In telecommunications, a circuit switching network is one that establishes a dedicated circuit (or channel) between nodes and terminals before the users may communicate. Each circuit that is dedicated cannot be used by other callers until the circuit is released and a new connection is set up. Even if no actual communication is taking place in a dedicated circuit then, that channel still remains unavailable to other users. Channels that are available for new calls to be set up are said to be idle. Copy of the original phone of Graham Bell at the Musée des Arts et Métiers in Paris Telecommunication is the transmission of signals over a distance for the purpose of communication. ... A telecommunication circuit is defined as follows: The complete path between two terminals over which one-way or two-way communications may be provided. ... Channel, in communications (sometimes called communications channel), refers to the medium used to convey information from a sender (or transmitter) to a receiver. ... A node is a device that is connected as part of a computer network. ... In the context of telecommunications, a terminal is a device which is capable of communicating over a line. ...

For call setup and control (and other administrative purposes), it is possible to use a separate dedicated signalling channel from the end node to the network. ISDN is one such service that uses a separate signalling channel while Plain Old Telephone Service (POTS) does not. In telecommunication, signalling (or signaling) has the following meanings: The use of signals for controlling communications. ... ISDN is also short for isosorbide dinitrate Integrated Services Digital Network (ISDN) is a type of circuit switched telephone network system, designed to allow digital (as opposed to analog) transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher speeds, than available with analog... Plain old telephone service, or POTS, are the services available from analogue telephones prior to the introduction of electronic telephone exchanges into the public switched telephone network. ...

The method of establishing the connection and monitoring its progress and termination through the network may also utilize a separate control channel as in the case of links between telephone exchanges which use CCS7 to communicate the call setup and control information and use TDM to transport the actual circuit data. Signalling System #7 (SS7) is a set of telephony signalling protocols which are used to set up the vast majority of the worlds PSTN telephone calls. ... Time-division multiplexing (TDM) is a type of digital or (rarely) analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but physically are taking turns on the channel. ...

Early telephone systems are a suitable example of circuit switching. 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 two subscribers' 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.

In later years it became possible to multiplex multiple connections over the same physical conductor, but nonetheless each channel on the multiplexed link was either dedicated to one call at a time, or it was idle between calls. Circuit switching can be relatively inefficient because capacity is wasted on connections which are set up but are not in continuous use (however momentarily). On the other hand, the connection is immediately available and capacity is guaranteed until the call is disconnected. In telecommunications, multiplexing (also muxing or MUXing) is the combining of two or more information channels onto a common transmission medium using hardware called a multiplexer or (MUX). ...

Circuit switching contrasts with packet switching which splits traffic data (for instance, digital representation of sound, or computer data) into chunks, called packets, that are routed over a shared network. Packet switching networks do not require a circuit to be established and allow many pairs of nodes to communicate almost simultaneously over the same channel. Each packet is individually addressed precluding the need for a dedicated path to help the packet find its way to its destination. In computer networking and telecommunications, packet switching is a communications paradigm in which packets (messages or fragments of messages) are individually routed between nodes, with no previously established communication path. ... In computer networking and telecommunications, packet switching is a communications paradigm in which packets (messages or fragments of messages) are individually routed between nodes, with no previously established communication path. ...

See also

• Packet switching
• Message switching

In computer networking and telecommunications, packet switching is a communications paradigm in which packets (messages or fragments of messages) are individually routed between nodes, with no previously established communication path. ... In telecommunications, message switching was the precursor of packet switching, where messages were routed in their entirety, one hop at a time. ...

External links

• Netheads vs Bellheads by Steve Steinberg
• Out of Sight, Out of Mind, Big Old Stupid Telephone Companies Are Throwing Away Their Only Real Asset Opinion piece on packet switching vs circuit switching