What Is the Public Switched Telephone Network (PSTN)?

The public switched telephone network (PSTN) is the worldwide system of copper wires, fiber optic cables, switching centers and cellular networks that connects phone calls. The PSTN meaning is simple: it is the original phone network, built over more than a century of telecommunications infrastructure. When you pick up a landline phone and dial a number, the call travels through the PSTN.  

The PSTN uses circuit switching, which means a dedicated connection is established between two phones for the duration of a call. This is different from the internet, which uses packet switching to send data in small pieces across shared networks. Circuit switching provides reliable call quality but uses bandwidth less efficiently than modern alternatives. Many contact centers are moving from PSTN-based phone systems to cloud-based platforms that use Voice over Internet Protocol (VoIP). Cloud contact centers like Five9 route calls over the internet, eliminating the need for on-premises PBX hardware and dedicated phone lines. The Five9 Intelligent CX Platform provides enterprise-grade voice quality, geo-redundancy and the flexibility to support agents anywhere with an internet connection.