PSTN

(Public Switched Telephone Network) The worldwide voice telephone network. Once only an analog system, the heart of most telephone networks today is all digital. In the U.S., most of the remaining analog lines are the ones from your house or office to the telephone company's central office (CO). See POTS and AIN.

Switched, But Not Too Public

In 1886, this 50-line magneto switchboard, made by Bell Telephone of Canada, was used to switch voice calls in small localities. These instruments were the beginning of the worldwide PSTN. (Image courtesy of Nortel Networks.)

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PSTN - Public Switched Telephone Network