Power Over Ethernet (POE) and POE Injectors

This article describes what is POE – Power Over Ethernet, how it helps transmit power along with data, what are POE Injectors, what are the types of POE Injectors, what a POE Injector management software does and some devices that support POE.

What is POE and why is it required?

Power Over Ethernet. That’s the expansion. You would have noticed a lot of devices connected to the IP Network Switches like Wireless Access Points, IP Phones etc. are not powered by a separate AC/DC source. Well, where do they get their power from? No, wireless power has not been discovered yet!

Power Over Ethernet (Specified by IEEE 802.3af and 802.3at Standards) enables electrical power to be carried along with data in the network cables (Cat x type) so that these devices need not be separately powered through a power source. It helps as devices like Access Points and IP Cameras are kept mostly at inaccessible places and carrying a power cable/adaptor may not be feasible and might increase the cost.

The Power Over Ethernet can be directly provided by IP Network Switches (Some switches are fully POE enabled on all the ports, while others have a few ports that can support POE) or it can be provided by POE Injectors, if the network switches are not POE enabled.

Single Port POE Injector:

A Single port POE Injector has two RJ-45 connections besides a power connectivity. This can selectively power one POE enabled device that is connected to it. There is a Cat x cable running from the switch to one of the POE injector ports and another long cable goes out from the next port (Carrying both power and data) to the network device that needs to be powered. POE Injector is kept close to the network switch so that it can utilize the power from the racks, UPS etc. Yes, POE Injector needs to be powered through AC/DC source!

Single port POE Injectors come with a standard 10/100 Mbps version and 10/100/1000 Mbps version to support 1GE Networks. They provide a maximum of 15.4W (approximately) and support IEEE 802.3af standards. Well, both the Power Over Ethernet Injector and the network device powered by it needs to support this standard. In situations like a single wireless access point being required for a conference room, there is no need buy a POE Enabled Switch on all ports!

High Power Applications:

There are certain devices like PTZ Camera, IEEE 802.11n access points etc. which needs a higher power (In the range of 30-40W or 60W) which cannot be given by the normal POE Injector. So, for such cases, there are special POE Injectors that need to be bought.

Multiple Port POE Injector:

Suppose, there is a 24 Port Switch (Without POE Capability) and you want all the 24 Ports to support devices with POE. You can either change the switch and buy a POE enabled Switch or buy a multiple port POE Injector. Well, this also looks like a switch! But instead of 24 ports, it has 48 Ports and a control port. So, each port of the switch is connected to one port of this multi-port POE Injector and each network device that needs to be powered is also connected to this multi-port POE Injector.

Management options for POE Injectors:

These POE Injector switches generally support SNMP v3, so you can manage them as a part of your Network Management Software (NMS) that supports SNMP v3. Or, certain POE Injector vendors offer a management software for these POE Injectors (Especially multi-port POE Injectors) that can do the following:

¤ Status display of each POE port.
¤ Activation/ Deactivation of POE per port that can be automatically scheduled (say switched off during weekends etc).
¤ Limit maximum power per port (For lower powered devices). Actually, the POE Injectors can do this themselves too.
¤ Give priority for each port, so that only the higher priority ports would be working when the power is down and the rest are automatically switched off.
¤ Enable SNMP Traps to notify you when any POE Ports are down.
And a lot more management features like Radius Integration, etc!!  Talk about being proactive!

Some devices that support POE: Wi-Fi Access points, Wi-Max Access Points, IP Cameras, RFID Access Points, thin clients, IP Phones, IP Video Phones, etc.

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