Autotest
Autotest Results for Twisted Pair Cabling
3
3-19
ACR
The ACR test calculates the ratio of attenuation to crosstalk (ACR) for each
combination of cable pairs. ACR is expressed as the difference (in dB) between
the measured NEXT and attenuation values. ACR is calculated using values
obtained from the NEXT and attenuation tests.
The first ACR results screen shows the NEXT pairs and attenuation pair used to
calculate the ACR result, the worst-case ACR margin, and a PASS or FAIL
result for each set of pairs.
To see detailed results for the cable pairs, use D U to highlight the pairs; then
press @ View Result. Table 3-5 describes the items on the ACR results
screen.
For ISO/IEC 11801-2002 and EN50173:2002 standards, ACR is not evaluated
where attenuation at the same frequency is less than 4 dB.
Table 3-5. Items on the ACR Results Screen
Item Description
Pairs
The pairs used in calculating the ACR result. The pair not listed as the Atten.
Pair produced the NEXT used in the ACR calculation.
Atten.
Pair
The pair that produced the attenuation value used in calculating the ACR result.
Result
The overall result for the ACR test. A PASS result means that the calculated
ACR is higher than the value specified for the selected test standard. A FAIL
result means that the calculated ACR is lower than the specified value.
ACR (dB)
The worst margin and worst ACR. The worst margin is the ACR value that is
closest to falling below specifications, or the value that exceeds specifications
by the greatest amount. The worst ACR is the lowest ACR value measured.
Frequency
The frequencies for the worst margin and worst ACR values.
Limit
The lowest ACR values acceptable for the frequencies above.
Margin
The differences between the ACR values and the limits. A positive number
means that the worst-case ACR is higher than the limit. A negative number
means that the worst-case ACR is lower than the limit.
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