The Cisco IP Phone can be powered with external power or with Power over Ethernet (PoE). A separate power supply provides external power. The switch can provide PoE through the phone Ethernet cable.

Cisco Video Phone 8875 is PoE Class 4 device and requires a switch or line card with Class 4 capabilities to support extra features.

For more information on your phone's power requirements, consult your phone's data sheet.

When you install a phone that is powered with external power, connect the power supply before you connect the Ethernet cable to the phone. When you remove a phone that is powered with external power, disconnect the Ethernet cable from the phone before you disconnect the power supply.

Table 1. Guidelines for Cisco IP Phone Power

Power type

Guidelines

External power: Provided through the CP-PWR-CUBE-4= external power supply

The Cisco Video Phone uses the CP-PWR-CUBE-4 power supply.

PoE power—Provided by a switch through the Ethernet cable attached to the phone.

Cisco Video Phone 8875 supports 802.3af and 802.3at PoE for accessory use. For more information, consult your phone's data sheet.

The switch requires a backup power supply for uninterruptible operation of the phone

Make sure that the CatOS or IOS version that runs on your switch supports your intended phone deployment. See the documentation for your switch for operating system version information.

The documents in the following table provide more information on the following topics:

  • Cisco switches that work with Cisco IP Phones
  • Cisco IOS releases that support bidirectional power negotiation
  • Other requirements and restrictions about power
Table 2. Additional Information

Document topics

URL

PoE Solutions

http://www.cisco.com/c/en/us/solutions/enterprise-networks/power-over-ethernet-solutions/index.html

UPoE

http://www.cisco.com/c/en/us/solutions/enterprise-networks/upoe/index.html

Cisco Catalyst Switches

http://www.cisco.com/c/en/us/products/switches/index.html

Integrated Service Routers

http://www.cisco.com/c/en/us/products/routers/index.html

Cisco IOS Software

http://www.cisco.com/c/en/us/products/ios-nx-os-software/index.html

Power outage

Your access to emergency service through the phone requires that the phone receive power. If a power interruption occurs, service or emergency calling service dialing does not function until power is restored. If a power failure or disruption occurs, you may need to reset or reconfigure the equipment before you can use service or emergency calling service dialing.

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 for the scheduled duration or until the user lifts the handset or presses any button.

Power negotiation over LLDP

The phone and the switch negotiate the power that the phone consumes. Cisco Video 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.