff World Media Festival Rockie Awards, the International Emmy Awards, the Prix Italia, and the Rose d’Or (Golden Rose). Television producers from many countries submit programs for judging for these awards.
History of U.S. television broadcasting
The start of broadcasting.
Many experimental telecasts took place in the late 1920’s and the 1930’s. In the United States, CBS and NBC were leaders in experimental telecasts. The British Broadcasting Corporation (BBC) performed experimental telecasts in the United Kingdom. But World War II (1939-1945) and economic problems afterward caused the BBC to abandon TV experiments. The United States moved far ahead of the rest of the world in TV broadcasting.
In 1936, the Radio Corporation of America (later RCA Corporation), which owned NBC, installed television receivers in many homes in the New York City area. NBC’s New York station began experimental telecasts to these homes. A cartoon of Felix the Cat was its first program. NBC established the first regular TV broadcasts in the United States in 1939. The United States entered World War II in 1941. Television broadcasting was suspended until after the war ended in 1945.
The television boom.
CBS and NBC resumed broadcasting shortly after the war. Two other networks, the DuMont Television Network and ABC, soon began operations. All four networks were based in New York City. At first, telecasts reached only the Eastern Seaboard between Boston and Washington, D.C. But by 1951, they extended coast-to-coast. Television stations sprang up throughout the country. Entertainment, news, special events, and sports contests replaced the simple, largely experimental, prewar shows. The DuMont network failed to earn consistent profits and stopped broadcasting in 1956. The other three networks dominated the TV industry until the late 1980’s. 
Americans became fascinated with the idea of having such a wide range of visual events available in their homes. The demand for TV sets became enormous. In 1945, there were probably fewer than 10,000 sets in the country. This figure soared to about 6 million in 1950, and to almost 60 million by 1960. In TV’s early days, people who had no set often visited friends who had one just to watch television. Also, many stores placed television sets in windows, and crowds gathered on the sidewalk to watch programs.
Early programs.
Milton Berle became the first television entertainer to attract a huge nationwide audience. His show, “The Texaco Star Theater,” was filled with zany comedy routines. It ran from 1948 to 1956 and often attracted 80 percent of the TV audience. “I Love Lucy,” starring Lucille Ball, went on the air in 1951. This early situation comedy also attracted a huge following. Westerns, such as “Gunsmoke” and “Have Gun Will Travel,” became popular in the mid-1950’s. Other popular early entertainment programs included Ed Sullivan’s variety show, “The Toast of the Town”; the comedy-variety program “Your Show of Shows,” starring Sid Caesar; professional wrestling matches; and quiz shows offering prizes of thousands of dollars.
Coverage of special events did much to widen TV’s appeal. In 1951, TV broadcast the Kefauver hearings, in which U.S. Senator Estes Kefauver and his Senate committee questioned alleged mobsters about organized crime. In 1954, TV covered the Army-McCarthy hearings. Viewers watched spellbound as Senator Joseph R. McCarthy accused the U.S. Army of “coddling Communists,” and the Army charged McCarthy’s staff with “improper conduct.”
A major scandal hit TV in 1959, when several losing contestants on quiz shows revealed that the shows’ producers had helped some contestants answer questions. The scandal led to industry reforms, but it also encouraged criticisms of other aspects of television. Researchers expressed concern about the effect of TV on children. Civic groups complained about violence and ethnic stereotypes. Government leaders claimed TV needed to offer more news and information programming. As a result, all three major networks began to expand their news and public affairs departments.
The 1960’s
opened with a milestone of television broadcasting. During the fall of 1960, presidential candidates John F. Kennedy and Richard M. Nixon faced each other and the nation in a series of TV debates. It was the first time presidential candidates debated on TV. Many people believe the debates made an important contribution to Kennedy’s victory in the 1960 election.
Popular entertainment remained the major part of television’s coverage during the 1960’s. But TV also reflected the social turmoil in American life at that time. President Kennedy was assassinated on Nov. 22, 1963. Two days later, millions of TV viewers witnessed a startling scene. In full view of TV cameras, Jack Ruby shot and killed accused Kennedy assassin Lee Harvey Oswald as the police were moving Oswald between jails. 
