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ADSL Modems Does the humble telephone lines play a major role in shaping the third millennium? Can a mere pair of thin copper wires twisted around each other transmit Internet data reliably and securely at blazing fast speed, making it possible to view high-quality moving images, sound and vast amounts of data on your personal computer screen or television? The answer is yes, as the growing success of DSL (digital subscriber line) technology abundantly demonstrates. The capacity of a communications channel depends on its bandwidth and its signal-to-noise ratio. A voice connection through a conventional phone network uses a bandwidth of about 3,000 hertz (Hz): from about 300 Hz to 3,300 Hz. An analog modem operating at 33.6 kilobits per second (kbps) requires a slightly wider bandwidth 3,200 Hz and needs a very good connection, one with a high signal-to-noise ratio. Modems operating at 56 kbps achieve their rates by taking advantage of digital connections that circumvent som