A PoE injector (or a PoE splitter, more on that later) can be implemented to make a non-PoE compatible switch work with PoE devices, without the headache – or the price tag – of upgrading your switches.

Rather than having to painstakingly run a data cable and a power cable from a network switch to a Powered Device (PD), Power over Ethernet (PoE) saves both time and money by sending data and power over the same cable.

PoE installation is fast and cheap, especially when compared to older, outdated methods that require two separate cables – one for power, and one for data.

A PoE switch can transmit both data and power from each of its ports. However, older switches without PoE capabilities can’t be used with PoE devices, as they are only capable of transmitting data, not power.

So, what do you do when you have a few PoE compatible PDs in your home or office – such as an IP camera, a Wireless Access Points (WAP), or an IP phone – but you don’t have a PoE switch?

Luckily for you, you won’t have to upgrade all of your existing switches to PoE compatible switches just to take advantage of PoE technology.

What is a PoE Injector?

Although PoE compatible switches exist, many homes, offices, and businesses have non-PoE switches already installed.

Evidently, replacing the millions of non-PoE compatible switches is not a viable solution, nor is unnecessarily running two cables – one for power and one for data – to a device that could be operated with just one cable.

A PoE injector is a device used to add power to an Ethernet cable for PoE equipment.

How do You Use a PoE Injector?

PoE injectors have three ports:

A power input, a data input, and a power/data output. Simply connect an Ethernet cable from a non-PoE switch to the injector, plug in the power cable, and then run a third PoE cable from the injector to your PoE enabled powered device.

POE-171A-60 Ports

PoE Injector Application Diagram

In essence, a PoE injector converts two inputs – a power cable and a data cable – into a single (PoE) output.

Rather than having to replace your existing infrastructure, a PoE injector is a cheap and easy way to use a few PoE devices with a non-PoE switch.

What is a PoE Splitter?

A PoE splitter functions oppositely of a PoE injector. Rather than taking both power input and a data input and turning them into a singular power/data output, a PoE splitter takes a power/data input and turns it into two separate outputs, one for power and one for data.

PoE Splitter Application DiagramA PoE splitter can be used to connect a non-PoE compatible device to a PoE switch, hub, or even to a PoE injector.

PoE Injector and Splitter Application DiagramWith a PoE splitter, you can run a PoE cable all the way to the PoE splitter located in close proximity to the powered device.

PoE splitters come in handy with older powered devices that can’t be used with PoE switches or hubs.

When is a PoE Injector Practical?

PoE injectors are wonderful when you need to install a low powered device in a hard-to-reach location without a power outlet nearby.

Hiring an electrician to install a power outlet is expensive on its own, not to mention the cost of breaking through walls, installing cables, etc.

PoE installation usually doesn’t require a professional, nor will it break the bank.

PoE injectors allow the installation of PDs in remote locations without costing a fortune or taking ages to successfully install.

Unfortunately, PoE injectors aren’t always a practical solution.

Take a large office building, for instance. Most offices have dozens of powered devices, such as IP phones, IP cameras, and Wireless Access Points, just to name a few.  

If you didn’t want to upgrade your non-PoE enabled network switches, you’d have to use a PoE injector for every single device on the network.

Sure, this wouldn’t be an issue if you were setting up a home network with only a few devices – on the other hand, as the network scales and more devices must be added, trying to use PoE injectors to solve the problem would quickly turn into a big jumbled mess of wires.

Evidently, a jumbled mess of wires and power cables is the problem that PoE aims to solve in the first place.

Fortunately, there is another solution for large enterprise networks known as a PoE hub.

PoE Hub

You can think of a PoE hub as a large PoE injector.

Instead of hooking up an individual PoE injector to each individual cable and a powered device, a PoE hub makes the process much simpler.

POE-1200G PoE Hub

The top row of ports are power/data output ports, and the bottom ports are for data input.

After plugging the hub’s power cable into a wall outlet, the hub will transmit power from each of its power/data output ports.

You can connect short Ethernet cables from your non-PoE switch to the data input ports of the hub. Next, connect a PoE cable from a power/data output port, and run that cable to your powered device.

PoE Hub Application DiagramHubs help to keep cable clutter to a minimum and render the installation process not only cheaper but easier as well.

If you’re only going to be connecting a few powered devices to your non-PoE switch, then purchasing a hub would be overkill. You wouldn’t use most of the ports, and you’d be wasting money.

On the other hand, if you’re connecting a dozen or more PoE devices to your network without a PoE enabled switch, purchasing a hub is definitely the way to go.

Things to Consider Before You Buy a PoE Injector

Before you buy a PoE injector, you need to make sure it’s right for you.

Although they are convenient, they’re not always the best solution.

Think about the following three things before you buy:

  • The number of devices: If you only need to connect one or two PoE devices to your old switch, then a PoE injector is definitely a viable option. Connecting two PoE injectors is relatively painless, inexpensive, and quick. On the other hand, if you have ten, twenty, or more devices to connect, using a PoE injector for each one would quickly turn into a jumble of messy cables everywhere. In this scenario, it’s best to use a PoE midspan (more on that later).
  • PoE Standard: There are several different PoE standards, ranging from 15 watts of Power over Ethernet all the way up to today’s 100 watt PoE standard. If your injector’s PoE standard is not compliant with either your switch or powered device, you’ll surely have some issues. Double check to make sure everything is compatible before making a purchase.
  • Voltage: Make sure your PoE injector’s voltage is compliant with your powered devices. For instance, most PoE security cameras either use 12 or 24 Volts. Check the specifications of your powered devices and your injector to make sure they’re compatible.