Hardware Tools and Media Testers

Network media test equipment is available to install and verify new cabling systems as well as to diagnose and maintain the existing physical infrastructure. At the lower end of the spectrum, there are breakout boxes, cable testers (scanners), volt-ohm meters (VOMs), and digital volt ohm meters (DVOe s). At the higher end of the spectrum, there are time domain reflectometers (TDRs) and optical TDRs (OTDRs). Go to websites such as www.flukenetworks.com, www.blackbox.com, and www.microtest.com for more information.

• Breakout boxes check signals and pinouts for RS-232 serial devices.

• VOMs an" DVOMs test continuity, voltages, current, resistance, and physical connectivity.

• Cable testers an" scanners, although at the lower end of the troubleshooting spectrum, are good in continuity situations, whether it be installation, maintenance, or support. A cable tester may help you determine whether the port is actually bad on the router or switch, for instance. Many handheld testers today display helpful address and protocol statistics as well. Figure 2-11 shows the Fluke handheld device.

Figure 2-11. Fluke Handheld Tester

Figure 2-11. Fluke Handheld Tester

• TDRs are at the higher end of spectrum and are good for cable-break issues. They test for consiste ncy in the impedance over the length of the cable. An electro nic pulse is sent to quickly detect shorts, breaks, and throughput issues. You used to really need TDRs for coax cable, but cable scanners work just fine today for twisted-pair cable.

• AnOTDR is a tim e domain reflectometer for fiber. It uses o ptical pulses to check signal loss. A good flashl ight, b elieve it or not, wMI get you mosr ofth e problems. Figure 2- 12 shows a fiber tester. TDR products are great, bu t age norm ally very expens i ve. If yo u are t te wicing cont racto^ h owever, this is a must for your tool bag.

Figure 2-12. OmniFiber Tester

Figure 2-12. OmniFiber Tester

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