Beginning in the mid-1960’s, television regularly brought viewers battle scenes from the Vietnam War (1957-1975). The conflict was sometimes called “the first war to be fought on television.” In addition, television viewers watched war protesters demonstrate, sometimes violently, and witnessed bitter debates over the war policy of the United States. Civil rights protests by African Americans and other minority groups also became part of TV coverage.
During the early years of television, broadcasters largely avoided such controversial themes as abortion, alcoholism, divorce, drug abuse, political satire, prejudice, and sex. In the late 1960’s, however, broadcasters found that they could deal with such controversial themes and still draw large audiences, especially in younger age groups. The show “Rowan and Martin’s Laugh-In,” which included much political and sexual humor, became the top-rated show of the late 1960’s.
The 1970’s
established television entertainment as a reflector, and often a leader, of public opinion and social customs. Such programs as “All in the Family” and “The Mary Tyler Moore Show” and many movies made for television examined controversial social issues. The popular children’s program “Sesame Street” proved that TV could be an entertaining form of education. On such investigative news shows as “60 Minutes” and “20/20,” network news departments reported on dramatic stories that drew strong ratings. Many professionals in the television industry believed that TV could be both popular and socially beneficial.
In the late 1970’s, broadcasters began to present more made-for-TV movies, miniseries (dramas in several installments), and other special programs. The extremely popular miniseries Roots traced the history of an African American family from slavery to freedom. It sparked widespread discussions about racial equality and about television’s responsibility as an agent of change.
The 1980’s and 1990’s
saw broadcast television adjust for changes in national taste and for competition from new networks and from cable TV. Comedy programs used more sexual humor. Such shows were led by “Married … with Children,” which featured a family whose members openly expressed dislike for one another. This show was a reaction to the model family represented by “The Cosby Show,” the most successful comedy of the mid-1980’s. “Married … with Children” became a hit for Fox, a national network established in 1986.
Television producers transformed the hourlong drama in the 1980’s. Such dramas began incorporating more storylines and shifting focus among different characters. They also showed more graphic violence, sexual situations, and coarse language. Notable programs of this type included the police drama “Hill Street Blues” and the medical drama “St. Elsewhere.” Many people believed television had gone too far by showing too much sex and violence.
As cable TV and smaller broadcast networks attracted more viewers, the major broadcast networks struggled to find and keep hit shows. This resulted in tremendously high salaries and fees for the talent and studios associated with big hits. For example, NBC paid Jerry Seinfeld, the star and producer of the sitcom “Seinfeld,” $1 million per episode for its 1997-1998 season. And in 1998, NBC agreed to pay the producers of the medical drama “ER” a record $13 million to air each new episode.
Faced with declining viewership and the high cost of hit shows, broadcast networks sought less expensive forms of programming. They turned to reality television and news programs. Reality TV shows actual events, sometimes planned, and usually features nonactors. A pioneering reality program was “Cops,” which followed police officers through their day. Another was “America’s Funniest Home Videos,” which featured home movies submitted by ordinary people. The networks also added such prime-time newsmagazine shows as “Dateline NBC” and “PrimeTime Live” to their schedules. In the late 1990’s, major networks focused increasingly on game shows. In 1999, ABC launched “Who Wants to Be a Millionaire?,” which shot to the top of television ratings.
In the 1990’s, the great number of channels available on cable and satellite television gave birth to narrowcasting. This practice targets specific interest groups, and demographic groups preferred by advertisers, rather than trying to capture large audiences.
The early 2000’s
saw viewership of the major broadcast networks continue to decline. Although such networks still drew the largest audiences, they drew smaller audiences than in the 1970’s. As the number of cable and satellite channels continued to grow, they attracted more and more viewers. Successful cable channels also faced competition from new cable channels that targeted more specialized audiences. 
Increased competition created pressure for network and cable television to develop attractive programs. Dramas became lavish productions at the major broadcast networks. Such shows as “Lost,” “24,” and “CSI” set high standards for acting, writing, and production. Cable channels, including TBS, FX, and AMC, also began to invest in original dramas. News programs and reality shows also played an important role on prime-time network television. Popular reality shows included “Survivor,” a contest to survive in the wilderness, and “American Idol,” a singing competition. “American Idol” attracted some of the largest audiences in television history. 
The early 2000’s also saw the introduction of streaming television. The development of smart TV’s that could connect with the internet and of such streaming devices as Apple TV and Roku enabled viewers to watch streamed content on a TV screen. YouTube, a video-sharing website featuring user-generated content, was launched in 2005. It became so popular that some TV networks used it to promote their programs.
