Below is a worst-case example of an 800-Watt power supply (not including power consumed by the switch
itself), powering class-3 PDs. Assume each non-Cisco PD requires 7-Watts to operate and is therefore a
class 3 device in terms of power.
Of the available 800 Watts, only 46 PDs can be powered because 17.3 Watts is reserved for each PD
(800W / 17.3W = 46). The actual power demand is 322 Watts (46 * 7W = 322W). Therefore, 478 Watts is
stranded because each PD has an additional 10.3 Watts reserved but never used (800W – 322W = 478W).
If the class-3 PDs were Cisco phones, CDP would discover them and apply the exact amount of power they
need for operation.
Cisco has addressed this issue with commands like “
power inline allocation”
and others.
Details are in section 7.
Avaya’s PSEs
The next natural question concerns implementation issues using Avaya’s PSEs. Avaya uses best-in-class
methods for all PSE equipment. There are no power transport inefficiencies to consider, no logical
reservation of power, no additional money spent to upgrade power supplies, no unintelligent static allocation
of power and no penalties when using any vendor’s standards compliant PD. Another benefit of dynamic
power allocation is the small number of commands needed to configure and maintain the switch or Mid-
Span. As you will see, there are fewer commands and command options using Avaya PSE products.
All ports can be used on all of Avaya’s PSE equipment – even with the most power hungry Avaya PDs
listed in the table below. This table lists very conservative power consumption numbers for Avaya IP
phones.
Values in the worst case row are not achievable in any customer environment. Values in the typical row are
conservative and the actual power draw may be lower. Using the worst case values will prevent issues
caused by switch configuration and is discussed earlier in this section.
Table 4 Avaya 46xx IP Phone Power Consumption in Watts assuming 48 volts.
Model
Notes
4601/02 4602SW 4606/12/24 4610 4620
Mfg
Disc.
4620SW
< 9/2004
4620SW
>9/2004
4621SW
4622SW
4625SW
PoE Class Class 2
Class 2 Class 0
Class 2 Class 3 Class 3
Class 2 Class 2 Class 3
Typical 3.5 4.1 5.0
4.0 7.7 5.9 4.6 4.9 7.8
Worst
Case
4.6 5.0 6.4 6.0 9.9 8.0
5.75 6.45 9.42
MJK
Copyright ©
2006 Avaya Inc. All Rights Reserved.
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