Public switched telephone network
(also PSTN)
Public switched telephone network definition
The public switched telephone network (frequently shortened to “PSTN”) is the global network of telephone lines for voice and data communications. Despite the rise of newer communication technologies (such as Voice over Internet Protocol or “VoIP”), the PSTN remains the backbone of public telecommunication services and connects a significant portion of the world’s telephone users.
See also: integrated service digital network, VoIP gateway, communications system, signaling gateway, internet telephony, time-division multiplexing, Internet Protocol switching
How the public switched telephone network works
PSTN converts analog voice signals from traditional telephones into digital signals for efficient transmission, then routes them over the network to their destination. To accomplish this, it has a vast infrastructure of interconnected switches, routers, and transmission lines.
In the PSTN, local exchanges handle calls within a specific geographical area (connecting calls between local subscribers), while regional or tandem exchanges manage communication between local exchanges. International exchanges bring the whole system together, facilitating calls between different countries.
PSTN connections use a combination of copper wires, fiber-optic cables, microwave links, and satellite links for connectivity. There is no single set technology for transmitting signals — PSTN can establish connections using multiple techniques (including legacy systems), such as time-division multiplexing (TDM) and Internet Protocol (IP) networking.