A television network is a central organization that distributes its programming to local stations. Usually a network sends its programs via satellite or cable, and programs are aired at the same time nationwide, through what is called the network’s program feed.

The four major broadcasting networks are American Broadcasting Company (ABC), National Broadcasting Company (NBC), Columbia Broadcasting System (CBS) and FOX. All are advertising driven as opposed to the Public Broadcasting System, which is listener, corporate/foundation and government-funded. Of the four major commercial networks, three were originally radio networks. ABC emerged after the FCC broke up the NBC monopoly NBC, owned by David Sarnoff and CBS, run by William Paley, moved onto television in 1948. With them, came the Nielsen Ratings which monitored the viewing habits of the American people.

The three main networks were in fact four when the FCC started to issue television licenses—until 1956 the Dumont Network also existed. Later, in 1986, ABC, NBC and CBS were joined by the FOX Network. Owned by Rupert Murdoch’s News Corporation, FOX now has stations in most of the 211 markets around the country The Big Four in recent years have been joined by two smaller networks, the Warner Brothers Network (the WB, owned by Time Warner) and the United Paramount Network (UPN, owned by Viacom, which owns Nickelodeon and MTV). Stations that are part of the WB or UPN networks are considered independents by many in the industry because only a few hours of broadcasting time originate from the network.

Stations that use network programming generally fall within three categories. First are those called network O&Os, owned and operated by the network. Stations not owned by the network that transmit their signal are called network affiliates; stations can also be part of station groups, which means a chain of stations are owned by an entity other than the network—for example Gannett (newspaper chain) owns a station group.

While networks are vertically integrated (they produce and sell all formats of shows and often own stations), three of the Big Four also form part of larger media conglomerates that are horizontally integrated. ABC is owned by Disney, CBS is owned by Westinghouse/GE and FOX is owned by the News Corporation. Although NBC is owned by NBC Enterprises rather than a conglomerate, it has entered into joint ventures with Microsoft in order to gain a foothold in cable with the news station MSNBC.

Since Ted Turner’s foray into cable, viewership has gone down for network broadcasting. Cable has seen the success of networks owned by Viacom (MTV, Nickelodeon, VH1), USA Broadcasting (Scifi Channel, USA Network), Time Warner (HBO, Showtime, CNN), TCI (Discovery Channel, Court TV) and Cablevision (American Movie Classics, Bravo, Independent Film Channel). The Big Four, in order to maintain dominance, have launched synergistic cable stations such as ESPN, owned by FOX and TCI, or NBC/Microsoft’s MSNBC. Until the opening up of the new format of digital television, viewers can expect to see more joint ventures into the limited marketplace.