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Chapter 1: Overview
44
Power Classes Once a PD is discovered, a PSE may optionally perform PD classification
by applying a DC voltage to the port. If the PD supports optional power
classification it will apply a load to the line to indicate to the PSE the
classification the device requires.
Since PDs may require differing power ranges, the IEEE 802.3af and
IEEE 802.3at Power Ethernet standards classifies PDs according to their
power consumption. By providing the PSE with its power range, the PD
allows the PSE to supply power with greater efficiency. The power classes
as outlined by IEEE 802.3af and IEEE 802.3at are as follows showing the
different PD classes and the PSE power output for each corresponding
PD power range:
*
The Maximum Power Level Output levels reflect the loss introduced by a 100
meter Ethernet cable between the Power Source Equipment (PSE) and the
Power Device (PD).
A port connected to a network node that is not a powered device functions
as a regular Ethernet port, without PoE. The PoE feature remains enabled
on the port but no power is delivered to the device.
Note
The PoE/PoE+ power supplied from ports 21R, 22R, 23R and 24R is
unaffected by insertion of an SFP module in to the corresponding
SFP combo port.
Power Capacity The PSU in the x600-24Ts-POE supplies enough power for the switch
itself and for PoE provision for all PoE capable switch ports. However, the
PSU in the x600-24Ts-POE+ supplies enough power for the switch itself
and enough power is available for PoE+ provision for 12 of the 24 PoE+
capable switch ports. Enhanced PoE (20W per port) can be configured to
18 PoE ports on the x600-24Ts-PoE.
The maximum possible PoE power requirement (24 ports x 15.4W ~
370W) falls below the maximum amount of power available (370W) for the
Table 9. Class vs. Power Levels
PD Class
Maximum Power Level
Output at the PD
*
Maximum Power Level
Output at the PSE
0 0.44W to 12.95W 15.4W
1 0.44W to 3.84W 4.0W
2 3.84W to 6.49W 7.0W
3 6.49W to 12.95W 15.4W
4 12.95W to 25.5W 30W