Autotest
Autotest Results for Twisted Pair Cabling
3
3-21
ACR@REMOTE
The ACR@REMOTE test is identical to the ACR test, except that the ACR values
are calculated using NEXT@REMOTE values.
Return Loss (RL)
The RL test measures the difference between a test signal’s amplitude and the
amplitude of signal reflections returned by the cabling. The results of the RL test
indicate how well the cable’s characteristic impedance matches its rated
impedance over a range of frequencies.
The first RL results screen shows the cable pairs tested, the worst-case RL margin,
and a PASS or FAIL result for each pair. To see detailed results for the cable
pairs, use D U to highlight a pair; then press @ View Result. Table 3-6
describes the items on the RL results screen.
For TIA and ISO test standards, RL is not evaluated where attenuation at the same
frequency is less than 3 dB.
Table 3-6. Items on the RL Results Screen
Item Description
Pair
The cable pair relevant to the results.
Result
The overall result for the RL test. A PASS result means that the measured RL
is lower than the specified limit for the selected test standard. A FAIL result
means that the measured RL is higher than specified limit.
RL
The worst margin and worst RL. The worst margin is the RL value that is
closest to falling below specifications, or the value that exceeds specifications
by the greatest amount. The worst RL is the lowest RL value measured.
Frequency
The frequencies where the worst margin and worst RL values occurred.
Limit
The lowest acceptable RL values for the frequencies above.
Margin
The differences between the RL values and the limits. A positive number
means that the worst-case RL is better than the limit. A negative number
means that the worst-case RL exceeds the limit.
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