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ID #1047

What is power over Ethernet (PoE)?

PoE stands for Power over Ethernet
PoE allows you to supply power to a networking device using the same cable that transmits the data.

PoE's main advantages are:
Lower Cost: PoE eliminates the need for running both data and power wires.
More Flexible: Network devices can be installed and re-located, without concern of an existing AC outlet.
More Reliable: A centralized power source for all devices protected by a UPS distributes power even if the AC electrical power is down.

PoE eliminates the need to install power supplies and AC power outlets.
Power delivery
- up to 15 watts with the existing IEEE802.3af standard
- more than 30 watts with the IEEE802.3at standard

Common products powered via PoE:
- IP Phones
- Wireless Access Points
- Network Cameras

There are two types of PoE products:
- PSE devices
- PD equipment

PSE - Power Sourcing Equipment
Power sourcing equipment (PSE) is a device such as a switch that provides ("sources") power on the Ethernet cable. The maximum allowed continuous output power per cable in IEEE 802.3af is 15.40�W. A later specification, IEEE 802.3at, offers 25.50 W and more.
When the device is a switch, it's called an endspan. Otherwise, if it's an intermediary device between a non PoE capable switch and a PoE device, it's called a midspan.

Powered device
A powered device (PD) is a device powered by a PSE and thus consumes energy. Examples include wireless access points, IP Phones, and IP cameras.

Many powered devices have an auxiliary power connector for an optional, external, power supply. Depending on the PD design, some, none, or all power can be supplied from the auxiliary port, with the auxiliary port sometimes acting as backup power in case of PoE supplied power failure.


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Tags: PoE, Power over Ethernet

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