Well ,first off, in POE powered devices it is connected to device, and I'd imagine in many cases (of being cheap) it would be directly coupled to device. > So

Well ,first off, in POE powered devices it is connected to device, and I'd imagine in many cases (of being cheap) it would be directly coupled to device. > So running DC would probably just melt the cable or transformers but is not really likely to damage the device side (? Not actually sure about this). A step of voltage, whether that's just turning on AC on top of the cycle or just pushing DC thru it would go thru the transformer in form of short spike. So sure, looking at random transformer data they are protected to like 1000Vrms so it wouldn't jump thru isolation, but initial magnetic spike might, and then it is up to any surge protection on the other side to ground that > But in this case it runs mains AC.. so... Do we expect the cable to blow first due to the high current, saving the device, or do would we expect the brief period of AC would cause enough induced current on the device side to also fry that? I'd guess transformer would be the highest resistance/area thing in the chain so it would melt first.