A POE injector, which is also called as a “midspan,” injects power onto an Ethernet cable. Thus it combines power with data which is from a non-PoE switch or “endspan.” It has an external power supply.
The POE injector
is well suited for low-power installations where power outlets are not available. As a result, greater flexibility can be achieved by providing access to equipment installed in hard-to-reach areas with minimal impact on existing structures and budgets.