Troubleshooting and FAQ’s 7-2
What type of testing is available on coax and non-data
cables?
Coax cables can only be tested for length and wire map
(open/short/terminated) because only one physical pair (center
conductor and shield) is present. At least two pairs are required to
perform an Ethernet cable performance test.
When testing two-or three-pair cables such as telephone, speaker,
or alarm wire a wire map, length, and cable performance test can
be run. However, for the cable performance test to run the cable
must be terminated in accordance with the TIA 568-A/B wiring
configuration (see Table 1-1 Ethernet Signaling).
Note: While it is possible, attempting to run a
cable performance test on alarm or flat telephone
wire may result in a failed link establishment or
BERT because of excessive crosstalk in cables
that are not twisted at a rate to support 10Mbps or
higher data rates.
How does monitoring mode work?
Monitoring is similar to a very long autotest. In the interest of
productivity, the default test time (minimum required by IEEE) is
ten seconds for the cable performance test. When manually
configuring a longer test time such as several minutes or several
hours, the likelihood of discovering bit errors during the cable
performance tests increases. Statistically, the longer the device is
transmitting data, the more likely an error will occur.
Monitoring mode is an alternative troubleshooting device, and
should be used when the user believes that there is a problem with
a particular cabling link, even though a brief autotest passes
without any bit errors. Running a longer test may capture errors
that are a result of environmental conditions such as sources of
intermittent electrical noise that interfere with data transmission on
the network.
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