Cisco Telephone 8851 Instruction Manual

The Cisco IP Phone 8851 is a full-featured business VoIP telephone supporting high-definition voice, a color display, programmable line/feature keys, and Power over Ethernet (PoE). It integrates with Cisco Unified Communications Manager for enterprise-grade calling, messaging, and collaboration. Below are 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: Color LCD display, Handset, Speakerphone, Programmable line/feature keys, Navigation cluster, Volume rocker, Headset port, Ethernet ports.

Feature	Description
Display	5-inch color LCD with backlight
Audio	HD Voice, built-in speakerphone, headset support
Network	Dual Gigabit Ethernet ports (PC pass-through), PoE (802.3af)
Programmable Keys	Up to 4 line/feature keys for speed dial, call functions
Handset	Wideband capable for high-definition audio
Power	Power over Ethernet or optional external power adapter
Conference	Built-in support for multi-party conferencing
Security	Encrypted signaling and media (SRTP, TLS)
Headset Port	3.5mm jack for wired headset connection
Navigation Cluster	5-way navigation for menu access and call control

Installation

Unpack and inspect contents. Place on stable surface.

Connect to network: Plug Ethernet cable from switch into NETWORK port on phone.
Connect PC (optional): Use PC port to connect computer for network pass-through.
Connect handset: Plug coiled handset cord into HANDSET port.
Power the phone: Use PoE from switch or connect external power adapter.

WARNING! Use only approved power sources. Ensure network cables are securely connected.

First-Time Setup

Phone boots and registers with Cisco Unified Communications Manager.

Initial boot: Phone obtains IP address and downloads configuration.
Verify registration: Check for extension number on display.
Set preferences: Use Settings menu to configure language, time format, ringtones.
Program keys: Assign speed dial or feature keys via phone web interface or CUCM.

CAUTION! Do not unplug during firmware upgrade. Allow process to complete.

Specifications

Display: 5-inch color LCD, 480 x 272 pixels.
Audio Codecs: G.711, G.722, G.729, iLBC, Opus.
Network: 10/100/1000 Mbps Ethernet, 802.3af PoE.
Protocols: SIP, SCCP, HTTP/HTTPS, TFTP, DNS, DHCP, NTP.
Programmable Keys: 4 physical keys with dual LEDs.
Power Consumption: Max 6.3W (PoE).
Operating Temp: 32°F to 104°F (0°C to 40°C).
Compliance: FCC Part 15, CE, RoHS.

Controls and Settings

Access menus via NAVIGATION cluster. Front buttons: MESSAGES, DIRECTORY, HELP, SETTINGS, APPLICATIONS.

Basic Controls: Handset lift for call answer/end, SPEAKER button for speakerphone, MUTE button, VOLUME rocker, HEADSET button.

Settings: Language, Time Format (12/24 hr), Screen Contrast, Ringtone Selection, Network Configuration (via web interface). Phone Features: Call Forward, Do Not Disturb, Conference, Transfer, Hold, Park.

Connecting Devices

Network: NETWORK port to switch. PC: PC port to computer. Headset: 3.5mm jack.

Turn off devices before connecting cables.
Match cables to correct ports (Ethernet to NETWORK).
For headset, plug into 3.5mm jack and press HEADSET button to activate.

Tip: Use Cat5e or higher Ethernet cables for optimal performance.

Using Phone Features

Supports basic and advanced telephony features.

Make call: Lift handset or press SPEAKER, dial number, press Dial softkey.
Answer call: Lift handset, press SPEAKER, or press Answer softkey.
Hold: Press HOLD button during active call.
Transfer: Press TRANSFER, dial target number, press Transfer again.
Conference: Press CONFERENCE during call, dial second party, press Conference again.
Call Forward: Press CFwdALL softkey, enter destination number.
Voicemail: Press MESSAGES button to access.
Directory: Press DIRECTORY to view corporate or personal contacts.

WARNING! Do not expose phone to liquids. Keep vents clear for cooling.

Accessibility Features

Hearing Aid Compatibility (HAC): Handset meets FCC requirements. Visual Alerts: Flashing LED for incoming calls. Audio Adjustments: Separate volume controls for handset, speaker, ringer.

Care & Cleaning

Unplug power before cleaning. Use soft, dry cloth; mild detergent if needed. Avoid abrasive cleaners.

CAUTION! Do not spray liquids directly on phone. Keep away from extreme temperatures.

Regulatory Information

FCC Part 15: Class A digital device; complies with limits for business environments. CE Mark: Conforms to European EMC and safety directives. Copyright © 2025 Cisco Systems, Inc. For support, visit www.cisco.com/support or contact Cisco Technical Assistance Center.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No power	PoE/Power adapter	Check Ethernet cable; verify switch PoE enabled; try external power adapter.
No network registration	Network/DHCP	Check cable connections; verify DHCP server reachable; restart phone.
No audio	Volume/Mute	Adjust volume; check MUTE status; verify handset cord connected.
Display blank	Backlight/Power	Press any key to wake; check power source; adjust contrast in settings.
Calls not completing	Configuration	Verify dial plan; check CUCM configuration; contact administrator.

Reset: Press and hold # key during boot for factory reset (erases configuration).

Service: Contact network administrator or Cisco TAC: 1-800-553-2447.