This question refers to Power over Ethernet (PoE) devices that operate using the Institute of Electrical and Electronics Engineers (IEEE) 802.3af/at/bt protocols.

Ethernet switches and access points connect to terminal (end of cable) equipment, such as security cameras, IP phones, etc., using 8-wire category rated 5/6/7 data cable. Category data cable is numbered to represent different specifications, such as frequency, impedance, and other unique category specs.

However, all category data cables have a maximum length of 328 feet (100 meters). For cable installations longer than 328 feet, both data and PoE voltage degradation occurs. Category Ethernet cables include the following: CAT5, CAT5e, CAT6, CAT6a, CAT7.

For category  cable lengths exceeding 328 feet, you can use a PoE injector or PoE extender. Both devices boost the data and voltage levels for another 328 feet.

Boosting both the data and PoE power requires a power supply providing a DC voltage to a PoE midspan injector. The injector accepts an incoming data-only port and a separate PoE (power) port. Internally, the midspan injector combines both for a shared data+PoE output.

Using a PoE injector extends the category data cable another 328 feet (100m). However, as noted, a separate power supply is needed for the injected power port. The power supply can be AC power-fed or DC power-fed, both of which require the appropriate AC/DC power source.

Midspan PoE injectors come with a power adapter or power supply that adapts an AC input to a DC output needed for the injector's PoE (power) port input. For injectors that have an integrated power adapter; only an AC power cord is needed. Some come without a power supply/adapter; in such cases, the PoE power is provided by the customer's equipment (an Ethernet switch, for example).

The outdoor PoE injector mentioned above, and the outdoor PoE splitter (shown below) also provide surge protection against induced lightning strikes. To avoid installing both a PoE power cable and a separate data cable (up a tall tower, for example), using an Ethernet injector at the tower base and an Ethernet splitter at the tower top can solve this issue. The Ethernet splitter accepts the single combined data+PoE cable and separates the PoE and data for tower top non-PoE equipment requiring separate data and PoE power.

Finally, an Ethernet extender provides a similar boost to data and PoE power without a separate power source. For locations where an AC or DC power source is not present or does not provide sufficient power for a midspan injector, use an Ethernet extender. This device uses the PoE power from a single combined data+PoE input cable to boost the data and PoE voltage. It requires only one cable in and one cable out.