Microsoft KB Archive/97899

= Troubleshoot Cable with Time Domain Reflectometer (TDR) =

Article ID: 97899

Article Last Modified on 9/30/2003

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APPLIES TO


 * Microsoft LAN Manager 2.2 Standard Edition

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This article was previously published under Q97899



SUMMARY
A Time Domain Reflectometer (TDR) is used to troubleshoot breaks in cabling. It measures the time between the sending of an electrical pulse along the cable to be tested and the pulse's reflection by a potential short or open on the cable. From this time difference, you can determine the location of a cable break. The TDR operates at the physical layer of the OSI layer, and is not concerned with the contents of transmitted signals.

One end of the cable is hooked into the TDR device, and the type of cable is chosen on the device (thin coaxial versus twisted pair, for example). If there is a break in the cable, this will be indicated by a status message that indicates whether the cable is &quot;open&quot; or &quot;short&quot; and at what location (for example, &quot;60 feet&quot;). To maximize correct results, turn off repeaters and bridges before attaching the TDR to the cable and connect from the end of a segment, rather than from a &quot;t&quot; or tap.

Because most TDRs use a positive pulse, and transceivers do not have positive voltage protection, it may be necessary to power down the network while doing a TDR test. Some TDRs, however, allow tests to be performed while the network is active.

Additional query words: 2.20

Keywords: KB97899

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