Circuit switching

A circuit switched network is one where a dedicated connection (circuit or channel) must be set up between two nodes before they may communicate. For the duration of the communication, that connection may only be used by the same two nodes, and when the communication has ceased, the connection must be explicitly cancelled.

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Early telephone systems are a suitable example. The subscriber would ask the operator to connect them to another subscriber, whether on the same exchange or via an inter-exchange link and another operator. In any case, the end result was a physical electrical connection between the subscriber's telephones for the duration of the call. The copper wire used for the connection could not be used to carry other calls at the same time - even if the subscribers were in fact not talking and the line was silent.

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In later years it became possible to multiplex multiple connections over the same physical conductor, but nonetheless each channel on the multiplexed link was dedicated to one call at a time. Circuit switching can be relatively inefficient because capacity is wasted on connections which are set up but (however momentarily) not in use.

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Circuit switching contrasts with packet switching which splits data (for instance, digital representation of sound, or computer network data) into chunks which are separately routed over a shared network.

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In telecommunication, the term circuit switching has the following meanings:

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1. A method of routing traffic between an originator and a destination through switching centers, from local users or from other switching centers, whereby a continuous electrical circuit is established and maintained between the calling and called stations until it is released by one of those stations.

Related Topics:
Routing - Traffic - Switching center - Circuit

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The method of establishing the connection and monitoring its progress and availability may utilize a separate control channel as in the case of ISDN or not as in the case of the Public Switched Telephone Network.

Related Topics:
ISDN - Public Switched Telephone Network

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2. A process that, on demand, connects two or more data terminal equipments (DTEs) and permits the exclusive use of a data circuit between them until the connection is released. The acronym CSD (Circuit Switched Data) is also used, as in GSM's original data transfer method HSCSD.

Related Topics:
Data - Terminal - DTE - Circuit - Circuit Switched Data - GSM - HSCSD

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