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Phone power requirements
In this article
Feedback?This Help article is for Cisco Desk Phone 9800 Series and Cisco Video Phone 8875 registered to BroadWorks, Webex Calling, or Unified CM.
Cisco IP Phones consume external power or Power over Ethernet (PoE). A power adapter connects a phone with external power supply. A switch can provide PoE to a phone through the Ethernet cable.
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Power type |
Guidelines |
|---|---|
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External power Provided through the external power adapter |
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PoE power Provided by a switch through the Ethernet cable attached to the phone. |
Cisco IP Phones support 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
- Cisco IP Phones data sheets that include phone power requirements
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Document topics |
URL |
|---|---|
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PoE Solutions |
http://www.cisco.com/c/en/us/solutions/enterprise-networks/power-over-ethernet-solutions/index.html |
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UPoE |
http://www.cisco.com/c/en/us/solutions/enterprise-networks/upoe/index.html |
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Cisco Catalyst Switches | |
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Integrated Service Routers | |
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Cisco IOS Software |
http://www.cisco.com/c/en/us/products/ios-nx-os-software/index.html |
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Cisco Video Phone 8875 Data Sheet | |
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Cisco Desk Phone 9800 Series Data Sheet |
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 Phones consume by using the Office Hours feature. The Office Hours feature lets phones automatically power on, power off, or turn off the display based on a set schedule, helping organizations save energy, reduce costs, and optimize device performance.
Three power-saving options are available on the phone to reduce power consumption during periods of inactivity.
Display Off Mode
When the Office Hours feature is enabled, Cisco Desk Phone 9841, 9851, 9861, and 9871 and Cisco Video Phone 8875 turn off the backlight according to the configured schedule. You can light up the display or backlight by pressing any key on the phone.
Deep Sleep Mode
In the Deep Sleep Mode, Cisco IP Phones automatically power down during the designated periods. You can choose to enable Deep Sleep Mode exclusively for non-workdays, or for both non-workdays and non-working hours on workdays. The phones automatically wake up according to the configuration on the call control system. Alternatively, you can manually wake up the phone by pressing the Select button on the Navigation Cluster on Cisco Desk Phone 9841, 9851, and 9861 or tapping the Home button on Cisco Desk Phone 9871.
Smart Power
The Smart Power feature reqiures that Cisco IP Phones use Power over Ethernet (PoE) as the power source. You can use the Smart Power feature to allow Cisco Smart Switches to wake up the phones from Deep Sleep following the configuration on the call control system. Additionally, you can choose to let a switch manage the phone's Display Off and Deep Sleep modes modes based on the schedules configured on the switch.
On Cisco Desk Phone 9811 and Cisco Video Phone 8875, Deep Sleep Mode can only be enabled by Cisco switches through the Smart Power feature. The phones automatically wake up according to the configuration on the switch. Alternatively, you can manually wake up the phone by pressing the Select button on the Navigation Cluster on Cisco Desk Phone 9811 or pressing the Power button on Cisco Video Phone 8875.
For more information, see the following articles.
Power negotiation over LLDP
The phone and the switch negotiate the power that the phone consumes. Cisco IP Phones operate 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.
