1. Introduction and Overview
The Cisco IP Phone 6851 with Multiplatform Firmware is designed to provide high-fidelity voice communications. This IP phone is suitable for mid-sized to large enterprise environments transitioning to an IP Communications system. It features a 3.5-inch grayscale display and supports Class 2 Power over Ethernet (PoE) and up to 4 SIP registrations.

Image 1.1: Cisco IP Phone 6851. This image displays the main unit of the Cisco IP Phone 6851, including the handset, keypad, navigation buttons, and the 3.5-inch grayscale display. The screen shows an incoming call notification.
2. Package Contents
Verify that your package contains the following items:
- Cisco IP Phone 6851 unit
- Handset
- Handset cord
- Ethernet cable
- North American Power Adapter (if not using Power over Ethernet)
- Quick Start Guide (not included in this digital manual)
3. Setup Instructions
3.1 Connecting the Phone
- Connect the Handset: Plug one end of the handset cord into the handset and the other end into the handset port on the phone base.
- Connect to Network (PoE): If using Power over Ethernet (PoE), connect one end of the Ethernet cable to the network port on the phone and the other end to a PoE-enabled network switch or router. The phone will power on automatically.
- Connect to Network (Power Adapter): If not using PoE, connect the power adapter to the phone's power port and then plug the adapter into a standard electrical outlet. Then, connect one end of the Ethernet cable to the network port on the phone and the other end to a network switch or router.
- Connect to PC (Optional): If you wish to connect a PC through the phone, connect an Ethernet cable from the PC port on the phone to your computer's Ethernet port.
3.2 Initial Configuration
Upon initial power-up, the phone will attempt to connect to your network and register with your IP telephony system. This process may take a few minutes. Follow any on-screen prompts or consult your system administrator for specific network configuration details.
4. Operating Instructions
4.1 Basic Call Functions
- Making a Call:
- Lift the handset or press the Speaker button.
- Dial the desired number using the keypad.
- Press the Call softkey or wait for the call to connect automatically.
- Answering a Call:
- Lift the handset, or press the Answer softkey, or press the Speaker button.
- Ending a Call:
- Replace the handset, or press the End Call softkey, or press the Speaker button again.
- Redial: Press the Redial softkey to call the last dialed number.
4.2 Advanced Features
- Hold: During an active call, press the Hold button. Press it again to resume the call.
- Mute: Press the Mute button to mute your microphone. Press it again to unmute.
- Speakerphone: Press the Speaker button to use the speakerphone.
- Headset: Connect a compatible headset to the headset port. Press the Headset button to use the headset.
- Volume Adjustment: Use the Volume rocker button to adjust the volume of the handset, speakerphone, or headset during a call, or the ringer volume when idle.
- Conference Calls: The phone supports 2-way conference calls.
- During an active call, press the Conference softkey.
- Dial the number of the third party.
- Once the third party answers, press the Conference softkey again to join all parties.
- Voicemail: Press the Messages button to access your voicemail. Follow the audio prompts.
5. Maintenance
To ensure the longevity and optimal performance of your Cisco IP Phone 6851, follow these maintenance guidelines:
- Cleaning: Use a soft, lint-free cloth slightly dampened with water to clean the phone's exterior. Avoid using harsh chemicals, abrasive cleaners, or solvents, as these can damage the finish and electronic components.
- Display Care: Gently wipe the display with a soft, dry cloth. Do not press hard on the screen.
- Environment: Keep the phone in a dry environment, away from direct sunlight, excessive heat, and moisture.
- Cables: Ensure all cables are securely connected and not kinked or damaged.
6. Troubleshooting
This section provides solutions to common issues you might encounter with your IP Phone.
| Issue | Possible Cause | Solution |
|---|---|---|
| Phone does not power on. | No power from PoE or power adapter. |
|
| Cannot make or receive calls. | Network connectivity issue or registration failure. |
|
| No dial tone. | Phone not registered or handset/speaker issue. |
|
| Poor audio quality. | Network congestion or faulty equipment. |
|
7. Specifications
| Brand | Cisco |
| Model Number | 6851 (CP-6851-3PW-NA-K9=) |
| Display | 3.5-inch Grayscale |
| Power Source | Power Adapter / Class 2 PoE (Power over Ethernet) |
| SIP Registrations | Up to 4 |
| Telephone Type | Corded IP Phone |
| Dialer Type | Single Keypad |
| Answering System Type | Digital |
| Compatible Devices | VoIP services, PSTN, compatible communication devices |
| Conference Call Capability | 2-way |
| Item Weight | 1.36 pounds (approx. 0.62 kg) |
| Product Dimensions (L x W x H) | 14.85 x 9.1 x 2.95 inches (approx. 37.7 x 23.1 x 7.5 cm) |
| Color | Charcoal |
| Country of Origin | China |
8. Warranty and Support
8.1 Limited Hardware Warranty
The Cisco IP Phone 6851 comes with a 1-Year Limited Hardware Warranty. This warranty covers defects in materials and workmanship under normal use. For specific terms and conditions, please refer to the official Cisco warranty documentation or contact Cisco support.
8.2 Technical Support
For technical assistance, troubleshooting beyond this manual, or warranty claims, please contact your IT department or authorized Cisco support provider. You may also visit the official Cisco support website for additional resources and contact information.
Cisco Support Website: www.cisco.com/support





