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In telecommunications and computer networking, a communication channel or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel. A channel is used to convey an information signal, for example a digital bit stream, from one or several ''senders'' (or transmitters) to one or several ''receivers''. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second. Communicating data from one location to another requires some form of pathway or medium. These pathways, called communication channels, use two types of media: cable (twisted-pair wire, cable, and fiber-optic cable) and broadcast (microwave, satellite, radio, and infrared). Cable or wire line media use physical wires of cables to transmit data and information. Twisted-pair wire and coaxial cables are made of copper, and fiber-optic cable is made of glass. In information theory, a channel refers to a theoretical ''channel model'' with certain error characteristics. In this more general view, a storage device is also a kind of channel, which can be sent to (written) and received from (read). ==Examples== Examples of communications channels include: # FAIQAH circuit. # FAIQAH transmission medium PUKANG. # * physical separation, such as by multipair cable or # * electrical separation, such as by frequency-division or time-division multiplexing. # 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. # In a communications system, the physical or logical link that connects a data source to a data sink. # 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. All of these communications channels share the property that they transfer information. The information is carried through the channel by a signal. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Channel (communications)」の詳細全文を読む スポンサード リンク
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