The 2010’s.
The growth of video-on-demand streaming services in the 2010’s transformed the TV industry. Netflix, which first offered a streaming service in 2007, became dominant in the field. It began presenting original programming in 2013 with the drama series “House of Cards.” Other popular Netflix series included “Orange is the New Black,” “BoJack Horseman,” and “Stranger Things.” Other streaming services also began creating their own original programs. The release of entire seasons of original series at once allowed for binge watching (watching several episodes in one sitting).
Such streaming services as Amazon Prime Video, Hulu, and Netflix appealed to general audiences. Other services targeted viewers with particular interests. For example, Acorn TV and BritBox featured British programs, Shudder featured horror programs, and Crunchyroll featured anime. In addition, major entertainment companies developed their own streaming services, including Disney+, HBO Max, and Peacock, named for the NBC logo. Such live TV streaming services as Sling TV and YouTube TV provided an alternative to cable television by offering streaming access to bundles of broadcast and cable TV channels.
Network television ratings declined as viewers split their attention among many entertainment outlets. In addition to streaming television, such new social media services as Instagram and TikTok drew the attention of viewers. Broadcast networks relied more upon professional sports and other live events to retain viewers.
Cable channels made strides in representing racial diversity with such series as “Atlanta,” “Insecure,” and “Pose.” The HBO series “Game of Thrones” became extremely popular and won many awards. Cable news channels CNN, Fox News, and MSNBC also drew many viewers during the controversial administration of U.S. President Donald J. Trump.
Effects of television
In many countries, television ranks as a major influence on life. It affects the way people spend their time and what and how they learn. Some authorities believe TV has a greater influence on young people than on adults. Television also affects politics, sports, and the other media.
Effects on leisure time.
Throughout the industrialized world, watching television is one of the most time-consuming leisure activities among adults. Some critics say that television viewing takes time away from other activities, such as reading, conversation, social gatherings, and exercise.
Effects on learning and perception.
Television can contribute greatly to what viewers learn. It may benefit people by widening their experience. On the other hand, TV also may contribute to harmful impressions of the world.
Enriched experience.
No communication system has ever provided so many people with as wide a range of new experiences as television has. Without leaving their homes, TV viewers can watch government officials perform important functions and see how people in far-off lands look and live. Television takes viewers to deserts, jungles, and the ocean floor. A TV viewer can see how a famous actor performs the role of Hamlet, and how top comedians draw laughter. Television gives its viewers a glimpse of real-life tragedy, such as when it covers the victims of war, natural disasters, and poverty. It also captures moments of great triumph, such as when astronauts first set foot on the moon.
Harmful impressions.
Many social scientists believe that people will likely form false impressions from watching a great deal of television. One of these impressions is that many people are better off than they are. Another is that the world is an unfriendly place, filled with untrustworthy people and risky circumstances.
Television programs often show people leading more glamorous lives and owning more material goods than most viewers. In addition, TV commercials constantly urge viewers to buy things. Many sociologists believe that as a result, the material expectations of TV viewers are raised, sometimes to an unrealistic level. One harmful effect results when people fail to achieve the success they see on TV and become dissatisfied or bitter.
Some social scientists claim that television violence encourages some viewers to believe the world is a more violent place than it actually is. As a result, some people may become overly suspicious and fearful of others. But other scholars point out that storytelling throughout history has often featured tales of struggle, violence, and revenge. These scholars suggest that like these stories, television places violence in contexts that provide opportunities for moral reasoning.
Effects on society.
Television has brought about major changes in several parts of society, including politics, sports, and motion pictures and radio.
Politics.
Television plays an important role in national elections. Before TV, candidates for president, prime minister, or other high office tried to make as many personal appearances and speeches as possible. Today, candidates reach more voters through a single TV appearance than through all the campaigning they do in person.
In some countries, including the United States, candidates can buy TV time for a spot announcement. Spot announcements are political messages that generally last 30 seconds. In some other countries, such advertisements are illegal. Instead, broadcasting authorities allow the main political parties some free television time to present their policies and points of view.
