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1.
Public Switched Telephone Network

PSTN is the oldest, slowest, and most common phone connection based on twisted-pair copper wires carrying analog data. This technology uses RJ-ll connectors. Computers require modems to convert digital signals from the computer to the anlog waveforms that travel across PSTN lines. PSTN phone lines take analog samples of sound 2400 times/second.
Shit man! PSTN sucks.
by James T. Carson April 04, 2006