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The public switched telephone network (PSTN) refers to the international telephone system that uses copper wires to carry analog voice data. It consists of a collection of individual telephones that are hardwired to a public exchange.
The public switched telephone network was formerly known simply as the public telephone network.
The public switched telephone network is a global system that has developed over several decades. From the early research of Alexander Graham Bell, telecommunications companies evolved the PSTN architecture that provided for yesterday's landline voice communications.
One important distinction with the public switched telephone network is that it stands in contrast to private exchange networks. Private branch exchanges and other technologies allowed companies and other parties to create more individual telephone lines that were not represented in the PSTN and public landline architecture. One way to explain this is that individual lines were built into private endpoint systems, so that an individual recipient could have many different individual phone lines using the same public switched telephone network trajectory.
Today, as smartphones and mobile devices continue to proliferate, wireless telecom networks are taking up market share and PSTN landline technology is diminishing. In some places, less industrialized communities have skipped directly from an underserved or insufficient public switched telephone network architecture directly to the use of cell phones and mobile devices.
PSTN has also been known to stand for "pretty standard telephone network," a tongue-in-check expression referring to its slow speed.