What is a Circuit Switched Network?

A circuit-switched communication system involves three phases: circuit establishment (setting up dedicated links between the source and destination); data transfer (transmitting the data between the source and destination); and circuit disconnect (removing the dedicated links).

The important thing to look for in transmitting information over such a complex network is the path or circuit. In circuit-switching, this path is decided upon before the data transmission starts. The system decides on which route to follow, based on a resource-optimizing algorithm, and transmission goes according to the path. For example, a call from Los Angeles to Chicago will obviously take a different path or circuit than a call from Los Angeles to Miami.

It's important to note the difference between a circuit switched network and a packet switched network. A packet is an internet protocol (IP) that breaks data into chunks and takes those chunks and bundles them into packets. In packet switching, there is no predetermined path.

In modern circuit-switched networks, electronic signals pass through several switches before a connection is established. And during a call, no other network traffic can use those switches. The route for the whole length of the communication session between the two communicating bodies is dedicated, exclusive, and released only when the session terminates.

Circuit-switching is reliable because when you have a circuit dedicated for a session, you are sure to get all information across.