Digital subscriber line (
DSL; originally
digital subscriber loop) is a family of technologies that are used to transmit
digital data over
telephone lines. In telecommunications marketing, the term DSL is widely understood to mean
asymmetric digital subscriber line (ADSL), the most commonly installed DSL technology, for
Internet access. DSL service can be delivered simultaneously with
wired telephone service on the same telephone line. This is possible because DSL uses higher
frequency bands for data. On the customer premises, a
DSL filter on each non-DSL outlet blocks any high-frequency interference to enable simultaneous use of the voice and DSL services.