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Copper Line Tests: Difference between revisions
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→Meaning of the results
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If you get a Copper line test error, try the test again with all equipment unplugged, and the NTE5 faceplate removed as the fault could be caused by local wiring or equipment.
More info on Loop and resistance faults:
Loop fault is a symmetric low DC resistance between A/B wires in the pair. Rectified loop fault is an asymmetric low DC resistance between A/B, as-if there's a diode shorting the fault.
At DC, the line should appear as an open circuit (infinite resistance).
A loop test (among other things) applies a known DC voltage to the line, and measures the current flow - it should see 0 mA current flow with phones all on hook. It then reverses the DC voltage, and expects to see 0 mA again.
If it sees current flow when it applies voltage, you have a loop fault. If the current is different depending on whether A or B is +ve relative to the other, you have a rectified loop fault.
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