Short for plain old telephone system, POTS describes the original telephone system used to make phone calls. This term commonly describes any telephone system designed or installed before the Internet. POTS was widely used in the United States between 1876 and the late 1980s and was an analog signal transmitted over copper lines. As ISDN (Integrated Services Digital Network), cellular phones, and VoIP (Voice over Internet Protocol) became popular, this system stopped being widely used.
Although POTS is old, provides little bandwidth, and is not mobile, it is still more reliable than any other telephony system. Because of this dependability, it's still in use by those needing a dependable solution.