Yealink SIP-T54S Administrator's Manual page 455

Details of the Configuration Parameter:
Parameter
features.normal_refuse_code
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:
Click on Features->General Information.
1.
Select the desired value from the pull-down list of Return Code When Refuse.
2.
Click Confirm to accept the change.
3.
Configuring Basic Features
Permitted Values
404, 480, 486 or 603
Default
486
429