Documented specifications
Cisco · Cisco support listed the 9800 Series as available at review. Remaining support period, local stock, price and exact calling-platform entitlement were not established.
| Specification | Documented value |
|---|---|
| Display | 3.7-inch backlit color LCD, 480 × 240 Source ↗ |
| Line controls | Six physical line keys and up to 46 line or programmable-line assignments. Maximum SIP lines are platform-specific: 130 on CUCM or Webex Dedicated Instance and 16 on Webex Calling or Open SIP platforms. Source ↗ |
| Ethernet | Internal two-port 10/100/1000BASE-T switch Source ↗ |
| Wireless | No integrated Wi-Fi or Bluetooth documented for the 9851 Source ↗ |
| USB | One USB-A and one USB-C. Under PoE, each is documented at 0.5 A/5 V; USB-A rises to 1 A/5 V with Cisco Power Adapter 3 while USB-C remains 0.5 A/5 V. Source ↗ |
| PoE | Class 3 Source ↗ |
| Expansion | One 9800 KEM through USB-A under PoE class 3 or Cisco Power Adapter 3; the KEM is powered by the host phone Source ↗ |
Unlisted fields remain unverified. Platform compatibility and remaining support life require confirmation for the exact ordered model.
Separate six keys from assignments and SIP lines
The 9851 has a 3.7-inch 480 × 240 color display and six physical line keys. Cisco separately lists up to 46 line or programmable-line assignments and platform-dependent maximum SIP lines: 130 for CUCM or Webex Dedicated Instance and 16 for Webex Calling or Open SIP platforms. None of these figures is simultaneous-call capacity. Record the selected platform, the pages users must navigate and the monitored-line workflow before replacing an existing key layout.
Keep it a wired desk-phone decision
Cisco documents the two-port Gigabit Ethernet switch for the 9851 but limits integrated Wi-Fi and Bluetooth statements to the 9861 and 9871 radio models. Do not transfer those radios to the 9851 or use a reseller's family-level description as proof. The 9841 is a simpler grayscale four-key comparison, while the 9861 is the relevant step up when integrated wireless, a larger display or more physical line keys are required.
Budget the two USB ports and one KEM
The 9851 provides USB-A and USB-C. Under PoE, Cisco documents 0.5 A at 5 V for each; with Cisco Power Adapter 3, USB-A rises to 1 A at 5 V while USB-C remains 0.5 A at 5 V. The host supports one 9800 KEM under either PoE class 3 or the local adapter, and the KEM has no independent supply. Its USB output also changes with the host power arrangement. Test the exact KEM, headset, charging load, cable path, overload warning and restart sequence rather than assuming both ports and the module can each draw their headline maximum together.
Pilot platform features and protection separately
Cisco lists SIP and SDP, TLS signaling, SRTP media, 802.1X, EAP-TLS, secure boot, credential storage, HTTPS, E911 location mechanisms and a Problem Report Tool for the family. These are capabilities, not proof that the selected tenant, PBX, switch, certificate chain or emergency-location service has configured them. Platform-marked calling, directory, hot-desking, headset, meeting and management features must be accepted on the exact PhoneOS release and calling service.
For an authorized pilot, test activation, inbound and outbound calling, two-way audio, all intended line-key pages, hold, blind and attended transfer, directory search, voicemail indication, headset control, power recovery and the approved non-live emergency procedure. Preserve a requested diagnostic bundle before reboot and protect it as sensitive operational evidence. No phone, firmware, platform, account, key layout, USB load, KEM, protected session, emergency workflow, availability, price or call was tested for this review.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.
Examples require adaptation to your topology. No live PBX or hardware testing is claimed.