Experiments in broadcasting television began in the 1920s but were interrupted by World War II. In 1996 there were 1,340 commercial television stations on the air, and 600 noncommercial stations. There were also more than 2,000 low-power television stations. The Corporation for Public Broadcasting was established in 1968 as a not-for-profit, nongovernmental agency to finance the growth of noncommercial radio and television; by 2003 the network served more than 200 television and nearly 800 radio stations.
New and competing technologies have had a tremendous impact on broadcasting and the ways in which people use it. With the availability of small, high-quality portable and automotive receivers, it has been estimated that less than half of all radio listening takes place in the home. Cable television, which reached more than 67% of all U.S. homes by 2003, gave consumers a wider choice of programs from which to choose. The new cable channels, most of them highly specialized in the programming they offer, coupled with the wide availability of videocassettes and DVDs, have reduced the influence of the broadcast networks. Television signals are also now transmitted from satellites direct to household satellite dishes.
See E. Barnouw, A History of Broadcasting in the United States (3 vol., 1966-70); J. R. Bittner, Broadcasting and Telecommunication: An Introduction (1985); S. J. Douglas, Inventing American Broadcasting, 1899-1922 (1997); J. R. Walker and D. A. Ferguson, The Broadcast Television Industry (1998).
There is a wide variety of broadcasting systems, all of which have different capabilities. The smallest broadcasting systems are institutional public address systems, which transmit spoken messages and music within, for example, a school or hospital, and low-powered radio or television stations transmitting programs to a small local area. National radio and television broadcasters have nationwide coverage, using retransmitter towers, satellite systems, and cable distribution. Satellite radio and television broadcasting can cover areas as wide as entire continents, while internet channels can distribute text or streamed music and speech worldwide. Individuals can also use make use of internet services to stream or podcast sound or video.
The sequencing of content in a broadcast is called a schedule. As with all technological endeavors, a number of technical terms and slang have developed. A list of these terms can be found at list of broadcasting terms. Television and radio programs are distributed through radio broadcasting or cable, often both simultaneously. By coding signals and having decoding equipment in homes, the latter also enables subscription-based channels and pay-per-view services.
The term "broadcast" originally referred to the sowing of seeds by scattering them over a wide field. It was adopted by early radio engineers from the midwestern United States to refer to the analogous dissemenation of radio signals. Broadcasting forms a very large segment of the mass media. Broadcasting to a very narrow range of audience is called narrowcasting.
Economically there are a few ways in which stations are able to continually broadcast. Each differs in the method by which stations are funded:
Broadcasters may rely on a combination of these business models. For example, National Public Radio, a non-commercial network within the United States, receives grants from the Corporation for Public Broadcasting (which in turn receives funding from the U.S. government), by public membership, and by selling "extended credits" to corporations.
The first regular television broadcasts began in 1937. One can record and produce live broadcasts. The former allows correcting errors, and removing superfluous or undesired material, rearranging it, applying slow-motion and repetitions, and other techniques to enhance the program. However some live events like sports telecasts can include some of the aspects including slow motion clips of important goals/hits etc in between the live telecast.
American radio network broadcasters habitually forbade prerecorded broadcasts in the 1930s and 1940s requiring radio programs played for the Eastern and Central time zones to be repeated three hours later for the Pacific time zone. This restriction was dropped for special occasions, as in the case of the German dirigible airship Hindenburg at Lakehurst, New Jersey in 1937. During World War II, prerecorded broadcasts from war correspondents were allowed on U.S. radio. In addition, American radio programs were recorded for playback by Armed Forces Radio stations around the world.
A disadvantage of recording first is that the public may know the outcome of an event from another source, which may be a spoiler. In addition, prerecording prevents live announcers from deviating from an officially-approved script, as occurred with propaganda broadcasts from Germany in the 1940s and with Radio Moscow in the 1980s.
Many events are advertised as being live, although they are often "recorded live" (sometimes called "live-to-tape"). This is particularly true of performances of musical artists on radio when they visit for an in-studio concert performance. This intentional blurring of the distinction between live and recorded media is viewed with chagrin among many music lovers. Similar situations have sometimes appeared in television ("The Cosby Show is recorded in front of a live studio audience").
A broadcast may be distributed through several physical means. If coming directly from the studio at a single radio or tv station, it is simply sent through the air chain to the transmitter and thence from the antenna on the tower out to the world. Programming may also come through a communications satellite, played either live or recorded for later transmission. Networks of stations may simulcast the same programming at the same time, originally via microwave link, now usually by satellite.
Distribution to stations or networks may also be through physical media, such as analog or digital videotape, CD, DVD, and sometimes other formats. Usually these are included in another broadcast, such as when electronic news gathering returns a story to the station for inclusion on a news programme.
The final leg of broadcast distribution is how the signal gets to the listener or viewer. It may come over the air as with a radio station or TV station to an antenna and receiver, or may come through cable TV or cable radio (or "wireless cable") via the station or directly from a network. The Internet may also bring either radio or TV to the recipient, especially with multicasting allowing the signal and bandwidth to be shared.
The term "broadcast network" is often used to distinguish networks that broadcast an over-the-air television signal that can be received using a television antenna from so-called networks that are broadcast only via cable or satellite television. The term "broadcast television" can refer to the programming of such networks. '''