broadcasting, transmission of sound or images to a large number of receivers by radio or television. In the United States the first regularly scheduled radio broadcasts began in 1920 at 8XK (later KDKA) in Pittsburgh. The sale of advertising was started in 1922, establishing commercial broadcasting as an industry. Radio became increasingly attractive as an advertising medium with the coming of network operation. A coast-to-coast hookup was tentatively effected early in 1924, and expansion of both audience and transmission facilities continued rapidly. By 1927 there were two major networks, and the number of stations had so increased that interference became a serious problem. Legislation (see Federal Communications Commission) designed to meet this problem was enacted, and the government has since maintained some control over the technical and business activities of the industry. By 2003, 4,804 commercial radio stations were operating in the original AM (amplitude modulation) broadcast band. Commercial broadcasting on the FM (frequency modulation) band began in 1941. The number of FM stations passed the number of AM in 1983; in 1998 there were 6,179 commercial FM stations on the air, and 2,400 noncommercial stations.

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 radio; television.