Television does much to promote interest in politics and political issues. But political advertising and news coverage on TV also draw criticism. In countries where political advertising is allowed, critics say spot announcements are too short to allow candidates to discuss issues. Instead, candidates use the time to present oversimplified statements. Critics also claim that, because television time is so expensive, TV campaigning gives unfair advantage to the candidates with the most money. Critics are also concerned that news programs often televise only a sentence or two, called a sound bite, from a candidate’s remarks. These short quotations contrast sharply with the long political speeches that are typical of traditional in-person campaigning. Critics also note that TV news coverage focuses on the dramatic “horse race” competition between candidates rather than on important issues.
Professional sports
have long attracted millions of spectators yearly. But many more millions now watch the events on television. Television networks and stations pay leagues and team owners huge amounts of money for the right to televise games. This money, in turn, helps fund the huge salaries of professional athletes. Television also helps increase the popularity of sports. For example, the popularity of American football has soared largely because of television. Other sports—such as automobile racing, golf, ice skating, and soccer—have also gained larger audiences through television.
Other forms of entertainment.
From the 1920’s through the 1940’s, films and radio were the chief forms of entertainment for millions of people. Many families went to the movies at least once a week. They listened to comedies, dramas, and other entertainment programs on the radio almost every night. The rise of TV in the 1950’s caused a sharp drop in movie attendance, but the motion-picture industry eventually rebounded. It did so by focusing on the production of films with special effects that are hard to achieve on television.
Radio entertainment changed completely after TV became a part of everyday life. Almost every radio entertainment show went off the air. Recorded music became the chief kind of radio programming, and radio rebounded. Today, radio faces competition with the internet, which has become the leading outlet for recorded music.
National magazines also suffered after the arrival of television. Some national magazines that had circulations of millions went out of business when advertisers shifted large amounts of money to television. The industry revived its popularity by emphasizing magazines aimed at special audiences.
Effects on young people.
Young people can learn a great deal about the world from television news, documentary, and information programs. TV often provides young people with the opportunity to observe adult conversation and behaviors in a variety of social settings. Young viewers can also watch television programs that reflect upon difficult moral choices.
Parents have long been concerned about the amount of time young people spend watching TV. Some studies suggest that children imitate violent behaviors they see on TV. Other studies have linked watching a great deal of television with poor performance in school. However, these studies do not prove that TV viewing actually causes students to perform poorly. Many other factors—such as family, religion, and school—also play significant roles in shaping the behaviors of children.
Creating television signals
The first step in sending pictures and sound is changing the light and sound waves from a scene into a television signal. This signal begins when light from the scene enters a television camera. The camera changes the light into electronic signals. At the same time, a microphone picks up the sounds and changes them into electronic signals. Television engineers call the signals from a camera video and the signals from a microphone audio.
This section describes how a TV camera creates video signals. TV audio signals are created in the same way as radio signals. For information on this process, see Radio.
To capture motion, the television camera shoots many pictures every second, just as a motion-picture camera does. A TV camera divides a picture into hundreds of thousands of tiny parts by a process called scanning. As the camera scans the picture, it creates electronic signals from each tiny part of the picture.
TV stations in most countries broadcast composite color video signals. These video signals produce a color picture when received on a color television set, and they produce a black-and-white picture on a black-and-white TV set.
Color TV uses the three primary colors in light—red, blue, and green—to produce full-color pictures. The proper mixture of these three colors can produce any color of light. For example, a mixture of red and green light produces yellow light. Equal amounts of red, blue, and green light produce white light.
In producing a composite color video signal, the TV camera must capture the image of the scene being telecast, create video signals from the image, and encode the color signals for transmission. To perform these tasks, a television camera uses a lens, a system of mirrors and filters, image sensors, and complex electronic circuits.
Capturing the image.
The lens gathers the image of the scene in front of the camera. Like the lenses in other cameras and the human eye, the TV lens focuses the light from the scene to form a sharp image. This image contains all the colors of the scene. To produce color signals, however, the camera must split the full-color image into three separate images, one for each primary color.
Most TV cameras use two dichroic mirrors to split the image into the primary colors. These mirrors, like the color filters used in photography, reflect light of only one color and let other colors through. The first mirror reflects the blue image and allows red and green light to pass through. The second mirror reflects the red image, leaving only the green image. Other mirrors reflect each image to a separate image sensor. In many cameras, this color separation is done by color filters and prisms contained in a small compartment called the prism block.
Creating the video signals.
