Public switched telephone network meaning

The public switched telephone network (PSTN) is the legacy, circuit‑switched public telephone system for fixed‑line voice calls. In practice, it denotes the copper‑based network used to place and receive calls using geographic and non‑geographic numbers, with interconnection between providers, number portability, and access to 999/112. The expression is widely used across telecoms regulation, contracts and compliance documents rather than as a standalone statutory term in current UK law. It featured in earlier EU telecoms instruments and technical standards, and is still used by regulators, including Ofcom (UK) and ComReg (Ireland), in guidance and market materials. Key legal features and significance: - Provides publicly available telephone services (PATS) over a fixed, circuit‑switched infrastructure (including legacy ISDN), distinct from mobile networks and from IP‑based voice (VoIP). - Historically line‑powered, which is relevant to obligations on emergency call access and power‑cut resilience. - Central to interconnection arrangements and migration clauses in telecoms and outsourcing agreements. - Being withdrawn and replaced by all‑IP services; practitioners should address service continuity, device compatibility (alarms, telecare, payment terminals), and regulatory duties during migration. Usage and understanding of PSTN are broadly consistent across England & Wales, Scotland, Northern Ireland and Ireland.