Certifying Twisted Pair Cabling
Twisted Pair Autotest Results
3-23
3
ACR (Attenuation to Crosstalk Ratio)
ACR is like a signal-to-noise ratio. ACR values indicate how
the amplitude of signals received from a far-end transmitter
compares to the amplitude of crosstalk produced by near-
end transmissions, as shown in Figure 3-16. The tester
calculates ACR as the difference (in dB) between NEXT and
attenuation (insertion loss). Higher ACR values mean
received signals are much larger than crosstalk signals.
Higher ACR values correspond to better cabling
performance.
Figure 3-17 describes the ACR plot.
amd91f.eps
Figure 3-16. Attenuation to Crosstalk Ratio (ACR)
Far-end
signal
source
Crosstalk
Near-end
signal
source
Crosstalk - Received Signal = ACR
Crosstalk and
signal received
from far end
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