Strictly speaking, there is no such thing as a cable "network", but it is easy to understand how the term came to be used for national cable channels.
Networks predate cable. In fact, networks predate television. Networks arise from the fact that radio signals have a limited reach. The typical AM radio station has a broadcast radius of about 100 miles within which its signal can be received clearly. So a radio show being broadcast live in New York cannot be heard in Philadelphia or Washington, D.C. via direct broadcast. The desire to carry live broadcasts of news and sporting events inspired radio stations across the country to band together in "networks" which could share such programming. Initially carried by telephone wires, later by dedicated cables, the networks linked radio stations in different cities and allowed all of them to take the signal from the cable and then rebroadcast it over the air to their own local audience.
The major radio companies soon came to own a great many stations, and to share their programs with "affiliates" - independently owned stations that also carried network programs. The Columbia Broadcasting System (CBS) was one of the three major networks. The other two were both owned by the National Broadcasting Company - which in turn was owned by the Radio Corporation of America, maker of radio receivers. Each covered different cities and they were known as the Red and the Blue networks.
For dramas and comedies essentially the same system was used, except that some stations (especially on the west coast) would record the signal off the cable feed onto wire or wax disc when it was transmitted (usually from New York) and play it back later. So the same show could air at 7 PM in New York and Los Angeles. You have to remember that the continental United States covers four time zones, so delivering TV (and radio) signals to the entire country is a much bigger problem than it is in the U.K. where distances are comparatively modest. (Counting Alaska, Hawaii and territories the U.S. covers eight time zones.)
When television came in the whole radio system, including ratings and advertising support, was transplanted to the new medium. A federal court anti-trust ruling forced NBC to give up either its red or blue network - I forget which. That spin-off network became the American Broadcasting Company (ABC), the third of the original "three major" networks. (Early television manufacturer DuMont had a network of five stations in five major east coast cities, but both the network and the TV factory soon went bust. I'm old enough that my family owned a DuMont television - our first - but not old enough to have watched any shows on the DuMont network. It had already vanished by the time I was born. /forums/images/graemlins/smile.gif)
The three broadcast networks, CBS, NBC and ABC, dominated American televison for the better part of 30 years. The Public Broadcasting System, a partially state-funded "network" of educational television stations which did not accept advertising, was founded in the mid 1960s, but was never real competition for the "Big Three" in terms of audience, and obviously wasn't any competition at all in terms of advertising dollars. Despite several attempts, no one would put together a viable fourth network until 1987, when Fox debuted, and it would not begin to attract a large audience for several years after that. In those days the broadcast networks routinely attracted audiences of 50 and 60 million people for individual shows, since nearly every American home received them, cable was niche system used to carry broadcast signals to remote rural areas and to watch uncut Hollywood movies in a handful of major cities. Satellite was almost unknown, and was delivered by 10 to 20 foot dishes, again mostly in rural areas. Most satellite broadcasts were not aimed at viewers with ground-stations, they were merely intercepting network signals being beamed to affiliates across the country.
Because cable channels like Sci-Fi and TNT are available nationwide, they are referred to as "networks", even though there are no local stations that are picking up and broadcasting their signals. The closest thing they have to "affiliates" are local cable companies which can choose to carry their signals (or not) and direct satellite providers like Dish Network and DirecTV.
Regards,
Joe
