Public Switched Telephone Network

What is it? 

A public switched telephone network, or PSTN, is a global combination of interconnected voice-oriented public telephone networks. Operating as a conventional circuit-switched telephone network, it encompasses all switched telephone networks run by carriers on local, national, and international levels. 

How does it work? 

PSTNs allow users to make landline calls to each other. This type of network contains switches at centralized points that act as nodes and thus make communication between two points possible. A call gets routed through switches and then finally placed. Consequently, voice signals may travel over the linked phone lines. 

The PSTN phone line is employed together with conventional dial-up network modems. The purpose is to link a computer to the Internet. Such an internet connection may support up to 56 Kbps. 

PSTN architecture 

Typically, PSTN features hierarchical architecture and a star structure. Individual subscriber lines are linked to a local exchange, which interacts with trunk, main, and central exchanges. 

Lines within the limits of the local exchange, as a rule, have the same area code. Therefore, a user who intends to call a number outside the local exchange must add the area code. At the same time, international calls require users to dial the country code.