Channel (communications) - Examples

Examples

A channel can take many forms. Examples of communications channels include:

1. A connection between initiating and terminating nodes of a circuit.
2. A single path provided by a transmission medium via either
   • physical separation, such as by multipair cable or
   • electrical separation, such as by frequency-division or time-division multiplexing.
3. A path for conveying electrical or electromagnetic signals, usually distinguished from other parallel paths.
   • A storage which can communicate a message over time as well as space
   • The portion of a storage medium, such as a track or band, that is accessible to a given reading or writing station or head.
   • A buffer from which messages can be 'put' and 'got'. See Actor model and process calculi for discussion on the use of channels.
4. In a communications system, the physical or logical link that connects a data source to a data sink.
5. A specific radio frequency, pair or band of frequencies, usually named with a letter, number, or codeword, and often allocated by international agreement.
   Examples:
   • Marine VHF radio uses some 88 channels in the VHF band for two-way FM voice communication. Channel 16, for example, is 156.800 MHz. In the US, seven additional channels, WX1 - WX7, are allocated for weather broadcasts.
   • Television channels such as North American TV Channel 2 = 55.25 MHz, Channel 13 = 211.25 MHz. Each channel is 6 MHz wide. Besides these "physical channels", television also has "virtual channels".
   • Wi-Fi consists of unlicensed channels 1-13 from 2412 MHz to 2484 MHz in 5 MHz steps.
   • The radio channel between an amateur radio repeater and a ham uses two frequencies often 600 kHz (0.6 MHz) apart. For example, a repeater that transmits on 146.94 MHz typically listens for a ham transmitting on 146.34 MHz.
6. A room in the Internet Relay Chat (IRC) network, in which participants can communicate with each other.

All of these communications channels share the property that they transfer information. The information is carried through the channel by a signal.