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Cisco Unified IP Phone 7970G/7971G-GE Administration Guide for Cisco Unified Communications Manager 7.0
OL-15299-01
Chapter 2 Preparing to Install the Cisco Unified IP Phone on Your Network
Providing Power to the Phone
Phone Power Consumption and Display Brightness
The power consumed by a phone depends on its power configuration. See Table 2 -1 for a power
configuration overview. See Table 2-2 for the maximum power consumed by a phone for each
configuration option and the correlating phone screen brightness level.
Note Power consumption values shown in the table include power losses in the cable that connects the phone
to the switch.
Note When a phone is powered with a method that does not support full brightness for the phone screen, the
phone Brightness control (Settings > User Preferences > Brightness) does not allow you to set the
brightness to the maximum value.
Power Outage
Your accessibility to emergency service through the phone is dependent on the phone being powered. If
there is an interruption in the power supply, Service and Emergency Calling Service dialing will not
function until power is restored. In the case of a power failure or disruption, you may need to reset or
reconfigure equipment before using the Service or Emergency Calling Service dialing.
Table 2-2 Power Consumption and Display Brightness for Power Configurations
Phone Model Power Configuration
Max. Power
Consumed from a
Switch
Phone Screen
Brightness
Cisco Unified IP
Phone 7970G
Cisco prestandard PoE from a switch that supports a maximum of 7
W power per port, with bidirectional power negotiation enabled
6.3 W Approx. 1/2
Cisco prestandard PoE from a Cisco Switch that supports 7 W or
15.4 W power per port, without bidirectional power negotiation
6.3 W Approx. 1/2
IEEE 802.3af Class 3 power from a Cisco switch, without
bidirectional power negotiation
6.3 W Approx. 1/2
IEEE 802.3af Class 3 power from a third-party switch 6.3 W Approx. 1/2
IEEE 802.3af Class 3 power from a Cisco switch, with bidirectional
power negotiation enabled
10.25 W Full1
1. Starts at approximately 1/2 brightness, changes to full brightness when the phone negotiates additional power.
Cisco prestandard PoE from a Cisco Switch that supports 15.4 W
power per port, with bidirectional power negotiation enabled
10.25 W Full
External power — Full
Cisco Unified IP
Phone 7971G-GE
IEEE 802.3af Class 3 power from a Cisco switch (with or without
bidirectional power negotiation enabled) or from a third-party
switch
15.4 W Near full
External power — Full