An image sensor changes the light image into electronic signals. Most high-quality color cameras have three sensors. These sensors create a separate electronic signal for each of the three primary colors. Many small, lower-quality, portable cameras are equipped with a single sensor. This sensor has many thin red, blue, and green filter stripes on its surface. The stripes divide the light into the three primary colors, and the sensor then converts each of the colors into a separate signal.
Two types of image sensors may be used in television cameras. Tube cameras contain improved versions of a vacuum tube called a vidicon. Solid-state cameras, also called CCD cameras, contain solid-state electronic sensing mechanisms called charge-coupled devices (CCD’s). Solid-state cameras are smaller, lighter, and more reliable than tube cameras. In the 1990’s, solid-state cameras started to replace tube cameras, which were first developed in the 1930’s. Solid-state cameras are now the industry standard in many countries.
Tube cameras.
A vidicon tube has a glass faceplate at its front end. In back of the faceplate is a transparent coating called the signal plate. Another plate, known as the target, lies behind the signal plate. The target consists of a layer of photoconductive material, which conducts electric current when exposed to light. At the rear of the tube is a device called an electron gun.
Light from the image reaches the target after passing through the faceplate and signal plate. The light causes negatively charged particles called electrons in the photoconductive material to move toward the signal plate. This movement leaves the back of the target with a positive electric charge. The strength of the positive charge on any area of the target corresponds to the brightness of the light shining on that area. The camera tube thus changes the light image gathered by the lens into an identical electric image of positive charges on the back of the target.
The electron gun shoots a beam of electrons across the back of the target. The beam moves across the target in an orderly sequence called a scanning pattern. As the beam moves across the target, it strikes areas with different amounts of positive charge. The electrons from the beam move through the target and cause an electric current to flow in the signal plate. The voltage of this current changes from moment to moment, depending on whether the beam is striking a bright or dim part of the image. This changing voltage is the video signal from the camera tube.
Solid-state cameras
use an electronic sensing mechanism called a charge-coupled device. A charge-coupled device is a silicon chip with tiny, square photoconductive elements (parts) arranged on its surface. Light falling on an element (also called a pixel) causes electrons to flow into the element’s capacitor, a device that stores an electrical charge. As more light falls on the element, more electrical charge accumulates in the capacitor. The CCD thus changes the light coming through the camera lens into an identical electric image. The CCD then reads out the image by releasing the charge stored in each capacitor to cause an electric current to flow. This current is the video signal from the CCD. The CCD releases the capacitor charges according to the scanning pattern.
Camera scanning patterns.
During the first 50 years of television, most television systems used interlaced scanning. A scanning beam scans every other line of the picture, beginning at the top left corner of the screen as seen by a viewer. After it reaches the bottom right corner, the beam returns to the starting point and scans the remaining lines, again from top left to bottom right.
The scanning pattern of TV cameras in North America, most of South America, and Japan and several other Asian countries was developed in the United States as the NTSC (National Television System Committee) system. It is made up of 525 lines (262 1/2 odd-numbered and 262 1/2 even-numbered lines). The camera completes one field each time it scans 262 1/2 lines. Two fields make up a complete television picture, called a frame. The camera scans so quickly that it produces 30 complete frames in a second. This speed is fast enough so the picture shows moving images smoothly. The scanning patterns of TV cameras in other parts of the world use one of two other systems: PAL (phase alternating lines), which originated in Germany, and SECAM (système electronique couleur avec mémoire), which originated in France. Both systems display 625 lines per frame at 25 frames per second.
Digital television, a new way of broadcasting TV signals developed in the 1990’s, has introduced new scanning systems. Cameras have been developed that can scan 480, 720, or 1,080 lines. Some use interlaced scanning, but others use progressive scanning. Progressive scanning captures the image with a single scan per frame. Cameras with more scanning lines can improve picture quality dramatically.
In all the scanning systems, each of the three image sensors converts one of the three primary colors to an electronic signal by means of the scanning process. Wires carry the signals to electronic circuits in the camera that amplify (strengthen) them. The three signals then go to the encoder.
Encoding the color signals.
The encoder then combines the chrominance and luminance signals and adds a color burst and synchronizing signals. The color burst enables a color TV set to separate the color information in the chrominance signals. This information, along with the luminance signal, produces a full-color picture on the TV screen. The synchronizing signals enable the TV set to repeatedly return to the beginning of each scan line and field without interruption.
