The following lines were added (+) and removed (-):
DSL works by transferring voice and data simultaneously over the existing twisted-pair copper telephone lines by using different frequency ranges on the same line. A DSL modem at the customer residence sends data over the phone line to a DSLAM at the CO. The DSLAM is what terminates and aggregates incoming ADSL lines. The DSLAM redirects voice to the PSTN and data to the Internet backbone connection.