PoE - Power over Ethernet Primer

What is Power over Ethernet ?

Power over Ethernet, commonly abbreviated to PoE, is a technology that enables DC power to be delivered over the same twisted pair copper cabling as the data. This allows end devices such as IP phones, CCTV cameras and wireless access points to receive power across the network and avoids the need to install electrical cabling and a power source at the remote end.

Power over Ethernet basics

PoE standards and terminology

PoE is standards based to ensure interoperability between those devices providing power, power sourcing equipment (PSE) and those devices receiving it, powered devices (PD).

Any device that can received power via its Ethernet interface can be described as a 'powered device', PD.

Equipment that provides Power over Ethernet is described as 'power sourcing equipment', PSE. These are generally Ethernet switches with PoE capability but can also be PoE capable media converters or injectors.

PoE standards have developed over time to provide increased power to end devices. The latest standard can provide up to 100W of power to the end device.

Common Name IEEE Standard Power at PD Max Power from Port
PoE, 2 Pair PoE 802.3af 15.4W 12.95W
PoE+, PoE Plus 802.3at 30W 25.5W
PoE++, Ultra PoE 802.3bt (Type 3) 60W 51W
High-power PoE 802.3bt (Type 4) 100W 71.3W

The most pertinent column is the 'power at PD'. This tells us which standard the PSE must comply with in order to provide enough power for the PD.

Why use Power over Ethernet ?

Ease of deployment

PoE allows for simple deployment of powered devices to any location where a copper network point exists. This removes the reliance on traditional power being close by and available. The flexibility PoE can bring means end devices and therefore operational services can be rolled out faster and easier.

Ease of installation

IEEE compliant PoE is safe, typically voltages are less than 60V DC. Even if non PoE devices are connected to a IEEE PoE outlet no damage will occur as power is only supplied after the PD has confirmed its power requirements with the PSE. New network installations can be realised without the need to employ the services of an electrician to install dedicated electrical cables. This makes installations faster and reduces the risks associated with electrical work significantly reducing the cost of installation.

Availability / Reliability

A PoE installation is commonly backed up by a UPS ensuring continued operation. PoE switches often have advanced management facilities to automatically monitor end devices. These watchdog functions power cycle end devices should they become unresponsive, reducing downtime and maintaining availability.

How to add PoE to your network

Adding PoE capability to your network is a simple process. Generally power is provided by using 1 of 2 methods.

The first method is a Power over Ethernet switch. These can be used to implement not only network functions but also to provide power to end devices. Depending on the complexity of the switch, differing features may be available. An unmanaged PoE switch simply provides data and power. A managed PoE switch adds management features that allows configuration and monitoring of PoE functions. An industrial PoE switch adds the above but in a temperature hardened package that may be required in harsh environments.

PoE IP phone

he second method is by using a Power over Ethernet injector. This takes a non PoE interface and adds PoE to it. This provides a simple way to add PoE to your network whilst preserving investment in switching equipment. The PoE injector may take the form of a media converter, converting fibre optic interfaces to a copper one whilst also adding PoE capability.

PoE power over Ethernet injector

Summary

PoE facilitates the integration of an ever increasing list of end devices. PoE provides a cost effective simple way to provide power to these device without the need and expense of installing additional dedicated power systems.

Lanode have wide range of PoE equipment.

Unmanaged PoE Switches...

Managed PoE Switches...

Industrial PoE Switches...

PoE Media Converters...

 

If you need help with your PoE application call us, we'd be happy to help in any way we can.