3 db rule, 4 db rule, 12 db rule – Fluke Networks CertiFiber Pro Users Manual User Manual
Page 140: 62 db and 65 db rules
Versiv Cabling Certification Product Family
Technical Reference Handbook
118
3 dB Rule
At frequencies where insertion loss is less than 3.0 dB for a pair,
return loss for that pair is not evaluated against a limit.
4 dB Rule
This rule applies to the limits in Tables 3, 4, 5, and 6 and to these
limits:
EN 50173
Aus/NZ
JIS
At frequencies where insertion loss is less than 4.0 dB for the pair
used as the receive pair for the test, the measurements shown in
Tables 3, 4, 5, and 6 are not evaluated against a limit.
12 dB Rule
This rule applies to these test limits:
ISO11801 Channel Class E
A
ISO11801 PL Class E
A
If insertion loss is less than 12 dB for both pairs, the tester uses a
relaxed limit for NEXT. If the standard and relaxed limits both
apply to a plot, the plot shows both limit lines. See the
Knowledge Base on the Fluke Networks website for details.
62 dB and 65 dB Rules
If the result from the calculation of a limit value is more than a
specified value, then the limit is set to that value. For example, for
the ACR-F limit for the ISO Class E
A
test limit, if the calculation of
the limit value at a frequency gives a result that is more than
65 dB, then the limit at that frequency is 65 dB.