Cisco 7821, Руководство администратора

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Power Reduction
You can reduce the amount of energy that the Cisco IP Phone consumes by using Power Save mode.
Power Save
In Power Save mode, the backlight on the screen is not lit when the phone is not in use. The phone
remains in Power Save mode until the user lifts the handset or presses any button. Set up each phone to
enable or disable Power Save settings.
The Cisco IP Phone 7811 does not support Power Save because the phone screen does not have a backlight. Note
Power Negotiation Over LLDP
The phone and the switch negotiate the power that the phone consumes. Cisco IP Phone operates at multiple
power settings, which lowers power consumption when less power is available.
After a phone reboots, the switch locks to one protocol (CDP or LLDP) for power negotiation. The switch
locks to the first protocol (containing a power Threshold Limit Value [TLV]) that the phone transmits. If the
system administrator disables that protocol on the phone, the phone cannot power up any accessories because
the switch does not respond to power requests in the other protocol.
Cisco recommends that Power Negotiation always be enabled (default) when connecting to a switch that
supports power negotiation.
If Power Negotiation is disabled, the switch may disconnect power to the phone. If the switch does not support
power negotiation, disable the Power Negotiation feature before you power up accessories over PoE. When
the Power Negotiation feature is disabled, the phone can power the accessories up to the maximum that the
IEEE 802.3af-2003 standard allows.
When CDP and Power Negotiation are disabled, the phone can power the accessories up to 15.4W.
Note
Network Protocols
Cisco IP Phones support several industry-standard and Cisco network protocols that are required for voice
communication. The following table provides an overview of the network protocols that the phones support.
Table 5: Supported Network Protocols on the Cisco IP Phone
Usage Notes Purpose Network Protocol
— BootP enables a network device,
such as the Cisco IP Phone, to
discover certain startup
information, such as its IP address. Bootstrap Protocol (BootP)
Cisco IP Phone 7800 Series Multiplatform Phones Administration Guide
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About the Cisco IP Phone
Power Reduction