Plain old telephone service

Plain old telephone service (POTS), or rarely publicly offered telephone service, is a retronym for voice-grade telephone service that employs analog signal transmission over copper loops.

POTS was the standard service offering from telephone companies in the United States until c. 1988, when the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) was introduced, followed by the development of cellular telephone systems and voice over internet protocol (VoIP).

Despite the advent of these technologies, POTS remains a basic form of residential and small business connection to the telephone network in many parts of the world. The term encapsulates a technology that has been available since the introduction of the public telephone system in the late 19th century, remaining largely unchanged despite the introduction of innovations such as Touch-Tone dialing, electronic telephone exchanges and fiber-optic communication into the public switched telephone network (PSTN).