Power over Ethernet (PoE) Explained

Part 1 - An Introduction to PoE


What is Power over Ethernet?

Power over Ethernet (PoE) is a technology that lets network cables carry electrical power.

For example, a digital security camera normally requires two connections to be made when it is installed:

A network connection, in order to be able to communicate with video recording and display equipment

A power connection, to deliver the electrical power the camera needs to operate

However, if the camera is PoE-enabled, only the network connection needs to be made, as it will receive its electrical power from this cable as well.



Why use PoE?

Specifying Power over Ethernet brings many advantages to an installation:

Time and cost savings - by reducing the time and expense of having electrical power cabling installed.  Network cables do not require a qualified electrician to fit them, and can be located anywhere.

Flexibility - without being tethered to an electrical outlet, devices such as IP cameras and wireless access points can be located wherever they are needed most, and repositioned easily if required.

Safety - PoE delivery is intelligent, and designed to protect network equipment from overload, underpowering, or incorrect installation.

Reliability - PoE power comes from a central and universally compatible source, rather than a collection of distributed wall adapters.  It can be backed-up by an uninterruptible power supply, or controlled to easily disable or reset devices.

Scalability - having power available on the network means that extension and distribution of network connections is simple and effective.

Devices that use Power over Ethernet

PoE has many applications, but the three key areas are:

VoIP phones - the original PoE application.  Using PoE means phones have a single connection to a wall socket, and can be remotely powered down, just like with the older analog systems.

IP cameras - PoE is now ubiquitous on networked surveillance cameras, where it enables fast deployment and easy repositioning.

Wireless - Wifi and Bluetooth APs and RFID readers are commonly PoE-compatible, to allow remote location away from AC outlets, and relocation following site surveys.

How to upgrade to PoE

Adding PoE to your network is straightforward, and there are two routes you can choose:

A PoE switch is a network switch that has Power over Ethernet injection built-in.  Simply connect other network devices to the switch as normal, and the switch will detect whether they are PoE-compatible and enable power automatically.

PoE switches are available to suit all applications, from low-cost unmanaged edge switches with a few ports, up to complex multi-port rack-mounted units with sophisticated management.



A midspan (or PoE injector) is used to add PoE capability to regular non-PoE network links.  Midspans can be used to upgrade existing LAN installations to PoE, and provide a versatile solution where fewer PoE ports are required.  Upgrading each network connection to PoE is as simple as patching it through the midspan, and as with PoE switches, power injection is controlled and automatic.

Midspans are available as multi-port rack-mounted units or low-cost single-port injectors.

It is also possible to upgrade powered devices, such as IP cameras, to PoE by using a PoE splitter.  The PoE splitter is patched in to the camera's network connection, and taps off the PoE power, which it converts into a lower voltage suitable for the camera.


Want to know more?

To find out about the myths and misconceptions about Power over Ethernet, options for high-power PoE, and a little more about how the technology works, please continue to PoE Explained, Part 2.

Our Power Without the Struggle white paper makes the case for PoE deployment in more detail, and explains how PoE can be used effectively.

We also have a PoE Explained white paper, which describes the functionality of PoE in technical, but straightforward, detail.

Or simply contact Veracity or one of our representatives, to see how we can help you make the most out of your PoE application.


Copyright 2010, Veracity UK Ltd.