HP ProCurve 3500-24 User Manual

The IEEE 802.3af standard requires power sourcing equipment (PSE) to choose between the options. It is not
possible to mix and match or to use all pairs for power transmission. HP ProCurve switches provide power over
the data pairs. However, the standard requires PDs to be able to accept power over either data pairs or unused
pairs.
PoE negotiation
In most networks, PSE will be connected to some devices that support PoE and some that do not. Consequently,
in order to prevent damage to non-PoE devices, the IEEE 802.3af specification includes a negotiation
mechanism between PSEs and the stations connected to them. Under the specification, PSEs apply a slight
voltage on the power-delivery pairs. If there is a valid PD on the cable, it will present a resistance and a
capacitance.
Typically, this discovery process requires approximately 500 milliseconds. The PSE will apply the full wattage
if it discovers a PD, but the flow is current-limited to prevent damage to cable and equipment under fault
conditions.
After discovery, a PD must draw a minimum current for the power flow to remain active. If, for example, the PD
is unplugged, the PSE will discontinue power supply over the cable. The discovery process will be repeated
when the PD is returned to service.
The HP ProCurve switches described in this document that are PoE-enabled are:
•HPProCurveSwitch5406zl—supportsupto144PoEports
•HPProCurveSwitch5412zl—supportsupto288PoEports
•HPProCurveSwitch3500yl-24G-PWR—supportsupto24PoEports
•HPProCurveSwitch3500yl-48G-PWR—supportsupto48PoEports
•HPProCurve3500-24-PoESwitch—supportsupto24PoEports
•HPProCurve3500-48-PoESwitch—supportsupto48PoEports
Additional PoE power—external supplies
The HP ProCurve 620 Redundant/External Power Supply can be used with up to two 3500 series switches as
an external supply providing an extra 398 W of PoE power for each switch. This extra power can be used to
provide full PoE power redundancy at 15.4 W for all ports for the 3500yl-24G-PWR and 3500-24-PoE. It can
also be used to provide full 15.4 W to all 48 ports on the 3500yl-48G-PWR and 3500-48-PoE, or full PoE
power redundancy at 15.4 W for 24 ports on the 48-port switch.
The HP ProCurve Switch zl Power Supply Shelf provides a 3U-high enclosure to hold up to two extra zl switch
power supplies to provide additional PoE power to zl switches beyond the PoE power available through the
switch’s internal power supplies alone. These extra supplies can also be used to provide PoE power redundancy
beyond what is possible with switch internal supplies. Large Switch zl VoIP installations are ideal environments
for the HP ProCurve Switch zl Power Supply Shelf.
Support for pre-802.3af standard powered devices
The HP ProCurve Switch 5400zl and 3500 series also support a number of pre-802.3af standard powered
devices. These include:
•Cisco7902G,7905G,7912G,7940G,7960GIPPhones
•CiscoAironet350,1100,1200,1230AGAccessPoints
The Cisco pre-802.3af standard IP phones require the use of a straight-through cable for connectivity to
the PSE. These IP phones are dependent on the polarity of the DC voltage (a violation of the IEEE 802.3af
standard) and will not work properly if the data pairs (wires 1 and 2, and 3 and 6) are crossed over anywhere
in the cable plant between the IP phone and power sourcing equipment.
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HP ProCurve 3500-24 Specifications

General

Brand	HP
Model	ProCurve 3500-24
Category	Switch
Language	English