The ADSL concept
Asymmetric Digital Subscriber Line (ADSL) is a modem technology, which converts existing twisted-pair telephone lines into access paths for multimedia and high speed data communications.
An ADSL modem is connected to a twisted-pair telephone line, creating three information channels: a high-speed downstream channel (up to 1.1MHz and 2.2MHz for ADSL2+) depending on the implementation of the ADSL architecture, a medium-speed upstream channel (up to 135kHz or 230kHz) and a POTS (Plain Old Telephone Service), split off from the modem by filters.