You may use any standards-based audio endpoint that connects to Cisco Unified Communications Manager to join a WebEx meeting on the conferencing system. The supported audio endpoints include the Cisco IP Phones, Telepresence endpoints, and PSTN devices such as mobile phones and landline phones. Many audio endpoints support audio and video connectivity. However, only audio connectivity to the Cisco WebEx Meetings Server is supported.
To permit users from outside the organization to join WebEx meetings using PSTN devices, your company must deploy Analog-to-VoIP Gateways such as Cisco Integrated Service Routers (ISR).
For a list of Cisco Unified IP Phones supported by Cisco Unified Communications Manager and the Device Packs available for each model, see http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/compat/devpack_comp_mtx.html#wp262585.