What is “PoE?”

I know what you’re thinking, PoE is a 19th century horror writer best known for “The Raven?” What, you’re not thinking that? Perhaps you’re not a high school English teacher. After all, there are a limited number of them. Besides, this isn’t a blog known for discussing 19th-century gothic horror writers. I’m sure there is a blog like that, but this isn’t it.

What PoE actually means

PoE is an acronym standing for Power over Ethernet. Don’t ask me why the “o” in “over” isn’t capitalized, let’s be honest I’m having a hard enough time keeping on topic here.

Power over Ethernet is a way that access points, cameras and other devices can work without being near a power outlet. The Ethernet cable itself carries power on two wires which would otherwise not be used. Therefore, a device that’s plugged into a PoE cable doesn’t need a separate power cord. This makes installation easier and means that something like a security camera can be placed almost anywhere that a single Ethernet cable can reach. The voltage is very low – typically 24 volts – so that there is little danger in running cable through any space. 24 volts shouldn’t generate excess heat or create any problems in an otherwise safe installation.

How PoE is used

PoE usually requires a “PoE injector” which plugs into an outlet. An Ethernet cable goes to the router or switch, and another Ethernet cable, containing power, goes out to the device that needs it. We have a decent selection of them here, and you can also buy industrial routers and switches that have this feature built in. Your average run of the mill router or switch won’t have this feature, because it adds cost to something that’s usually considered a budget item.

Why isn’t this in every setup?

It’s always best to make sure that a PoE line is not used for a regular Ethernet connection. While most PoE injectors will only power the line if it is needed, there is always a possibility that a device will receive 24 volts over the Ethernet cable when it doesn’t need it. For that reason you should always make the effort to tag PoE cables so someone working with your system in the future will know that they are there. Some installers reserve red category cables for lines carrying power. This isn’t a standard though. If you leave an install and someone else comes in, they may not understand your color scheme.

Solid Signal: Your home for PoE injectors and more

When you want to shop for networking equipment, you want to know you’re dealing with experts. You might find a bigger selection of network equipment at the world’s largest online retailer. That’s true. But, you won’t find the expertise. Those folks don’t even answer the phone. On the other hand, we do. If you have questions before, during or after the sales process, call us! We’re here during East Coast business hours. Just call 888-233-7563. You’ll reach someone in our US corporate offices. We don’t read scripts. We read owners’ manuals so you don’t have to. Give us a try! If it’s after hours, fill out the form below. We’ll get back to you, usually within one business day.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 10,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.