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NEXT passes, but the plot shows that measurements exceed the limit
For ISO/IEC standards, NEXT is not evaluated where insertion loss is less than 4 dB (the 4 dB rule).
Return passes, but the plot shows that measurements exceed the limit
Return loss is not evaluated where insertion loss is less than 3 dB (the 3 dB rule).
Return loss gives FAIL, FAIL*, or PASS* result
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Patch cord or cable impedance not 100 Ω
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Patch cord handling causing changes in impedance
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Excessive amount of cable jammed into outlet box
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Tight service loops in telecommunications closet
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Excessive untwisting of pairs at connector
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Poor quality connectors
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Cable impedance not uniform (poor quality cable)
Table 4-1. Diagnosing Twisted Pair Test Failures (cont.)
Diagnosing Twisted Pair Cabling Faults
Common Causes of Twisted Pair Test Failures
4
-continued-
4-5
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