A PoE (or Power over Ethernet) injector is a small device which sends power over ethernet cables.

Occasionally only One or 2 units like as a warehouse telephone or IP camera is required to be powered via the Ethernet wire to simplify the install. A Power over Ethernet Injector will provide this power, one cable at a time. The majority of the PoE injectors are 802.3af compatible, meaning any kind of unit that supports 802.3af can easily be driven by these kinds of power over Ethernet injectors.

You may sometime hear PoE injectors being called midspans or midspan hubs, but don’t be confused as this is just another couple of terms for the same thing.

So why would you need to use a PoE Injector? Imagine you have a large warehouse and need to install an IP telephone. You no longer need to go to the hassle of having to run power to the location, because you can simply run power over the ethernet connection, via it’s RJ45 port.

Once only something available in the IT industry for large firms, power over ethernet is something which is rapidly becoming known about in the home consumer market. Being able to ‘inject’ low voltage power to a device, over the same cable you already use for data, is incredibly useful. Many homes nowadays are installing their own security cameras, so you can imagine how useful it is not to have to worry about running AC power to such a device.

When choosing a PoE injector, ensure you choose one which complies with the IEEE 802.3af power distribution standard. The IEEE is the Institute of Electrical and Electronic Engineers. This standard provides 48 Volts DC over 2 of the 4 pairs on category 3 and cat5 network cables, with max current of 400mA. Max load power would be 15.4Watts. A lot of numbers there, so in short, just ensure that whichever device you decide to go for in the end, complies with IEEE802.3af and you will be okay.