Power Over Ethernet (PoE)

Power over Ethernet (PoE) is a very convenient method of powering wireless access points (and other network equipment) by capitalising on the flexibility and safety of Cat5e/Cat6 data cable. 

PoE compliant devices are wired to enable them to be powered via their data port; avoiding the need for mains cabling or external power supplies which would otherwise complicate or clutter the installation. The current is very low and the voltage just 48v DC.  Thus, the system is inherently safe and avoids the need for stringent health and safety compliance - making it particularly suitable for use in schools and other public buildings.

When planning a PoE requirement, its important to understand that modern dual radio 'N' access points will require more power than single radio 'G' devices. Care must be taken to ensure the PoE system can deliver the correct levels of power for the device. There are two standards;

• 802.3af - for devices requiring up to 12.4watts 

• 802.3at - for devices requiring up to 25watts

There are three methods of providing PoE to access points and other compliant devices;

1) PoE Injector

An 'injector' is a small, cigarette box sized adaptor that enables powering of an access point from a local mains outlet. There are two inputs - 240vAC mains and RJ-45 data, and one combined RJ-45 power and data outlet. 

Considerations : When powering gigabit (Gbit) access points, ensure the use a gigabit capable injector. Many injectors are only 100Mbit and thus would choke the network performance of the AP.

Best suited to : Rapid, temporary deployment or small installations.

2) PoE Midspan

Great for retro fit to existing infrastructure

3) PoE Switch

Where space is a premium. Most costly option