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NReiling
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Why does the GPeR have two sets of jumpers?

Sun Jun 27, 2021 3:56 am

From looking at other posts, photos, etc. it seems that the GPeR is designed basically symmetrically, with the exception of engravings on the case indicating one side for "PoE In" and the other side for "PoE Out". All of the documentation I can find only ever suggests pulling the out-side jumpers, which prompts the question: why have jumpers on the in-side at all?

I hypothesized that this could be so that the device is fully-ambidextrous, and if you need to disable PoE passthrough, you need only pull the jumpers on the downstream side, but I did some testing to the best of my ability (i.e. very rudimentary) and discovered the following:

  • With jumpers intact, the device powers on when receiving passive voltage from EITHER the IN or the OUT side.
  • With EITHER or BOTH sets of jumpers removed, the device powers on when receiving passive voltage on the IN side, but not when receiving voltage from the OUT side.

So, the device itself is not ambidextrous, but the jumpers sort of are, at least based on this testing.

Any ideas as to why there are two sets of jumpers?
 
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hyppen
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Re: Why does the GPeR have two sets of jumpers?

Wed Jun 30, 2021 6:55 pm

All 4 jumpers are for PoE-Out only. Engravings are port labels. 802.3at/af can have power on any of 4 signal pairs: https://en.wikipedia.org/wiki/Power_ove ... et#Pinouts Thus you need 4 power connections for full compatibility and 4 jumpers to fully isolate any power source. I wouldn't test it with random jumper combinations - could end up feeding GPER only positive power and have bad ground loop trough remote side or something. If you need to know the exact wiring better ask MT or measure RJ45 pins against jumper pins with multi-meter on unpowered GPER.

Removing only one set of jumpers might be due to need to ensure ground continuity or some other function in most use cases. All jumpers are probably for special situations.
 
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Re: Why does the GPeR have two sets of jumpers?

Wed Jun 30, 2021 7:10 pm

Simply each side have it's own + and -
2 side X 2 polarity = 4

When you remove the plug from the wall outlet you detach bot Phase and Neuter (and Earth)

You can choice what side power the GPeR
 
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dcordovez
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Re: Why does the GPeR have two sets of jumpers?

Wed Jun 30, 2021 9:00 pm

we just bought a GPER we had the same doubt. But WARNING !, I suggest before using it to do tests with a tester that allows you to verify that no power passes to the other side when using a
passive poe injector
. In our case we used to test a ubiquiti 24V passive poe injector that we had in stock.

We follow the instructions and remove the jumpers on the "POE OUT" side of the GPER.

We connect the injector on the POE IN side of the gper, and on the POE OUT side a long cable connected to a computer.

The computer detected the connection and everything seemed to work fine, until a few minutes later we felt a smell of something burned .. and it came from the computer, from its network port (which still worked). We put a network tester on the cable and to our surprise, the tester said that there was voltage on the cable (24v) but not in the correct way for a PoE, that is, somehow the voltage was passing to the other side of the gPER.

We then tried to remove the 4 jumpers, the gper was still working and no voltage passed to the other side... computer connection ok.
We also tried removing only the two jumpers from the POE IN, and the result was that no voltage passed either... computer connection ok.
But if we just remove the POE OUT jumpers, we get voltage on the other side. ..

I do not know if the problem was caused by the type / model of injector tested (a ubiquiti 24V passive white that came with an antenna), I was not able to try another.
 
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dcordovez
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Re: Why does the GPeR have two sets of jumpers?

Wed Jun 30, 2021 9:26 pm

Thus you need 4 power connections for full compatibility and 4 jumpers to fully isolate any power source. I wouldn't test it with random jumper combinations - could end up feeding GPER only positive power and have bad ground loop trough remote side or something. If you need to know the exact wiring better ask MT or measure RJ45 pins against jumper pins with multi-meter on unpowered GPER.
I totally agree with that.

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