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
. 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.