Networks Europe March/April 2019 - Page 31

CABLING 31 By Mark Mullins, Marketing Manager & Founding Member, Fluke Networks A close look at identifying a range of different types of cable failures alongside how and why they occur While the most common causes of failures in twisted pair cabling include installation errors, defects found in poor- quality components (cables, connectors and patch cords etc.), damage to the installed cable and incorrect tester set- up, sometimes technicians want to know specifically WHY a link failed. Based on which performance parameter failed testing, there are specific possible causes that a technician can consider. Let’s take a closer look. Failures of the five wiremap tests When it comes to wiremap testing that lets you know that you have continuity and that each conductor of a four-pair cable is connected correctly to the corresponding pin at the far end, there are five specific tests performed: open, short, reversed pair, crossed pair and split pair. And each one of these has potential causes to consider. If wiremap testing results in an open, the conductors may be broken at a connection point, connected to the wrong pins at the far end or not properly punched down to make contact within the IDC tower. There’s also the possibility of a break in the cable or a damaged connector. A short can also indicate improper termination or a damaged connector or cable, but it could also indicate conductive material stuck between pins at a connection point. Other wiremap tests are easier to pinpoint the specific cause. In reversed pair, crossed pair and split pair results, the cause is almost always conductors connected to the wrong pins at the far end. A crossed pair result can also be caused by mixing 568A and 568B wiring or the use of crossover cables.