DSL (Digital Subscriber Line) makes use of the unused frequency spectrum of the twisted pair telephone cables by carrying a digital signal without interfering with the voice service.
ETSI is very active in the definition of physical layer standards for DSL technologies including DSL 'splitters' required to separate voice and data. The work originated with the concept of Integrated Services Digital Network (ISDN), and the so-called xDSL family has continued to grow ever since.
ETSI Plugtests™ Service have organized successful DSL interoperability events for Triple Play over DSL and other broadband access technologies.