Allied Telesis AlliedWare Plus AT-GS980M/52, Installation Manual, Page: 27 / 94

GS980M Series Installation Guide
27
Power Budget
The AT-GS980M/52PS Switch has a DC power budget of 740W. This is
the total maximum amount of power that the switch can supply to the
powered devices on its twisted pair ports.
To determine the maximum number of PoE devices the switch can support
at one time, compare their power requirements against its power budget.
The switch can supply power to all devices provided their total power
requirement is less than its power budget. If the total power requirement of
the devices exceed the power budget, the switch will deny power to one or
more ports using port priorities.
The switch can handle different power requirements on different ports.
This enables you to connect different classes of PoE equipment to the
ports on the switch.
Port Priorities
If the switch determines that the power requirements of the powered
devices exceed its power budget, it will deny power to some ports based
on a system called port priorities. You can use this mechanism to ensure
that powered devices critical to the operations of your network are given
preferential treatment by the switch in the distribution of power should the
demands of the devices exceed the available capacity.
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
Critical ports are receiving power. Ports that are connected to your most
critical powered devices should be assigned to this level. If there is not
enough power to support all the ports set to the Critical priority level, power
is provided to the ports based on port number, in ascending order.
The High level is the second highest level. Ports set to this level receive
2 7.0W 3.84W to 6.49W
3 15.4W 6.49W to 12.95W
4 30.0W 12.95W to 25.5W
Table 4. IEEE Powered Device Classes (Continued)
Class
Maximum Power
Output from a Switch
Port
PD Power Range