The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session.
Even if no actual communication is taking place, the channel remains reserved and protected from competing users.
The advantage of using circuit switching is that it provides for continuous transfer without the overhead associated with packets, making maximal use of available bandwidth for that communication.
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.
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 packet-switched signalling protocol to communicate the call setup and control information and use TDM to transport the actual circuit data.
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.
As a result, datagram packet switching networks do not require a circuit to be established and allow many pairs of nodes to communicate concurrently over the same channel.