Public Switched Telephone Network (PSTN)

The PSTN is the world’s collection of interconnected voice-oriented public telephone networks, both commercial and government owned. The network is operated by national, regional, or local telephone operators. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all interconnected by switching centers, thus allowing most telephones to communicate with each other. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core network and includes mobile and other networks, as well as fixed telephones.