HDSL (High Bit-Rate DSL)

HDSL (High-Bit-Rate Digital Subscriber Line) is the earliest variation of DSL, and is commonly used as a substitute for T1 (Traditional T1) in the United States and E1 in Europe. The majority of DSL types are usually used for consumer service, but HDSL is not used in this fashion. This is because HDSL is most often used to replace traditional T1 and E1.

One way you can tell DSL is HDSL is that it is symmetrical, which just means that an equal amount of bandwidth is available in both directions. HDSL has the capability to transmit data at the same speed in both directions. HDSL is used between the telephone company and a customer.