POE Requirements

Unanswered Question

I am very close to the limit on my UPS. The documentation for 7945 and 65 phones states that they will draw a maximum of 12 watts. Is there any info for when this occurs? does an idle phone draw the full 12 watts? Is it safe to figure actual draw as total watts/input voltage (110/220) to get the current (Amps) draw for a given configuration?

I have this problem too.
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Paolo Bevilacqua Sun, 02/03/2008 - 06:50

Hi, the switch will tell you the power supplied to phones. However that doesn't include what the switch uses "for itself".

So the only solution is either design the power system to support the maximum stated draw, or use a clamp ammeter to measure the actual one.

rob.huffman Mon, 02/04/2008 - 11:05

Hi Larry,

Just to add a note;


Q. Do the Cisco Unified IP Phone 7965G and 7945G models support Cisco inline power?

A. No. The phones support only IEEE 802.3af PoE (Class 3).

Q. As Class 3 IEEE devices, do these phones require a continuous draw of 15.4 watts (W) (standard Class 3 allocation)?

A. No. When Cisco Unified IP phones are connected to common switches such as the Cisco Catalyst® 3560 Series Switches or Cisco Catalyst 3570 Switches, the switch can automatically detect the phone type and provide the exact amount of power that the phone needs. The use of Cisco Discovery Protocol provides this greater granularity to the power classification, allowing for more accurate reporting of power consumption, and a higher density of phones on the switch. The Cisco Unified IP Phone 7965G and 7945G models will draw a maximum of 12W from a switch; this places them beyond the limits of Class 2, but below the default 15.4W value of Class 3.

Q. Is there a recommended powering option for these phones?

A. No. Powering decisions depend on the customer's environment. The IEEE 802.3af inline power method can be used; alternatively, either the standard Cisco Unified IP Phone external power adapter or the Cisco Unified IP Phone Power Injector can be used for local power.


Hope this helps!


Jaime Valencia Mon, 02/04/2008 - 11:08

i just looked at all the info we have available for the new phone models but i can't find that information on those new models, sorry

maybe in the future it will be available


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