PSTN (Public Switched Telephone Network)

This is the most commonly used method by all users that only have the need to use one line for one conversation at a time using only one phone number. PSTN uses an old technology whereby circuit-switched copper phone lines are used to transmit analogue voice data. It is the basic service that you have at home and in a small business. As a dedicated service, a PSTN line cannot be used for any other purpose while a call is being made.