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Chapter 1: Overview
26
PoE Powered
Device Classes
Powered devices are grouped into the five classes listed in Table 6. The
classes are based on the amount of power the devices require. The
switches support all five classes.
PoE Power
Budget
The AT-GS900/8PS switch has a power budget of 75 watts. This is the
maximum amount of power the switch can provide at one time to the
powered devices.
The sum of the power requirements of each of the PoE devices connected
to the switch determines the maximum number of devices that the switch
can support at one time. So long as the total power requirements of the
powered devices is less than the power budget of the switch, the switch
can supply power to all of the devices. But if the total power requirements
exceed the power budget, the switch denies power to one or more ports
using a mechanism referred to as port prioritization.
To determine whether the power requirements of the PoE devices you
plan to connect to the switch exceed its power budget, refer to the
documentation for the power requirement of each device and add the
requirements together. The switch should be able to power all of the
devices simultaneously as long as the total is below its power budget. If
the total exceeds the available power budget, you should consider
reducing the number of PoE devices so that all of the devices receive
power. Otherwise, the switch powers a subset of the devices, based on
port prioritization.
The switch can handle different power requirements on different ports.
This enables you to connect different classes of PoE equipment to the
PoE ports on the switch.
Table 6. IEEE Powered Device Classes
Class
Maximum Power
Output from a Switch
Port
PD Power Range
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 30.0W 12.95W to 25.5W