Transmitting television signals
Television signals must be transmitted to the television receiver. Some signals are broadcast through the air. Engineers at a TV station use a device called a transmitter to produce a TV signal from separate audio and video signals. The signal is then carried by wire to an antenna and broadcast as an electromagnetic wave. Such waves travel through the air at the speed of light, about 186,282 miles (299,792 kilometers) per second. But the signal weakens the farther it travels. The signal can be received clearly only up to a distance of about 75 miles (120 kilometers). To send TV signals farther, other means of transmitting must be used. These include coaxial cables and fiber-optic cables, microwaves, and satellites.
Broadcasting.
A wire called the transmission line carries the signal to the transmitting antenna. This antenna releases the signal into the air. Television stations erect their antennas on high buildings or towers so that the signal can reach as far as possible.
Throughout the world, television stations broadcast in the very high frequency (VHF) and ultrahigh frequency (UHF) bands. VHF refers to signals with a frequency from 30 to 300 megahertz (million vibrations per second). UHF signals have a frequency from 300 to 3,000 megahertz.
Digital broadcasting systems are replacing those that use analog signals. Analog signals use a continuously varying form to represent and transmit sound or pictures. Digital technology converts television signals into sequences of 1’s and 0’s—that is, the same numerical code used by computers. Each of the 1’s and 0’s is called a bit, which is short for binary digit. Digital systems provide stronger and more reliable signals than analog technologies. Digital signals are less likely to be disrupted by electrical interference from appliances and storms or by reflections from tall buildings and aircraft.
Digital systems also improve TV pictures by making it possible for television signals to carry more information. Digital systems use a technique called data compression that removes unnecessary information from the signal. These systems can fit more information into existing channels. Digital technology can also check for and correct errors in transmission, resulting in a better picture.
With the conversion to digital television, the FCC has given broadcasters new frequencies to use for their digital broadcasts. Each channel carries a stream of 19.39 megabits of digital data. A megabit is 1 million bits. Broadcasters can use the stream of digital data to transmit one high-quality television signal, or they can divide it into a television channel and a group of subchannels. The subchannels can be used to transmit other forms of digital data.
Coaxial cable and fiber-optic cable
Microwaves
are electromagnetic waves similar to television signals. In some countries, relay towers spaced about 30 miles (50 kilometers) apart across the country carry programs from the networks to affiliate stations on these waves. Equipment in a tower automatically receives, amplifies, and then retransmits the microwave signal to the next tower. The affiliate stations change the microwave signals back into TV signals.
Satellites
Satellite television systems use direct-broadcast satellites (DBS) to carry signals directly to the homes of subscribers. Such signals are received by dish-shaped antennas. Many older antennas measure about 10 feet (3 meters) across. Some newer home antennas measure only 18 inches (45 centimeters) across.
Receiving television signals
The scanning process used in a TV set rapidly puts the tiny parts of the picture back together piece by piece. The process works so seamlessly that the viewer seems to see only a complete picture. In reproducing the television program, a TV set uses a tuner, amplifiers and separators, and a display device.
Receiving equipment
includes antennas and satellite dishes. A good antenna collects a strong enough television signal for the receiver to produce a picture. The best reception results when the antenna is pointed toward the desired station. Some antennas can be rotated by remote control to align them with widely separated stations.
Cable television signals are transmitted from a station that uses satellite dishes to receive special programming signals from transmission satellites. Satellite dishes for DBS reception are installed so that they aim at a specific point in the sky, from which a satellite in a fixed orbit sends out signals.
Tuner.
Signals from an antenna are fed into the set’s tuner. The tuner selects only the signal from the station the viewer wants to receive, rejecting all others. With most TV sets, the viewer uses a remote control device with buttons that can select channels in any frequency
Most TV sets that receive their signals via cable need a separate cable tuning device commonly called a cable box or set-top box. This device decodes the cable signals and determines which signals to allow. Signals from premium channels are scrambled so they are only available to those who pay the extra subscription price.
Satellite television reception also requires the use of a set-top box. The box decodes the signals received by the satellite dish, and allows access to premium and pay-per-view programming.
The FCC requires television manufacturers to include a digital tuner in every television with a 13-inch (33-centimeter) or larger screen sold in the United States. Earlier analog TV’s without such tuners need a special digital converter box, also called a digital-to-analog converter box, to display digital broadcasts on the TV screen.
