Allied Telesis GS950 PS Series, Руководство по установке, Страница: 27 / 108

GS950 PS V2 Series of Gigabit Ethernet PoE+ Switches Installation Guide
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PoE Standards
The GS950 PS V2 Switches support these PoE standards:
 PoE (IEEE 802.3af): This standard provides up to 15.4 watts at the
switch port to support powered devices that require up to 12.95
watts.
 PoE+ (IEEE 802.3at): This standard provides up to 30.0 watts at
the switch port to support powered devices that require up to 25.5
watts.
Powered Device
Classes
Powered devices are grouped into classes, based on their power
requirements. The GS950 PS V2 Switches support the five classes listed
in Table 3.
Note
The switches can support any combination of PoE class devices up
to their maximum PoE power budgets.
PoE Port
Priorities
If the power requirements of the powered devices exceed the switch’s
power budget, the switch will deny power to some ports based on a
system called PoE port priorities. You can use this feature to ensure that
powered devices critical to the operations of your network are given
preferential treatment by the switch in the allocation of power should the
demands of the devices exceed the available power budget.
There are three priority levels:

Critical

High

Low
Ports set to the Critical level, the highest priority level, are guaranteed
power before any of the ports assigned to the other two priority levels.
Ports assigned to the other priority levels receive power only if all the
Table 3. IEEE Powered Device Classes
Class
Maximum Power
Output at the Switch
Port
Powered Device 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