The Public Switched Telephone Network (PSTN) offers communications services and infrastructure to the general public. The global circuit-switched telephone networks that are run by national, regional, or local telephony operators collectively make up the PSTN. In order for most telephones to communicate with one another, they include telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables. These are all interconnected via switching centers.
The PSTN, which was once a fixed-line analog telephone network, is now almost all digital in its core network and includes mobile and other networks in addition to fixed telephones.« Glossary Index