Synonymous with PSTS (Public Switched Telephone System). The generic term for the domestic public telephone network, which is traditionally is a public utility providing a circuit-switched network optimized for voice communications. The PSTN comprises all of the telecom infrastructure, including inside plant (ISP) and outside plant (OSP) owned by the carrier or carriers. Customer premises equipment (CPE) and other equipment and facilities owned by end users are considered private and, therefore, not part of the PSTN. As voice increasingly shifts to IP-based networks employing packet switching, and to alternative competitive carriers, such as cable television (CATV) providers, the term PSTN becomes somewhat vague. Global switched telephone network (GSTN) is the generic term for the international public telephone network that comprises the national PSTNs and the facilities that interconnect them. See also CATV, circuit switch, GSTN, IP, ISP, OSP, packet switch, and utility.
(Public Switched Telephone Network) The worldwide voice telephone network. Also called the "plain old telephone system" (POTS) and originally analog only, the heart of most telephone networks today is digital. However, the lines from the home and office to the digital loop carrier (DLC) junction box in the neighborhood typically remain analog. At that point, analog signals are converted to digital. IP Backbones Increasingly, the digital infrastructure of the PSTN is migrating from the TDM-based circuit-switched architecture to IP-based packet switching (see IP telephony). See digital loop carrier and AIN.