e customer enters the destination address of the call (otherwise known AT&T Long-Distance Switches Figure 3-6 Predivestiture connectivity AT&T Local Switches 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 as a telephone number). The switch receives the telephone number and analyzes it, determining from the area code and prefix information whether the call can be completed within the local switch or must leave the local switch for another one. If the call is indeed local, it merely bur- rows through the crust of the switch and then reemerges at the receiving local loop. If the call is a toll or long-distance call, it must burrow through the hard crunchy coating of the switch, pass through the soft chewy cen- ter, and emerge again on the other crunchy side on its way to a long- distance switch. Keep in mind that the local switch has no awareness of the existence of customers or telephony capability beyond its own cabi- nets. Thus, when it receives a telephone number that it is incapable of processing it, hands the number off to a higher-order switch, with the implied message, "Here-I have no idea what to do with this, but I assume that you do." The long-distance switch receives the number from the local switch, processes the call, establishes the necessary connection and passes the call on to the remote long-distance switch over a long-distance circuit. The remote long-distance switch passes the call to the remote local switch, which rings the destination telephone, and, ultimately, the call is established. Please note that in this predivestiture example, the originating local loop, local switch, long-distance switch, remote local loop, and all of the interconnect hardware and wiring belong to AT&T. They are mostly manufactured by Western Electric, based on a set of internal manufac- turing standards that, were there other