PoE Injection question

I am finalizing my punch block for POE Injection so I can hub all my cameras on one block and remote mount my NVR anywhere on the network. I want to make sure I don’t juice something that shouldn’t be. What pins should the 48v be put on? I am using the B protocol for my wires. I have looked around but I haven’t found a definitive answer as most people just say to use an inline injector, which I don’t want to do.

This chart should explain it. As long as you use T568B on both ends of all cables you should be fine.
10/100 only uses four wires so ad-hoc (aka DIY/ power injector/splitter) devices can use the other four wires - (4,5,7, and 8) two power and two ground. But for “proper” 48 V systems adhering to the 802.3 standards require negotiations between the power supply unit and the end of line devices. I think that Jon talked out this in one episode.


Thank you much! I am running a 10/100 network so the extra pairs are going to be fed for POE from that block only. It is dedicated to my cameras and everything is wired under the B protocol so no issues. I can back wire the block with a couple daisy chained pairs and we are in business!

What a pain! No, not the PoE, but the cabling. I had used a handful of the commercially made patch cables I bought off Amazon and just chopped the ends off to put them in the punch block. After I got them all terminated nice and clean I hung the block and started connecting up all my jumpers to the NVR and nothing would connect. I figured for sure I had messed something up with my terminations. I bought an inexpensive cable tester… since why not, right? And when I tested them, everything was wired perfectly… backwards. All of my blue colored patch cables are wired in the B pattern but the ice cubes are all flipped over so the pattern doesn’t work for color if you cut them to direct wire. Guess I will reverse the wire color on my block. Could replace them all with bulk wire but I like the finish of the commercial ends. Oh well. Funny.

It’s quite old now, but I wrote up a tutorial about DIY PoE here:


You might find the design files for these injectors useful for ideas, too:

Here’s more ancient history: