or the delivery of one- way television signals, its shortcomings for other services should be fairly obvious to the reader. First of all, it is, by design, a broadcast system. It does not typically have the ability to support upstream traffic (from the customer toward the headend) and, therefore, is not suited for interactive applications. Second, because of its design, the network is prone to sig- nificant failures that have the potential to affect large numbers of customers. The tree structure, for example, means that if a failure occurs along any "branch" in the tree, every customer from that point downward loses service. Contrast this with the telephone network where customers have a dedicated local loop over which their service is delivered. Second, because the system is analog, it relies on amplifiers to keep the signal 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 strong, as it is propagated downstream. These amplifiers are powered locally-they do not have access to central office power as devices in the telephone network do. Consequently, a local power failure can bring down the network's ability to distribute service in that area. The third issue is one of customer perception. For any number of rea- sons, there is a general perception that the cable network is not as capa- ble or as reliable as the telephone network. As a consequence of this perception, the cable industry is faced with the daunting challenge of convincing potential voice and data customers that they are in fact capa- ble of delivering high-quality service. Some of the concerns are justified. In the first place, the telephone network has been in existence for almost 125 years, during which time its operators have learned how to optimally design, manage, and operate it in order to provide the best possible ser- vice. The cable