ble pair problem. They are asked to reach as far as they possibly can into the mass of wire on the horizontal side of the frame and feel for the wire that is moving, so that they can then wig- gle it to help a technician farther down the MDF locate it and trace it to locate a problem. The new tech, now bent over and reaching deep into the frame holding a wire pair, doesn't realize that another technician is now on the vertical side of the frame, reaching into the wire mass with a wire lasso, which is slipped over the new tech's arm and tied tightly to the far side of the frame. The technicians then go to lunch, leaving the new tech wired in place. Naturally, other technicians ignore his pleas for help; they remember their own experiences all too well. From the MDF, the cable pairs are connected to the local switch in the office. Figure 3-35 shows a Lucent #5ESS local switch. Remember that the job of the local switch is to establish temporary connections between two or more customers who wish to talk, or between two computers that wish to spit bits at each other. The line units (LUs) on the switch provide a connection point for every cable pair served by that particular switch in the office. Conceptually, then, it is a relatively simple task for the switch to connect one subscriber in the switch with another subscriber in the same switch. After all, the switch maintains tables-a directory, if you will-so it knows the subscribers to which it is directly connected. Far more complicated is the task of connecting a subscriber in one switch to a subscriber in another. This is where network intelligence becomes critically important. As we mentioned earlier, when the switch 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 Figure 3-35 Lucent 5ESS switch receives the dialed digits, it performs a rudimentary analysis on them to deter