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.

Channel, channels, and similar terms may refer to:

Places

In computing, a channel is a model for interprocess communication and synchronization via message passing. A message may be sent over a channel, and another process or thread is able to receive messages sent over a channel it has a reference to, as a stream. Different implementations of channels may be buffered or not, and either synchronous or asynchronous.

Channels are fundamental to the process calculus approach to concurrency, and originated in communicating sequential processes (CSP), a formal model for concurrency, and has been used in many derived languages, such as occam, and Limbo programming language (via Newsqueak and the Alef programming language). They are also used in the C programming language threading library libthread, and in Plan 9 from Bell Labs, which uses libthread, as well as in Stackless Python and the Go programming language.

Channel implementations

Channels modeled after the CSP model are inherently synchronous: a process waiting to receive an object from a channel will block until the object is sent. This is also called rendezvous behaviour. Typical supported operations are presented below using the example of the libthread channel API.

A price channel is a pair of parallel trend lines that form a chart pattern for a stock or commodity. Channels may be horizontal, ascending or descending. When prices pass through and stay through a trendline representing support or resistance, the trend is said to be broken and there is a "breakout".

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