Question

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mid line ethernet switch

By mcgahon ·
Set up is

receiver....... cat5.........POE.......cat5.......router

I want to insert an externally powered ethernet switch midline between receiver and POE.
The wiring is 1 Blue 2 Blue/W 3 Orange 4 Brown 5 Brown/W 6 Orange/W
7 Green 8 Green/W This is the way the installers wired the whole system.
When I wire the RJ45 clips in this way and connect them to the switch, the POE and receiver shut down.

How should I wire the RJ45s ?

Thanks.

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All Answers

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If it's wired straight through, the color sequence does not matter

by robo_dev In reply to mid line ethernet switch

While obviously that's not EIA/TIA 568A or B, but as long as pin1 at one end goes to pin 1 on the other end, the color of the wire should not matter.

Are you saying that your cabling is NOT straight through?

If you plug the new switch directly into the POE device, does it work?
Are you using a POE-enabled switch or a dedicated POE power supply?

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Reponse To Answer

by mcgahon In reply to If it's wired straight th ...

The RJ45s are wired as per the existing system, B BW O Br BrW OW G GW, when the line from the POE is connected to the switch, the lights on the POE go out. This happens whether the switch is plugged into the mains or not. I have tried all permutations but still no joy. This is why I think the wiring might need to be altered.

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Reponse To Answer

by oldbaritone In reply to If it's wired straight th ...

UNTRUE! RJ45 wiring DOES matter!

Cat 5/5e/6 UTP cable has 4 twisted pairs. The pairing DOES matter. While you might get away with swapping a couple of colors, the cable is rated for use in accordance with the specification. Each "Send" signal has a corresponding "Return" signal, and the Send/Return pairs need to be kept together for the cable to work properly.

You can't just hook in 8 wires "any which way" and expect it to work. You might get dumb-lucky on a short cable, but your EMI will be horrendous.

It doesn't matter as long as both ends are 568A or 568B, but just because "pin 1 at one end goes to pin 1 on the other end" WON'T WORK! Keep your pairing correct, and use the standards!

http://en.wikipedia.org/wiki/TIA/EIA-568

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Wil the switch power up if plugged directly into the POE device?

by robo_dev In reply to mid line ethernet switch

I would assume that the answer is yes? Note that there is more than one POE standard, and multiple 'modes' within each standard.

I would test the cable-run with a cable tester to verify that all eight wires have been properly punched-down at each end. It would be possible that the original installer simply installed the cable wrong.

POE is basically just running 30VDC over the wire, using the two unused pairs.

POE Specs:
"Mode A has two alternate configurations (MDI and MDI-X), using the same pairs but with different polarities. In mode A, pins 1 and 2 (pair #2 in T568B wiring) form one side of the 48 V DC, and pins 3 and 6 (pair #3 in T568B) form the other side. These are the same two pairs used for data transmission in 10BASE-T and 100BASE-TX, allowing the provision of both power and data over only two pairs in such networks. The free polarity allows PoE to accommodate for crossover cables, patch cables and auto-MDIX."

"In mode B, pins 4-5 (pair #1 in both T568A and T568B) form one side of the DC supply and pins 7-8 (pair #4 in both T568A and T568B) provide the return; these are the "spare" pairs in 10BASE-T and 100BASE-TX. Mode B, therefore, requires a 4-pair cable."

http://en.wikipedia.org/wiki/Power_over_Ethernet

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