DSL Advances

16.1. The History of DSL and Telephony

DSL technology and telephony have been intimately associated from the invention of the very first digital line protocols. The ISDN basic rate interface (ISDN BRI) was developed to carry both digital voice and data (at rates between 64 Kbps and 128 Kbps) over the same phone line to environments such as residences, small businesses, and larger business sites using Centrex-type services. T1 carrier systems were originally created to provide digital trunk lines between telephone company facilities. Their use in what may have been the first “digital subscriber line” service to business customers for providing both private voice and data services to business customer premises was originally seen as providing telephony ...