PSTN (Public Switched Telephone Network)
The global network of copper-wire and fiber circuits that carries traditional analog and digital telephone calls.
The Public Switched Telephone Network (PSTN) is the aggregate of the world's circuit-switched telephone networks — the infrastructure of copper wires, fiber optic cables, microwave links, cellular towers, and switching centers that has powered voice communication since the late 19th century. When you dial a phone number, the PSTN routes the call through a series of switches to connect your line with the destination.
VoIP systems must interconnect with the PSTN to call or receive calls from traditional landlines and mobile phones. This connection is made through SIP trunks or via the carrier's VoIP gateway. As businesses migrate to cloud communications, the PSTN is being gradually phased out — the FCC has authorized carriers to retire legacy copper infrastructure, and many countries have set deadlines for PSTN decommissioning.
For businesses, PSTN connectivity is handled transparently by their VoIP or Cloud PBX provider. Zonitel maintains direct interconnects with major PSTN carriers across North America, ensuring that calls to and from any phone number — landline, mobile, or VoIP — connect reliably without the business needing to manage carrier relationships directly.