Review on 💡 PoE Texas GPOE-1B: Gigabit Passive PoE Injector - Combining 10/100/1000 Data and DC Power on RJ45 for PoE, 2.1mm x 5.5mm DC Connector Accepting 12-56v DC (Power Supply Excluded) by Sam Kriegshauser

This is a very stupid PoE injector. Not stupid like a bad injection, stupid like you're just one step away from connecting the power source to the cable. I was testing a Raspi4 setup with a Uniview camera when I was having trouble powering the camera via PoE, but PoE worked to power my Raspi. After a while with a multimeter I tracked this down when I plugged my power supply directly into the camera, it switched from nominal 12v to nominal 48v but this only fed the nominal 12v and never tripped the switch in the power supply out. Open and yes. Your typical cheap switching power supply doesn't stand a chance, higher quality consumables will work, but be careful when choosing a power supply.