Yealink SIP-T2 SERIES Administrator's Manual page 371

Parameter
Description:
Configures a return code and reason of SIP response messages when the IP phone
rejects an incoming call. A specific reason is displayed on the caller's phone LCD
screen.
404-Not Found
480-Temporarily Unavailable
486-Busy Here
603-Decline
If it is set to 486 (Busy Here), the caller's phone LCD screen will display the message
―Busy Here‖ when the callee rejects the incoming call.
Web User Interface:
Features->General Information->Return Code When Refuse
Phone User Interface:
None
To specify the return code and the reason when refusing a call via web user interface:
1. Click on Features->General Information.
2. Select the desired value from the pull-down list of Return Code When Refuse.
3. Click Confirm to accept the change.
Early media refers to media (e.g., audio and video) played to the caller before a SIP
Configuring Basic Features
Permitted Values Default
349