is the distribution of audio and/or video content or other messages to a dispersed audience
via any electronic mass communications
medium, but typically one using the electromagnetic spectrum
(radio waves), in a one-to-many model. Broadcasting began with AM radio, which came into popular use around 1920 with the spread of vacuum tube radio transmitters and receivers. Before this, all forms of electronic communication (early radio, telephone
, and telegraph) were one-to-one, with the message intended for a single recipient
. The term broadcasting
, borrowed from the agricultural method of sowing seeds in a field by casting them broadly about, was coined by either KDKA manager Frank Conrad or RCA historian George Clark around 1920 to distinguish this new activity of "one-to-many" communication; a single radio station transmitting to multiple listeners.
Over the air broadcasting is usually associated with radio and television, though in recent years both radio and television transmissions have begun to be distributed by cable
(cable television). The receiving parties may include the general public or a relatively small subset; the point is that anyone with the appropriate receiving technology and equipment (e.g., a radio or television set) can receive the signal. The field of broadcasting includes both government-managed services such as public radio, community radio and public television, and private commercial radio and commercial television. The U.S. Code of Federal Regulations
, title 47, part 97 defines "broadcasting" as "transmissions intended for reception
by the general public, either direct or relayed". Private or two-way telecommunications transmissions do not qualify
under this definition. For example, amateur ("ham") and citizens band
(CB) radio operators are not allowed to broadcast. As defined, "transmitting" and "broadcasting" are not
of radio and television programs from a radio or television station to home receivers by radio waves is referred to as "over the air" (OTA) or terrestrial broadcasting and in most countries requires a broadcasting license. Transmissions using a wire
or cable, like cable television (which also retransmits OTA stations with their consent), are also considered broadcasts, but do not necessarily require a license (though in some countries, a license is required). In the 2000s, transmissions of television and radio programs via streaming digital technology have increasingly been referred to as broadcasting as well, though strictly speaking this is incorrect.