Polycom VVX C Business Media Phone for Cisco Unified Communications Manager (SIP) - Manual (Page 44)

Deployment Guide for the Polycom VVX 1500 C
A - 6
To add a shared line—a line shared with other phones—edit the reg
parameter. For example:
Messaging <msg/>
Message-waiting indication is supported on a per-registration basis.
Edit the msg parameter to set the single-button voice mail feature. For example:
User Preferences <up/>
By default, the screen saver feature is disabled and the digital picture frame
feature looks for images stored in the root folder on the USB flash drive.
Edit the up parameter to enable the screen saver feature and set another
location for images. For example:
Note msg.mwi.1.callBackMode must be set to contact for proper operation with Cisco
Unified Communications Manager. msg.mwi.1.callBack must be set to the voice
mail pilot number.