Television broadcaster

A television broadcaster, also known as a television network, is a system for sending television content to multiple stations, pay-TV services, or, in the U.S., multichannel video programming distributors. Before the mid-1980s, most countries had only a few terrestrial networks that dominated programming. Many early networks—like the BBC, CBC, PBS, PTV, NBC, ABC in the U.S., and networks in Australia—grew out of earlier radio networks.

In places where networks send the same centrally produced content to all their stations, and where local transmitters act mainly as repeaters, terms like "television network," "television channel," and "television station" are often used interchangeably in casual conversation, though professionals still distinguish them. In the industry, networks are sometimes ranked based on whether their programming comes from a central point and whether the network’s master control can take over affiliates’ broadcasts in real time, such as during breaking national news.

In North America, many cable and satellite TV services are called "channels" because they differ from traditional networks—they have no local affiliates or component stations, instead reaching viewers directly through cable or satellite providers. These are known as "specialty channels" in Canada or "cable networks" in the U.S.

A network may not produce all its own shows. Production companies like Warner Bros. Television, Universal Television, Sony Pictures Television, and TriStar Television can sell content to various networks, and a single production firm might have programs on rival networks. Networks may also import shows from other countries or use archived programming to fill their schedules.

Some stations can interrupt the network to insert local commercials, station IDs, or emergency alerts. Others break away entirely for their own programming, a practice called regional variation. This is common when smaller networks are part of larger ones. Most commercial TV stations are independently owned, though some are owned and operated by a network. Commercial stations can also be linked to noncommercial educational broadcasters. Some countries have set up national networks so that individual stations act as repeaters for nationwide programs.

Cable TV has changed networks, especially regarding cultural programming. It made possible new channels in major media markets, including programs aimed at bicultural Latino audiences in the U.S., expanding the range of audiences networks and affiliates could target. Media historian Tim P. Vos explained in a 2010 journal article that policymakers did not intend to create a broadcast system dominated by commercial networks; in fact, legislative attempts were made to limit networks’ preferred position.

Modern network operations centers use broadcast automation for most tasks. These systems handle programming and video server playout, using precise atomic time from GPS or other sources to keep perfect synchronization with upstream and downstream systems, making programming appear seamless to viewers.

A major international television broadcaster is the BBC, best known for its news agency BBC News. Owned by the Crown, the BBC funds itself in two ways: UK services branded under BBC are paid for by a television license from British residents, so no advertising appears on them. The advertising-funded arm, BBC Studios, employs 23,000 people worldwide and operates UKTV in the UK. Experimental TV broadcasts began in 1929 using an electromechanical 30-line system by John Logie Baird. Limited regular broadcasts with this system started in 1934, and an expanded service (now called BBC Television) began from Alexandra Palace in November 1936.

Electronic television was demonstrated in San Francisco on September 7, 1927, designed by Philo Taylor Farnsworth, who had been working on it since 1920.

In the United States, TV was long dominated by the Big Three: ABC, CBS, and NBC. Fox, which launched in October 1986, gained prominence and is now considered part of the "Big Four." The Big Three provide many programs to their affiliates, including newscasts, prime time, daytime, and sports programming.