Poe (Power Over Ethernet) Settings - HP nj2000 User Manual

PoE (Power over Ethernet) Settings

The switch can provide DC power to a wide range of connected devices, eliminating the
need for an additional power source and cutting down on the amount of cables attached to
each device. Once configured to supply power, an automatic detection process is initialized
by the switch that is authenticated by a PoE signature from the connected device. Detection
and authentication prevent damage to non-802.3af compliant devices.
The switch's power management enables total switch power and individual port power to be
controlled within the switch power budget. PSE ethernet ports 1 and 2 are capable of
delivering 802.3af PoE. Port power can be automatically turned on and off for connected
devices, and a per-class power priority can be set so that the switch never exceeds its power
budget. When a device is connected to a switch port, its power requirements are detected
and classified by the switch before power is supplied. If the power required by a device
exceeds the power budget of the port or the whole switch, power is not supplied.
The power source for the NJ2000 determines if PSE ethernet ports 1 and 2 can be used as
802.3af ports. If the NJ2000 uplink port (PD) is connected to a high-power midspan 802.3at
POE device or the external 48VDC power adapter is being used, PSE ethernet ports 1 and 2
can be used as 802.3af ports, 15.4W power budget. If power is provided to the NJ2000 thru
the uplink port connected to a regular 802.3af PoE, then Ethernet ports 1 and 2 cannot be
used as 802.3af ports.
PSE ethernet ports 1 and 2 can be configured to one of two power priority levels, high and
low. To control the power supply within the switch's budget, ports set at high priority have
power enabled in preference to those ports set at low priority with the same PD class. For
example, when a device is connected to a port set to high priority, the switch supplies the
required power, if necessary by dropping power to ports set for a lower priority. If power is
dropped to some low-priority ports and later the power demands on the switch fall back
within its budget, the dropped power is automatically restored.
Copyright © 2009 3Com Corporation. All Rights Reserved.
3Com Network Jack NJ2000
Page 42 of 44