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.

Forms of electronic broadcasting

Historically, there have been several different types of electronic broadcasting mediums:

• Telephone broadcasting (1890–1932): the earliest form of electronic broadcasting, not counting the data services offered by stock telegraph companies from 1867, if ticker-tape machines are excluded from broadcasting's popular definition. Telephone broadcasting began with the advent of telephone newspaper services for news and entertainment programming which were introduced in the 1890s and primarily located in large European cities. These telephone-based systems were the first example of electronic broadcasting and offered a wide variety of programming.
• Radio broadcasting (experimentally from 1906, commercially from 1920): radio broadcasting is an audio (sound) broadcasting service, broadcast through the air as radio waves from a transmitter to an antenna and, thus, to a receiving device. Stations can be linked in radio networks to broadcast common programming, either in syndication or simulcast or both.
• Television broadcasting (experimentally from 1925, commercially from the 1930s): this video-programming medium was long-awaited by the general public and rapidly rose to compete with its older radio-broadcasting sibling.
• Cable radio (also called "cable FM", from 1928) and cable television (from 1932): both via coaxial cable, serving principally as transmission mediums for programming produced at either radio or television stations, with limited production of cable-dedicated programming.
• Satellite television (from circa 1974) and satellite radio (from circa 1990): meant for direct-to-home broadcast programming (as opposed to studio network uplinks and downlinks), provides a mix of traditional radio and/or television broadcast programming with satellite-dedicated programming.
• Webcasting of video/television (from circa 1993) and audio/radio (from circa 1994) streams: offers a mix of traditional radio and television station broadcast programming with internet-dedicated webcast programming.

http://en.wikipedia.org/wiki/Broadcasting