Definition: HDSL technology was developed in the early 1990s, making it one of the oldest forms of DSL. HDSL service provides equal bandwidth for both downloads and uploads, offering data rates up to 2,048 Kbps. Note that HDSL requires multiple phone lines to accomplish this.
Like other forms of DSL, HDSL features "always on" combined voice and data services. HDSL enjoyed some popularity in years past, but the technology has effectively been replaced by alternatives like SDSL that only require one phone line and offer similar performance and reach.
Also Known As: High-data-rate DSL, High-speed DSL
This multi-part article discusses the nuts and bolts of DSL technology, service availability, and more.
These directory pages link to the best online resources for DSL.