Plain old telephone service, the basic analog phone line most folks have in their homes.
Facsimile, a method of sending a copy of a paper document over an analog telephone line.
Modulator/demodulator, a device that connects computer systems or fax machines by transmitting signals using analog signals.
Central office, the phone company’s switching center that provides POTS service to the surrounding area.
Pulse ccde modulation, a way of storing an audio signal as a bit stream.
Code-excited linear prediction, a compression codec used in advanced VoIP codecs. CELP reduces the number of bits necessary for successful transmission of the sound, but it does so by degrading the audio signal somewhat.