Fluke DSX-600 Technical Reference Handbook page 109

Chapter 3: Certify Twisted Pair Cabling
About dB Rules
Below this frequency,
insertion loss is less
than 3.0 dB.
Below this frequency, the
limit line for return loss is
black because RL is not
evaluated against the limit.
When the plot shows all
pairs, the limit line is red
where any pair was
evaluated.
GPU58.EPS
Figure 45. How the 3 dB Rule Shows on Plots
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