What is another commonly used name for Public Switched Telephone Network (PSTN)?

The term commonly used for the Public Switched Telephone Network (PSTN) is "Plain Old Telephone Service." This phrase reflects the traditional circuit-switched telephone network that has been used for decades to provide voice communications. PSTN encompasses the infrastructure that connects phone calls through a network of circuit-switched lines and switches, enabling basic voice transmission across various geographic areas.

The choice of "Plain Old Telephone Service" emphasizes that this type of service is the foundational technology for telephony, standing in contrast to more modern or advanced communication methods and technologies. It is a straightforward reference to the legacy telephone system that has been widely implemented and understood for years.

This terminology is distinct from the other options, which refer to more advanced or different communication technologies and services. The remaining choices either denote systems related to telecommunications in a broader sense but do not specifically apply to the standard telephony offered by PSTN.