There are two types of radio network currently in use around the world: the one-to-many (
simplex communication
Simplex communication is a communication channel that sends information in one direction only."Simplex" ''The IEEE Authoritative Dictionary of Standard Terms, 7th Ed.'', 2000, Inst. of Electrical and Electronic Engineers, p.1053
The Internationa ...
)
broadcast network
A terrestrial network (or broadcast network in the United States) is a group of radio stations, television stations, or other electronic media outlets, that form an agreement to air, or broadcast, content from a centralized source. For example, ...
commonly used for public information and
mass-media
Mass media refers to a diverse array of media technologies that reach a large audience via mass communication. The technologies through which this communication takes place include a variety of outlets.
Broadcast media transmit information e ...
entertainment, and the
two-way radio
A two-way radio is a radio that can both transmit and receive radio waves (a transceiver), unlike a broadcast receiver which only receives content. It is an audio (sound) transceiver, a transmitter and receiver in one unit, used for bidirecti ...
(
duplex communication) type used more commonly for public safety and public services such as
police
The police are a constituted body of persons empowered by a state, with the aim to enforce the law, to ensure the safety, health and possessions of citizens, and to prevent crime and civil disorder. Their lawful powers include arrest and th ...
, fire,
taxicabs
A taxi, also known as a taxicab or simply a cab, is a type of vehicle for hire with a driver, used by a single passenger or small group of passengers, often for a non-shared ride. A taxicab conveys passengers between locations of their choice ...
, and delivery services. Cell phones are able to send and receive simultaneously by using two different frequencies at the same time. Many of the same components and much of the same basic technology applies to all three.
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 (
transmitter
In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...
s) with co-located receivers and mobile receivers/transmitters or
transceiver
In radio communication, a transceiver is an electronic device which is a combination of a radio ''trans''mitter and a re''ceiver'', hence the name. It can both transmit and receive radio waves using an antenna, for communication purposes. Thes ...
s. 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 microwave 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
In telecommunications, trunking is a technology for providing network access to multiple clients simultaneously by sharing a set of circuits, carriers, channels, or frequencies, instead of providing individual circuits or channels for each cli ...
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
A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link while ...
systems where each fixed and mobile radio is specifically identified to the system controller and its operation is switched by the controller.
Broadcasting networks
The broadcast type of radio network is a network system which distributes
programming to multiple
stations simultaneously, or slightly delayed, for the purpose of extending total coverage beyond the limits of a single broadcast signal. The resulting expanded audience for radio programming or information essentially applies the benefits of
mass-production
Mass production, also known as flow production or continuous production, is the production of substantial amounts of standardized products in a constant flow, including and especially on assembly lines. Together with job production and bat ...
to the
broadcasting
Broadcasting is the distribution of audio or video content 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 beg ...
enterprise. A radio network has two sales departments, one to package and sell programs to radio stations, and one to sell the audience of those programs to advertisers.
Most radio networks also produce much of their programming. Originally, radio networks owned some or all of the stations that broadcast the network's
radio format
A radio format or programming format (not to be confused with broadcast programming) describes the overall content broadcast on a radio station. The radio format emerged mainly in the United States in the 1950s, at a time when radio was compelle ...
programming. Presently however, there are many networks that do not own any stations and only produce and/or distribute programming. Similarly station ownership does not always indicate network affiliation. A company might own stations in several different markets and purchase programming from a variety of networks.
Radio networks rose rapidly with the growth of regular broadcasting of radio to home listeners in the 1920s. This growth took various paths in different places. In
Britain
Britain most often refers to:
* The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands
* Great Britain, the largest island in the United King ...
the
BBC #REDIRECT BBC #REDIRECT BBC
Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...
...
in its early decades. In contrast, in the
revenue. In that instance, the same corporation that owned or operated the network often manufactured and marketed the listener's radio.
Major technical challenges to be overcome when distributing programs over long distances are maintaining signal quality and managing the number of switching/relay points in the
. Early on, programs were sent to remote stations (either owned or affiliated) by various methods, including leased
s and audio tape. The world's first all-radio, non-wireline network was claimed to be the
that began operation in June 1948. Terrestrial
relay, a technology later introduced to link stations, has been largely supplanted by
, which usually offer superior cost-benefit ratios.
Many early radio networks evolved into
s.