In telecommunications, a circuit switching network is one that establishes a fixed bandwidth circuit (or channel) between nodes and terminals before the users may communicate, as if the nodes were physically connected with an electrical circuit. The bit delay is constant during the connection, as opposed to packet switching, where packet queues may cause varying delay.
There is a common misunderstanding that circuit switching is used only for connecting voice circuits(Analog or digital).The concept of circuit switching can be extended to other forms of digital data. Dedicated path still remains between two communicating parties and rest of the procedure remains same as voice circuits. But this time around the data is transferred non-stop NOT in the form of packets and without any overhead bits. Although possible, circuit switching is rarely used for transferring digital data (Except voice circuit) and this scheme is not employed in networks where digital data needs to be transferred.
Each circuit 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 that channel remains unavailable to other users. Channels that are available for new calls to be set up are said to be idle.
Virtual circuit switching is a packet switching technology that may emulate circuit switching, in the sense that the connection is established before any packets are transferred, and that packets are delivered in order.
Reference:
http://en.wikipedia.org/wiki/Circuit_switching
