Yealink SIP-T48S User Manual page 167

(Optional.) Enter the busy forward on code or off code respectively in the On
3)
Code or Off Code field.
You can also enable busy forward for all accounts. Do the following:
Tap the All Lines soft key.
1)
The touch screen prompts "Copy to all lines?".
Tap OK to accept the change or Cancel to cancel.
2)
If you select No Answer Forward:
c)
Tap the On radio box of the No Answer Forward field.
1)
Enter the destination number you want to forward unanswered incoming calls to
2)
in the Forward to field.
Tap the gray box of the After Ring Time field, and then select the desired ring
3)
time to wait before forwarding from the pull-down list.
The default ring time is 12 seconds.
Basic Call Features
157