--- remote stations (either owned or affiliated) by various methods, including leased telephone lines, pre-recorded gramophone records and audio tape.
The world's first all-radio, non-wire line network was claimed to be the Rural Radio Network, a group of six upstate New York FM stations that began operation in June 1948. Terrestrial microwave relay, a technology later introduced to link stations, has been largely supplanted by coaxial cable, fiber, and satellite, which usually offer superior cost-benefit ratios.
Many early radio networks evolved into Television networks.
Radio network
The Two-way type of radio network shares many of the same technologies and components as the Broadcast type radio network but is generally set up with fixed broadcast points (transmitters) with co-located receivers and mobile receivers/transmitters or Transceivers. In this way both the fixed and mobile radio units can communicate with each other over broad geographic regions ranging in size from small single cities to entire states/provinces or countries. There are many ways in which multiple fixed transmit/receive sites can be interconnected to achieve the range of coverage required by the jurisdiction or authority implementing the system:
conventional wireless links in numerous frequency bands, fibre-optic links, or micro-wave links. In all of these cases the signals are typically backhauled to a central switch of some type where the radio message is processed and resent (repeated) to all transmitter sites where it is required to be heard.
In contemporary two-way radio systems a concept called trunking is commonly used to achieve better efficiency of radio spectrum use and provide very wide ranging coverage with no switching of channels required by the mobile radio user as it roams throughout the system coverage.
Trunking of two-way radio is identical to the concept used for cellular phone systems where each fixed and mobile radio is specifically identified to the system Controller and its operation is switched by the controller. See also the entries Two-way radio and Trunked radio system to see more detail on how various types of radios and radio systems work.
Television network
A television network is a distribution network for television content whereby a central operation provides programming for many television stations. Until the mid-1980s, television programming in most countries of
---early television networks (e.g. the BBC, NBC or CBS) evolved from earlier radio networks.
In countries where most networks broadcast identical, centrally originated content to all their stations and where most individual transmitters therefore operate only as large "repeater stations", the terms television network, television channel and television station have become interchangeable in everyday language, with only professionals in TV-related occupations continuing to make a difference between them. Within the industry, a tiering is sometimes created among groups of networks based on whether their programming is simultaneously originated from a central point, and whether the network master control has the technical and administrative capability to take over the programming of their affiliates in real-time when it deems this necessary—the most common example being breaking national news events.
In North America in particular, many television channels available via cable and satellite television are branded as "networks" but are not truly networks in the sense defined above, as they are singular operations – they have no affiliates or component stations. Such channels are more precisely referred to by terms such as "specialty channels" (Canada) or "cable networks" (U.S.), although the latter term is somewhat of a misnomer, even though these channels are networked across the country by various cable and satellite systems.
A network may or may not produce all of its own programming. If not, production houses such as Warner Bros. and Sony Pictures can distribute their content to the different networks and it is common that a certain production house may have programmes on two or more rival networks.
Similarly, some networks may import television programmes from other countries or use archival programming to help complement their schedules.
Regulation
FCC regulations in the United States restricted the number of television stations that could be owned by any one network, company or individual.
This led to a system where most local television stations were independently owned, but received programming from the network through a franchising contract, except in a few big cities that had network owned-and-operated stations and independent stations. In the early days of television, when there were often only one or two stations broadcasting in an area, the stations were usually affiliated with several networks and were
--- able to choose which programs to air. Eventually, as more stations were licensed, it became common for each station to be affiliated with only one network and carry all of the "prime time" network programs. Local stations however occasionally break from regularly scheduled network programming, especially when there is breaking local news (e.g. severe weather). Moreover, when stations return to network programming from commercial breaks, the station's logo is displayed in the first few seconds before switching to the network's logo.
Another FCC regulation, the Prime Time Access Rule, restricted the number of hours of network programming that could be broadcast on the local affiliate stations. This was done to encourage the development of locally produced programs and to give local residents access to broadcast time.
More often, the result included a substantial amount of syndicated programming, usually consisting of old movies, independently produced and syndicated shows, and reruns of network programs. Occasionally, these shows were presented by a local host, especially in programs that showed cartoons and short comedies intended for children. See List of local children's television series (United States).