A form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide.
It does this by utilizing frequencies that are normally not used by a voice telephone call, in particular, frequencies higher than normal human hearing.
This signal will not travel very far over normal telephone cables, so ADSL can only be used over short distances, typically less than 5 km.
Once the signal reaches the telephone company’s local office, the ADSL signal is stripped off and immediately routed onto a conventional internet network, while any voice-frequency signal is switched into the conventional phone network.
This allows a single telephone connection to be used for both ADSL and voice calls at the same time.