Cisco Phone 8851 Manual

The Cisco IP Phone 8851 is a high-quality, full-featured business IP phone designed for desk workers. It features a high-resolution grayscale display, support for up to 10 lines, integrated Gigabit Ethernet, Power over Ethernet (PoE), advanced audio capabilities, and a wide range of telephony features including hold, transfer, conference, and voicemail access. This manual covers key sections for safety, features, installation, setup, operation, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting Devices 7. Using Phone Features 8. Accessibility Features 9. Care & Cleaning 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: High-resolution grayscale display, Handset, Speakerphone, Line keys, Navigation cluster, Softkeys, Volume rocker, Headset port, Ethernet ports.

Feature	Description
Display	High-resolution grayscale display with adjustable contrast
Line/Feature Keys	Up to 10 programmable line or feature keys
Speakerphone	Full-duplex speakerphone for hands-free calls
Headset Port	3.5mm port for wired headset connection
Network Ports	10/100/1000 SW (to switch) and PC (to computer) Ethernet ports
Power	IEEE 802.3af PoE or optional external power adapter
Audio Codecs	Support for G.711, G.722, G.729a, iLBC
Security	802.1X authentication, signed firmware, secure boot
Hold/Resume	Place calls on hold and resume with a single button
Conference	Establish multi-party conference calls

Installation

Unpack and inspect contents. Place phone on stable surface.

Connect to Network: Use Ethernet cable to connect the SW port to your network switch.
Connect PC (Optional): Use second Ethernet cable to connect PC port to your computer.
Connect Handset: Plug coiled handset cord into handset port.
Connect Headset (Optional): Plug wired headset into 3.5mm headset port.
Apply Power: Phone will power via PoE from switch. If not using PoE, connect the optional power adapter.

WARNING! Use only approved power sources. Ensure cables are not pinched or damaged.

First-Time Setup

Phone will boot and attempt to register with the call control system (e.g., Cisco Unified Communications Manager).

Network Registration: Ensure phone obtains an IP address via DHCP. Check display for registration status.
Configure Extension/Line: Lines are typically provisioned by your system administrator.
Set Preferences: Press the Settings button to adjust ringtone, display contrast, date/time format.
Test Audio: Make a test call to verify handset, speakerphone, and headset audio.

CAUTION! Do not attempt to disassemble the phone. Refer servicing to qualified personnel.

Specifications

Model: Cisco IP Phone 8851.
Display: High-resolution grayscale, adjustable contrast.
Network: Dual 10/100/1000 Mbps Ethernet ports with IEEE 802.3af PoE.
Audio: Wideband audio support (G.722), built-in speakerphone, handset, headset interface.
Protocols: SIP (Session Initiation Protocol) or SCCP (Skinny Client Control Protocol).
Security: 802.1X, TLS, SRTP.

Power Source: IEEE 802.3af PoE (Class 2) or 12V DC external power adapter.

Operating Temp: 32°F to 104°F (0°C to 40°C).

Compliance: FCC Part 15, ICES-003, RoHS, WEEE.

Controls and Settings

Access phone settings via the Settings button. Front Panel: Handset, Speakerphone key, Mute key, Headset key, Volume rocker, Navigation cluster (Up/Down/Left/Right/Select), Softkeys, Line keys.

Key Functions: Hold, Transfer, Conference, Messages, Directory, Settings, Applications, Headset, Speakerphone, Mute.

Settings Menu: User Preferences (Ringtone, Display Contrast), Network Configuration (view IP address), Device Information (model, firmware), Status (line status, missed calls).

Connecting Devices

Network: SW port to switch. PC: PC port to computer. Headset: 3.5mm jack. Power: PoE or external adapter.

Ensure phone and network switch are powered off before connecting cables.

Use standard CAT5e or higher Ethernet cables.

For headset use, plug in before starting a call and press the Headset key.

Tip: Label cables for easier identification during maintenance.

Using Phone Features

Supports standard telephony features and programmable functions.

Make a Call: Lift handset or press Speakerphone/Headset, dial number, press Dial softkey or #.

Answer a Call: Lift handset, press Speakerphone, Headset, or Answer softkey.

Hold/Resume: Press Hold button. Press Resume or the flashing line key to retrieve.

Transfer Call: During active call, press Transfer, dial target number, press Transfer again.

Conference Call: During active call, press Conference, dial second party, press Conference again to join.

Voicemail: Press Messages button to access voicemail (configuration dependent).

Directory: Press Directory to view personal and corporate directories.

Call History: Press Applications and select Call History to view missed, received, and placed calls.

WARNING! Do not use the phone in a wet environment. Keep liquids away from the device.

Accessibility Features

Hearing Aid Compatibility (HAC): Handset is HAC rated. Visual Alerts: Flashing line key for incoming calls. Audio Adjustments: Independent volume control for handset, speakerphone, headset, and ringer.

Care & Cleaning

Disconnect power before cleaning. Use a soft, dry cloth to clean the exterior. For stubborn marks, dampen cloth slightly with water. Do not use abrasive cleaners, solvents, or sprays directly on the phone.

CAUTION! Never allow liquid to enter any openings on the phone. Avoid extreme temperatures.

Regulatory Information

FCC Part 15: This device complies with part 15 of the FCC Rules. Operation is subject to the condition that this device does not cause harmful interference. Copyright © Cisco Systems, Inc. All rights reserved. Cisco and the Cisco logo are trademarks of Cisco Systems, Inc. For technical support, contact your system administrator or visit www.cisco.com/go/sbw.

Troubleshooting

Symptom Possible Cause Corrective Action

Phone does not power on Power/PoE issue Check Ethernet cable connection to PoE switch; try external power adapter.

No dial tone Network/Registration Check network connectivity; verify phone is registered with call control system.

Poor audio quality Network/Handset Check for network packet loss; try different handset; adjust volume.

Display is blank/dim Settings/Power Adjust display contrast in Settings; ensure adequate power.

Cannot make external calls Dial plan/Service Verify dial plan configuration with administrator; check service status.

Reset: To restart phone, unplug Ethernet cable and reconnect, or use the Settings > Device Administration > Restart option.

Service: Contact your network administrator or Cisco Technical Support.

Cisco Phone 8851 Manual © - All Rights Reserved 2025

Symptom	Possible Cause	Corrective Action
Phone does not power on	Power/PoE issue	Check Ethernet cable connection to PoE switch; try external power adapter.
No dial tone	Network/Registration	Check network connectivity; verify phone is registered with call control system.
Poor audio quality	Network/Handset	Check for network packet loss; try different handset; adjust volume.
Display is blank/dim	Settings/Power	Adjust display contrast in Settings; ensure adequate power.
Cannot make external calls	Dial plan/Service	Verify dial plan configuration with administrator; check service status.