Allied Telesis AT-FS970M Series - Manual (Page 170)

Chapter 15: Power Over Ethernet (PoE)
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Overview
The AT-FS970M/8PS, AT-FS970M/8PS-E, AT-FS970M/24PS, and AT-
FS970M/48PS 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-FS970M/8PS, AT-FS970M/
8PS-E, AT-FS970M/24PS, and AT-FS970M/48PS 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-FS970M 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-FS970M/8PS and AT-FS970M/8PS-E switches have one power
supply. The AT-FS970M/24PS and AT-FS970M/48PS switches have two
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