This tutorial provides an overview of ADSL technology and focuses on the physical layer as defined in ANSI T1.413-1998. From the introduction: "The demand for high-speed data networks in the "last mile" has driven the need for robust, interoperable, and easy to use multi-vendor Digital Subscriber Line (DSL) access solutions. DSL collectively refers to a group of technologies that utilize the unused bandwidth in the existing copper access network to deliver high-speed data services from the distribution center, or central office, to the end user. DSL technology is attractive because it requires little to no upgrading of the existing copper infrastructure that connects nearly all populated locations in the world. In addition, DSL is inherently secure due to its point-to-point nature."