A television station is a set of equipment managed by a business, organisation or other entity, such as an amateur television (ATV) operator, that transmits video content via radio waves directly from a transmitter on the earth's surface to a receiver on earth. Most often the term refers to a station which broadcasts structured content to an audience or it refers to the organization that operates the station. A terrestrial television transmission can occur via analog television signals or, more recently, via digital television signals. Television stations are differentiated from cable television or other video providers in that their content is broadcast via terrestrial radio waves. A group of television stations with common ownership or affiliation are known as a TV network and an individual station within the network is referred to as O&O or affiliate, respectively.