PoE Passive Power RJ45 DC over Ethernet Adapter Cable PoE Splitter

This is a simple Power over Ethernet (PoE) solution that lets you power devices over a regular Ethernet (RJ45) cable — without needing a PoE-capable network or switch. It usually comes in a pair:
Injector – Adds DC power (from a wall adapter) into the Ethernet cable.
Splitter – At the other end, it splits out the DC power and Ethernet data so your device gets both.

These cables are typically passive — meaning they don’t negotiate power with the device like IEEE 802.3af/at PoE does, instead the voltage you feed in is delivered down the cable directly.

How It Works
Injector Cable: Has an RJ45 on one side and a DC barrel input + RJ45 on the other. You plug your normal power adapter into the barrel, and this feeds DC into the unused Ethernet pins. 

Splitter Cable: At the remote end, it has an RJ45 that receives power + data, and splits that into:
A regular RJ45 for network data
A DC barrel (typically 5.5 × 2.1 mm) for power to your device. 
The whole point is to use one Ethernet cable to carry both power and data, so you don’t need separate power wiring.