 of an overvoltage Figure 3-29 Turbine in rooftop enclosure 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 Chapter 3 Figure 3-30 Distribution Frame, or MDF Figure 3-31 Vertical side of MDF, showing protectors 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 situation and protect the equipment and people in the office. A close-up of carbons is shown in Figure 3-32. The vertical side of the MDF is wired to the horizontal side. The hori- zontal side, shown in Figure 3-33, is ultimately wired to the central office switch. Notice the mass of wire lying on each shelf of the frame: These are the cable pairs from the customers served by the office. Imagine the complexity of troubleshooting a problem in that hairball. I have spent many hours up to my shoulders in wire, tugging on a wire pair while a technician fifty feet down the frame, also up to his elbows in wire, feels for the wire that is moving so it can be traced. The horizontal side also provides craft/technician access for repair purposes. In Figure 3-34, Dick Pecor has connected a test set to the appearance of a cable pair and is lis- tening for noise. Figure 3-32 Close-up of carbons Figure 3-33 Horizontal side of MDF 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 Chapter 3 Figure 3-34 Dick Pecor testing cable pair on horizontal side of MDF New technicians are usually given a trial by fire when they arrive for work at a switching office. One of the most common pranks is to ask them to help troubleshoot a ca