Broadcasting is the distribution of audio and/or video signals which transmit programs to an audience. The audience may be the general public or a relatively large sub-audience, such as children or young adults.
There are wide variety of broadcasting systems, all of which have different capabilities. The largest broadcasting systems are institutional public address systems, which transmit nonverbal messages and music within a school or hospital, and low-powered broadcasting systems which transmit radio stations or television stations to a small area. National radio and television broadcasters have nationwide coverage, using retransmitter towers, satellite systems, and cable distribution. Satellite radio and television broadcasters can cover even wider areas, such as entire continents, and Internet channels can distribute text or streamed music worldwide.
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" was coined by early radio engineers from the midwestern United States. 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:
- in-kind donations of time and skills by volunteers (common with community broadcasters)
- direct government payments or operation of public broadcasters
- indirect government payments, such as radio and television licenses
- grants from foundations or business entities
- selling advertising or sponsorships
- public subscription or membership
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.
Recorded broadcasts and live broadcasts
One can record and 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 this is referred to as "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, and now mostly by satellite.
Distribution to stations or networks may also be through physical media, such as analogue 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.
Since 1956, sound and television broadcasts were included as copyright works. Copyright, Designs and Patents Act 1988 defines a broadcast as a transmission by wireless telegraphy of visual images, sounds, or other information which is capable of lawful reception by the public or which is made for presentation to the public. It thus covers radio, television, teletext et al.