Allied Telesis AT-8100 Series - Manual (Page 170)

Chapter 15: Power Over Ethernet (PoE)
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Overview
The AT-8100L/8PoE, AT-8100S/24PoE, and AT-8100S/48PoE switches
feature Power over Ethernet (PoE) on the 10/100Base-Tx ports. PoE is
used to supply power to network devices over the same twisted-pair
cables that carry the network traffic.
The main advantage of PoE is that it can make installing a network easier.
The selection of a location for a network device is often limited by whether
there is a power source nearby. This constraint limits equipment
placement or requires the added time and cost of having additional
electrical sources installed. However, with PoE, you can install PoE-
compatible devices wherever they are needed without having to worry
about a nearby power source.
Power Sourcing
Equipment (PSE)
A device that provides PoE to other network devices is referred to as
power sourcing equipment (PSE). The AT-8100L/8PoE, AT-8100S/
24PoE, and AT-8100S/48PoE switches are PSE devices providing DC
power to the network cable and functioning as a central power source for
other network devices.
Powered Device
(PD)
A device that receives power from a PSE device is called a powered
device (PD). Examples include wireless access points, IP phones,
webcams, and even other Ethernet switches.
PD Classes
PDs are grouped into five classes. The classes are based on the amount
of power that PDs require. The AT-8100 PoE switches support all five
classes listed in Table 5.
Power Budget
Power budget is the maximum amount of power that the PoE switch can
provide at one time to the connected PDs.
The AT-8100L/8POE switch has one power supply. The AT-8100S/
24POE and AT-8100S/48POE switches have two power supplies and can
Table 5. IEEE Powered Device Classes
Class
Maximum Power Output
from a Switch Port
Power Ranges of the PDs
0 15.4W 0.44W to 12.95W
1 4.0W 0.44W to 3.84W
2 7.0W 3.84W to 6.49W
3 15.4W 6.49W to 12.95W
4 34.2W 25.5W to 38.9W