Bit of an electrical dolt, but replaced an existing wireless radio with a new radio that was powered via PoE from the switch. Using same Cat5 cable, into the same PoE port on the switch, we couldn't power up the new radio.
Fearing that we'd fry the gear, I didn't want to plug the Cat5 patch cable that was currently plugged into the PoE switch port into the LAN port of the PoE injector that came with the new radio. I fearfully tried it and it worked (as in the data link was now completed and all was well).
Question: is there a "shut-off" or "killswitch" routine that happens when a device is plugged into a PoE device or is it just that the LAN port on the PoE injector is not expecting/"requesting" PoE so it doesn't get provided by the switch?