Cable Diagnostic Question

icpilot

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Recently upgraded my POE switch to a fully managed Aruba 2500. Now I have a ton of bells and whistles to play with, one of them being cable diagnostics with TDR (Time-Domain Reflectometer). One of my cable runs to a camera produced this result:

Interface name : gigabitethernet0/0/12
Test status : Completed
Normal cable length : 0 metres

Pair 1-2
--------
Pair status : Normal

Pair 3-6
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Pair status : Normal

Pair 4-5
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Pair status : Open
Distance fault : 6 metres

Pair 7-8
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Pair status : Short
Distance fault : 11 metres

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That same cable PASSES the cable test on my Southwire M300P network cable tester. Several other cables also indicate concerning results from the TDR diagnostic.

Running a simple PING from that same switch through the cable to the camera produces:

Sending 5, 100-byte ICMP Echos to 192.168.1.120, timeout is 2 seconds: !!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0.365/6.602/25.228 ms

_

Should I be concerned about the TDR diagnostic showing an OPEN pair and a SHORTED pair on the cable, or am I reading the diagnostic incorrectly?
 

TVille

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Is the cable connected at the far end when running the test? I would disconnect it and rerun it if so.
 

icpilot

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Is the cable connected at the far end when running the test? I would disconnect it and rerun it if so.
Yes, it's connected to a camera. I can re-run, with the expectation it should then show OPEN for the first 2 pairs. Seems really odd that the fault distance for the OPEN pair would be different, and shorter, than for the SHORTED pair. I didn't measure the cable when installing, but 6 meters (about 20 feet) sounds about right.
 

alastairstevenson

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Seems really odd that the fault distance for the OPEN pair would be different, and shorter,
PoE cameras typically have 4&5 and 7&8 shorted, to support a PoE mode.
I'd have expected both those pairs to give the same 'short' diagnostic, unless the ethernet transformer in the camera is confusing the reflected signal.
 

Carl

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Does this mean most cameras are using mode A wiring? Could I use one of those pairs on the relay output of the camera to trigger an Arduino port? I am considering a new Amcrest camera and would like to take advantage of the smart human detection to trigger my porch light connected to my automation system. It looks like you can set human detection to trigger the relay output, but I don't have another pair of wires available at the camera. I would separate the pair before the connector at each end leaving that pair open at the switch and camera. Would this work or cause any problems?

Thanks for any input.
 
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