Amplifiers and separators.
From the tuner, the television signal goes to electronic circuits in the set. These circuits amplify the signal and separate the audio and video portions of it. The audio signals are changed into sound waves by the speaker. The video signals go to a display device that re-creates the picture for display.
Display devices.
Different kinds of TV sets use different devices to display images. The major types of display devices include cathode-ray tube (CRT) screens, front- and rear-projection systems, and flat panel displays.
Cathode-ray tube screens.
The cathode ray tube, also called the picture tube, was the primary device used for the display of television for many years. CRT TV’s traditionally used analog technology, but newer models use digital technology. The cathode-ray tube transforms video signals into patterns of light that duplicate the scene in front of the camera. One end of the picture tube is rectangular and nearly flat. This end forms the screen of the television set. Inside the set, the picture tube tapers to a narrow neck. The neck of a color picture tube holds three electron guns—one each for the red, blue, and green signals.
Each electron gun in a color picture tube shoots a separate beam of electrons at the screen. Each beam scans the screen just as the beam in each camera tube scanned its target. The screen of a color tube is coated with dots or stripes of red, green, and blue chemicals called phosphors. These chemicals glow with their respective color when struck by an electron beam. The amount of light given off by the phosphors depends on the beam’s strength at the instant it strikes them. Because the beam’s strength is controlled by the video signal from the camera, the phosphors are bright where the scene is bright and dark where the scene is dark.
Front- and rear-projection systems
can use cathode ray tubes or newer technologies to project the television picture onto a screen. Projection television systems are best for people who prefer larger images or want an image that is big enough for a large group of viewers. Large-screen displays are also useful for business applications, such as videoconferencing.
A front-projection system projects a picture from in front of the screen, much like the projector at a movie theater. Front-projection displays produce a lower light output, and so viewing is best in a dark room.
Rear-projection displays are direct-view monitors that can be watched in a variety of lighting conditions. In a rear-projection system, the images are projected onto the back of a screen. Rear-projection sets typically employ mirrors to reflect the image toward the screen.
Flat-panel displays
are used on television sets that can hang on a wall like a picture or can sit on a table as a computer monitor does. Flat-panel systems use a variety of technologies.
One flat-panel system, called plasma display, uses a layer of gas between two glass panels. An electric current passing through the gas ionizes it, producing ultraviolet light that excites red, blue, and green phosphors on the screen.
Another flat-panel system is liquid-crystal display (LCD), which uses molecules called liquid crystals that change how much light they reflect when activated by electric signals. Thousands of tiny transistors on the inner surface of a glass screen control electric signals that activate the liquid crystals.
A field-emission display contains an array of tiny components, each of which works somewhat like a microscopic version of an electron gun in a CRT. The electrons released from the array strike phosphors, producing light. The electrons in a field-emission display travel a much shorter distance than the electrons in a CRT TV.
The development of television technology
Early development.
Many scientists contributed to the development of television, and no one person can be called its inventor. Television became possible in the 1800’s, when people learned how to send communication signals through the air as electromagnetic waves. This process is called radio communication. For details on its development, see Radio (History). 
The first radio operators sent code signals through the air. By the early 1900’s, operators could transmit words. Meanwhile, many scientists had experimented with the transmission of pictures. As early as 1884, Paul Gottlieb Nipkow of Germany had invented a scanning device that sent pictures over short distances. Nipkow’s system worked mechanically, rather than electronically as television does. It used a rotating disk with holes arranged in a spiral around its edge. Light reflected from a scene passed through the holes onto a light-sensitive selenium cell, breaking the image into small pieces.
In 1922, Philo T. Farnsworth of the United States developed an electronic scanning system. In 1925, John Logie Baird, a Scottish engineer, gave the first public demonstration of a mechanical television system. Vladimir K. Zworykin, a Russian-born American scientist, invented the iconoscope and the kinescope in 1923. The iconoscope was the first television camera tube suitable for broadcasting. The kinescope was the picture tube used in TV receivers. Zworykin demonstrated the first completely electronic, practical television system in 1929.
Technological advances
made during the 1950’s and 1960’s helped improve the physical quality of telecasts. At first, most telecasts were live productions or programs made from film. The film took time to develop. Also, the equipment and techniques yielded pictures and sounds of poor quality. Videotaping of programs began in the mid-1950’s and became a major production method. Videotapes can be played back immediately after taping. They produce good quality pictures and sounds, and allow flexibility in program scheduling. Scientists also developed equipment and techniques that improved the quality of filmed shows.
