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Understanding Power over Ethernet

Posted by The UC Buyer

Aug 20, 2019

Power over Ethernet, or PoE, describes a system that passes electrical current along twisted pair wiring, like that which is found within ethernet cables. The amount of electricity necessary to power a UC device is relatively small, well under 60 volts (whereas a standard AC outlet provides twice this amount). The router itself must send out the voltage, which is something to consider if you have to upgrade the LAN equipment anyway.

PoE routers are more expensive than unpowered ones, so understanding how they work and what they can offer will be important to justify the price.

poe_power_ethernet

What Types of Devices Can Be PoE?

The most common device to Power over Ethernet is IP phones, but IP cameras, wireless access points, and other types of network devices can be attached. Most devices that are Power over Ethernet enabled also have an option for power to be delivered via more traditional 120v plug. 

 

Why Would I Use Power over Ethernet?

PoE must be sent out from the router and typically end if the ethernet line hits another hub or splitter, unless the hub is a powered midspan device (one that injects power into the line, much like the router has). To work properly, the device must connect directly to the powering router. If your device is PoE capable and the ethernet delivering the signal is providing power, you only have to attach the Ethernet cable to power your device. The same cable that delivers the network signal also powers the device, without the need to attach a power brick or AC adapter.

If you can power an IP Phone or other device with a single cable, it frees up the design from also requiring a power block and AC source. This makes for a less invasive and faster install overall. If you daisy chain a desktop computer through the IP desk phone, PoE will function normally for the phone while the network signal penetrates to the next leg (the computer).

Another great application scenario for PoE is for demo kits. If you can eliminate the need to carry around power supplies and know you will have your own PoE enabled switch, you can make the demo appear to be elegant and clean. The demo can be set up and torn down faster, takes less space in whatever container you need to use for transportation, and reduces clutter.

 

When Would I Not Want to Use Power over Ethernet?

While PoE is great, clean, and modern, there may be places where it is not practical. For example, if you must run more than 100 meters of Ethernet cable from your original PoE source to the endpoint, you will need to have some kind of range extender. The cost to have a Power over Ethernet range extender adds to the expense over a regular hub or other method to extend the signal of the data itself. 

Furthermore, being a low voltage signal, it degrades over distance; while the data may reach to the full 100 meters, for devices more complex than a small camera, there might not be enough juice at the end to provide consistent, reliable power for the appliance itself.



Power over Ethernet is a great way to have networked hardware that uses low amounts of power to operate installed without extra power adapters, but there are limits. The PoE network equipment is more costly and for very long runs of cable this becomes compounded. But if you have to upgrade your network equipment anyway, it might just be worth your consideration.

Topics: Technology, Telephony, Digital Transformation, Customer Journey

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