 entering the DSL marketplace. The Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Access Technologies Access Technologies first step that they can take is to prequalify local loops for DSL service to the extent possible. This means running a series of tests using mecha- nized loop testing (MLT) to determine whether each loop's transmission performance falls within the bounds established by the service provider and existing standards and industry support organizations. For DSL prequalification, MLT tests the following performance indi- cators (and others as required): Cable architecture Loop length Crosstalk and background noise 56K modems, ISDN, and DSL represent the primary access technolo- gies that the telephone companies offer. Recently, however, a new con- tender has entered the game: the cable provider. The section that follows describes the technology they offer and the role that they play in the evolving access marketplace. Cable-Based Access Technologies In 1950, Ed Parsons placed an antenna on a hillside above his home in Washington State, attached it to a coaxial cable distribution network, and began to offer television service to his friends and neighbors. Prior to his efforts, the residents of his town were unable to pick up broadcast channels because of the blocking effects of the surrounding mountains. Thanks to Parsons, community antenna television (CATV) was born; from its roots came cable television. Since that time the cable industry has grown into a massive industry. In the United States alone 15,000 headends have the ability to deliver content to more than 150 million homes in more than 50,000 communi- ties over more than 1 million miles of coaxial and fiber-optic cable. As the industry's network has grown, SO too have the aspirations of those deploying it. Their goal is to make it much more than a one-way medium for th