Broadcasting is the distribution of audio and video signals (programs) to a number of recipients ("listeners" or "viewers") that belong to a large group. This group may be the public in general, or a relatively large audience within the public. Thus, an Internet channel may distribute text or music world-wide, while a public address system in (for example) a workplace may broadcast very limited ad hoc soundbites to a small population within its range.
The sequencing of content in a broadcast is called a schedule (broadcasting).
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.
A broadcasting organisation may broadcast several programs at the same time, through several channels (frequencies), for example BBC One and Two. On the other hand, two or more organisations may share a channel and each use it during a fixed part of the day. Digital radio and digital television may also transmit multiplexed programming, with several channels compressed into one ensemble.
When broadcasting is done via the Internet the term webcasting is often used.
A broadcast may be distributed through several physical means. If coming directly from the studio at a single broadcast station, it is simply sent through the airchain to the transmitter. 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.
