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In communications, such as radio and television, broadcasting means sending information such as television shows or music electronically to a large audience. The information is sent through the air in radio waves, through a wire, or by a communications satellite, and then the television viewers or radio listeners pick up the signal using their television sets and radio receivers. Gugliemo Marconi invented wireless telegraphy, in December 1901 he transmitted first radio signals across the Atlantic Ocean. This was point to point. Experiments with voice broadcasting began a few years later, and it grew rapidly in the 1920s.
Types of broadcasters
Different broadcasters use different radio waves and different modulating methods. amplitude modulation on medium waves was the first to be much used.
In the United States, most public broadcast radio and television stations are run by educational groups (such as colleges or universities) or by a state's educational department. Public broadcasters, by law, cannot accept or display commercial advertising. However, businesses can make donations to a public broadcaster. Most are part of the Public Broadcasting System.
PBS is different than the other public broadcasters such as BBC, NHK and CBC, because the PBS gets a lot of its funding (money) from donations by viewers and listeners. Public broadcasters make programs that the private companies are not interested in making, such as educational children's shows, documentaries, and public affairs shows about current issues.
As well, there are private broadcasting companies. These are companies that broadcast television and radio programs. To make money, private broadcasting companies sell advertisements called commercials.
A third type of broadcaster is community broadcasters. There are community television stations and community radio stations.
Community television stations are often provided on cable networks. Community television stations usually have shows about local issues and community events. Some community television stations film and broadcast community cultural activities, such as musical performances or town hall meetings.
Community radio stations play music and have public affairs shows about community issues. Community radio stations are usually small organizations that are run by volunteers. Community radio stations often get their funding (money) from local governments, local universities, and from donations by listeners. Some community radio stations also have poetry readings by local poets, or performances by local musicians or singers.
Broadcasting can also mean sending a message to many users on a computer network at exactly the same time, or sending a message from one computer to many other computers, giving information about itself, such as its name and location.
Sending information to a small selected group is called narrowcasting.el:Ραδιοφωνία