was (and is) quite simple: Invoke the Wizard of Oz Protocol-when a computer is doing the talking, the modem must make the network think it is talking to a telephone. "Pay no attention to that man behind the curtain!" Over time, modem technology advanced, allowing the local loop to pro- vide higher and higher bandwidth. This increasing bandwidth was made possible through clever signaling schemes that allowed a single signaling event to transport more than a single bit. These modern modems, often called "Shannon-Busting modems" because they defy the limits of sig- naling defined by Shannon, are commonplace today. They allow baud lev- els to reach unheard-of extremes and permit the creation of very high bit-per-signal rates. The analog local loop is used today for various voice and data applica- tions in both business and residence markets. The new lease on life it enjoys thanks to advanced modem technology as well as a focus by installation personnel on the need to build clean, reliable, outside plants has resulted in the development of faster access technologies designed to operate across the analog local loop, including traditional high-speed modem access and such options as DSL. 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 Marketplace Realities According to a number of demographic studies, there are approximately 100 million households today that host home-office workers, and the number is growing rapidly. These numbers include both telecommuters and those who are self-employed and work out of their homes. They require the ability to connect to remote LANs and corporate databases, retrieve e-mail, access the Web, and, in some cases, conduct videoconfer- ences with colleagues and customers. The traditional bandwidth-limited local loop is not capable of satisfying these requirements with traditional 