Cisco 7971G-GE Administration Guide - Page 43

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. Table 2-2 Power Consumption and Display Brightness for Power Configurations Phone Model Power Configuration Max. Power Consumed from a Phone Screen Switch Brightness Cisco Unified IP Cisco prestandard PoE from a switch that supports a maximum of 7 6.3 W Phone 7970G W power per port, with bidirectional power negotiation enabled Approx. 1/2 Cisco prestandard PoE from a Cisco Switch that supports 7 W or 6.3 W 15.4 W power per port, without bidirectional power negotiation 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 IEEE 802.3af Class 3 power from a Cisco switch, with bidirectional 10.25 W power negotiation enabled Approx. 1/2 Full1 Cisco prestandard PoE from a Cisco Switch that supports 15.4 W 10.25 W Full power per port, with bidirectional power negotiation enabled External power - Full Cisco Unified IP IEEE 802.3af Class 3 power from a Cisco switch (with or without 15.4 W Phone 7971G-GE bidirectional power negotiation enabled) or from a third-party switch Near full External power - Full 1. Starts at approximately 1/2 brightness, changes to full brightness when the phone negotiates additional power. 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. OL-15299-01 Cisco Unified IP Phone 7970G/7971G-GE Administration Guide for Cisco Unified Communications Manager 7.0 2-5