Before enabling port power, this unit generates a signal that a power-ready device will loop
back. This signal is transmitted on the 7/8 pair and if this is looped back on the 4/5 pair, the
hub then assumes a power-ready device is connected and enables power on that port. The
hub continuously probes the port with signals to ensure the device is still connected. When the
hub no longer detects the looped-back probing signal, it assumes the terminal device has been
disconnected and disables power to that port.
The Catalyst 3524, 3550, 4000 and 6000 series products provide 48 VDC on the data pairs
(1/2 and 3/6).
Before applying this voltage on its port, the Cisco hub first ensures that the attached device is
capable of accepting power. It does this by transmitting a Fast Link Pulse (FLP) on one data
pair while monitoring the second data pair. A power-ready device will loop back this signal to
the hub via the second data pair. Once the hub senses this return signal, it ramps up voltage
on the port.
Once enabled, the port continues to provide power as long as the link signal from the terminal
device is present. When the signal disappears, the port interprets it as a disconnection of the
terminal device and disables power to that port.
HP ProCurve Products
The following brief descriptions cover the HP ProCurve product used to build a VoIP solution.
More detailed information can be found at the HP ProCurve Support web site,
http://www.hp.com/go/hpprocurve. HP ProCurve 2600-PWR series and 5300 series switches
can provide power to IP telephone handsets over standard CAT 5 Ethernet cable via the IEEE
802.3af Power-over-Ethernet (PoE) Standard.
HP ProCurve 5300 with Expandable 10/100 PoE Modules
• Layer 2, 3, and 4 managed chassis
• 5304 provides up to 96 ports (10/100) at 15.4 W PoE
Table 80: HP ProCurve Switches
Switch Series 802.3af PoE
2500 no
2600 yes
2700 no
2800 no
4000m no
4100gl no
6100 no
5300xl yes
9300m no
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