Yealink SIP-T48S User Manual page 161

If you enable DND for all accounts, all line icons will change to
on the status bar.
When DND and busy forward are enabled for a specific account, calls from the specific account
Note
will be sent to the configured destination number. For more information on busy forward, refer
to Call Forward
To configure the DND authorized numbers via web user interface:
Click on Features->Forward&DND.
1.
Select Enabled from the pull-down list of DND Emergency.
2.
Enter the numbers in the DND Authorized Numbers field.
3.
For multiple numbers, enter a comma between every two numbers.
Click Confirm to accept the change.
4.
When DND is enabled on the phone, the phone can still receive incoming calls from the
on page152.
Basic Call Features
and the icon will appear
151