oad Roswell To Ruidoso To Albuquerque To Corpus To Clovis To Houston 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. Telephony Telephony Trunks, lines, feeders, local access spurs, switches, routers-all terms used commonly in the telecommunications industry. Trunks are high- bandwidth, long-distance transport facilities. Lines, feeders, and local access spurs are local loops. Switches and routers are-well, switches and routers. And the overall function of the two is exactly the same, as is their goal of delivering their transported payload in the most efficient fashion possible. When Bell's contraption first arrived on the scene it wasn't a lot more complicated than a railroad, frankly. As we noted earlier, there was no initial concept of switching. Instead, the plan was to gradually evolve the network to a full mesh architecture as customers demanded more and more connections. Eventually, operators were added to provide a manual switching function of sorts, and over time they were replaced with mechanical, then electromechanical, then all-electronic switches. Ulti- mately, intelligence was overlaid in the form of signaling, giving the net- work the ability to make increasingly informed decisions about traffic handling as well as to provide value-added services. Now that you understand the overall development strategy that Bell and his cohorts had in mind, as well as the basics of switching, we turn our attention to the inner workings of the typical network, shown in Figure 3-9. I must take a moment here to thank my good friend Dick Pecor, who created this drawing-from his head, I might add. Thanks, Dick. Scalpel, please. Figure 3-9 Typical network Switch Switch Optical LU TU TU LU Williston CO Charlotte CO Tandem Switch Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-