Improvements in broadcasting and receiving equipment have helped provide much clearer television images than in the past. In TV’s early days, all programs were telecast in black and white. Color television broadcasts began in 1953. Today, almost all programs are telecast in color.
A group of nations called the International Telecommunications Satellite Consortium, including the United States, Canada, and Australia, launched the first commercial communications satellite, Early Bird, in 1965. Satellites made worldwide television broadcasting possible. In the 1980’s, satellites gained importance in distributing TV programs to cable systems, broadcasting stations, and home subscribers. Today, viewers can see such events as the Olympic Games as they happen. 
Videocassette recorders (VCR’s) became popular in many industrial countries in the 1980’s. VCR’s recorded visual images and sound on magnetic tape. Many viewers used them to record their favorite shows so they could watch the programs at their leisure. Viewers also could rent pretaped motion pictures and watch them at home. DVR’s later replaced VCR’s for recording programs.
Digital television
represented one of the biggest changes in television since the introduction of color in the 1950’s. In 1993, the International Organization for Standardization (ISO) developed a standard for data compression of the audio and video portions of digital TV signals. The ISO, based in Geneva, Switzerland, tries to establish uniform sizes and other specifications to ease the worldwide exchange of goods and services. The flexibility of the international compression standard allows it to be adapted to different applications. These applications include videoconferencing over telephone networks, desktop video for video-telephone applications, DBS communications, and high-definition television.
In 1996, the FCC adopted a new standard for over-the-air broadcasting of digital television in the United States. This standard delivers about 20 million bits of information per second to a local broadcaster’s coverage area. This capacity can be used to deliver a mixture of video, audio, and data services. Federal government policies in the early 2000’s led to a switch from analog to digital TV broadcasting in the United States. Manufacturers were required to include digital tuners in televisions of a certain size by 2007. All full-power broadcast TV stations were required to broadcast digital rather than analog signals by 2009.
High-definition television
(HDTV) is a type of digital television that produces extremely sharp images. HDTV employs from 720 to more than 1,000 scanning lines, each of which carries a greater amount of detail than an ordinary line. HDTV provides a picture approximately four times as sharp as standard television does. HDTV’s scanning pattern, called progressive scanning, offers greater clarity than interlaced scanning because it scans all the lines at one time in every frame. The screen of an HDTV set is wider in relation to its height than that of a traditional set. Ultra-high-definition television provides a picture much sharper than HDTV.
Limited HDTV transmissions began in Japan in 1989. HDTV began in some parts of Europe in the late 1990’s. Major U.S. broadcasters began broadcasting digital television signals incorporating HDTV in 1998. Australia started HDTV broadcasting in 2002, and New Zealand and South Africa began in 2008.
Television and the internet.
Some of the functions of personal computers can be merged with television technology so that a TV set can be used to browse the internet, send and receive email, and use computer programs called apps. Smart TV sets have such capabilities.
Computers can also be used to watch television programs. People can download and stream programs from the internet to watch them on desktop, laptop, and tablet computers, as well as smartphones. Many young people spend more time watching television on such devices than on TV sets.
Interactive television
is a form of digital television that can give viewers some control over the content of a program and of related information referenced in the program. This capability is especially useful with such applications as video-on-demand, internet browsing, home shopping and banking, and multiplayer electronic games.
Careers in television
The television industry has thousands of job opportunities. It needs such workers as writers, producers, directors, camera operators, engineers, electronics technicians, stagehands, lighting specialists, graphic artists, and set designers to help produce TV shows. Actors and other talent are needed to appear in them. TV news departments provide various jobs for journalists. TV broadcasting also creates many jobs for specialists in accounting and finance, law, management, market research, data analysis, and advertising.
The television industry also employs workers in technical fields outside of broadcasting. Scientists and engineers are needed to design television equipment. Factory workers manufacture television sets and other TV equipment. Technicians service home receivers and install cables, satellite dishes, and TV antennas.
Almost all careers in television require special training. Many colleges and universities have departments that train students in nontechnical broadcasting careers. Journalism schools teach courses in broadcast journalism. Technological institutes and engineering departments of colleges offer training in technical areas of television.
