They have an integrated PoE injector to apply the regulated 18VDC to the CAT5 Ethernet cable. The input voltage must be between 9VDC and 36VDC.
They accept data-in to a shielded RJ45 Jack and provide data-out and PoE power on the shielded RJ45 output jack.
They work by supplying power on the unused Ethernet pins 4,5(V+) and 7,8(V-).
They have various protections for surge, short circuit, and overload. The units have a power output of 18W.