THE FAULT LIBRARY
Read the wiring.
Understand the failure.
A visual reference for common copper-cable faults, with a field record for your own measurements.
Open conductor
One path is interrupted. Wiremap can identify the affected conductor; a suitable distance function may help locate the fault.
Explanatory schematic · not a test resultReversed pair
The two conductors of a pair are swapped at one end. This is a pin-mapping error, not a split pair.
Explanatory schematic · not a test resultCrossed pairs
Two complete pairs exchange positions. Whether equipment tolerates a crossover is different from whether the installed link meets its required wiring scheme.
Explanatory schematic · not a test resultFAULT / 04
Split pair:
continuity can still pass.
Pins connect one-to-one at both ends, but the conductors used for a signal pair are no longer physically twisted together. A basic DC continuity check can miss it.
For example, exchanging the conductors on pins 4 and 6 at both ends preserves pin continuity, while breaking the intended 3–6 and 4–5 pairing. It is the physical pair membership that matters.
Work through the symptom →EXPECTED ETHERNET PAIRS
Matching pin numbers alone does not verify these pairs.
TAKE IT TO THE JOB
Your next measurement,
properly recorded.
One blank row. Equipment, cable, fault, mode, result and retest.
No example readings to mistake for measured data.
What this library contains
This library explains opens, reversed pairs, crossed pairs and split pairs using simplified schematics. It contains no measured fault samples. Use the field-record template to identify your own cable, test setup, observed result and repair; a diagram alone does not establish how a particular tester will respond.
Illustrations are our own. Technical references: FOA wiremap guide and Fluke split-pair identification. See our test methodology.