Three phases of circuit switching network

Circuit switching network implies that there is a dedicated communication path between two stations. That path is a connected sequence of links between network nods. In this circuit switching involves three phases they are given below.

  • Circuit establishment
  • Data transfer
  • Circuit disconnect

Circuit establishment

In this phase the circuit must be established, when signals are transmitted from one station to other station. This can send information through signals before that the receiving end and sending end must establish their circuit.

Data transfer

In this data transfer phase information can be transmitted from one station to other station through network. The data may be analog signals or digital signals that depends on the nature of the network protocol.

Circuit disconnect

After some time of data transfer, the connection is terminated, generally by the action of one of the two stations. Signals must be propagated to given nodes to deallocate the dedicated resources.

Public circuit switching network

A public telecommunications network can be described using four generic architectural components

  • Subscribers
  • Subscriber line
  • Exchanges
  • Trunks


The devices that attach to the network, it is still the case that most subscriber devices to public telecommunications networks are telephones, but the percentage of data traffic increases year by year.

Subscriber line

The link between the subscriber and the network also referred to as the subscriber loop or local loop. Almost all local loop connections use twisted-pair topology. The length of a local loop is typically in a range from a few kilometers to a few tens of kilometers.


The switching centers in the network. A switching center that directly supports subscribers is known as an end office. Typically an end office will support many thousands of subscribers in a localized area.


The branches between exchanges, trunks carry multiple voice frequency circuits using either FDM or Synchronous TDM. Before these were referred to as carrier systems.