Yealink SIP-T48G User Manual page 199

Select Enabled from the pull-down list of Audio Alert for BLF Pickup.
3.
Click Confirm to accept the change.
4.
Note
Visual and audio alert features are configurable via web user interface only.
To configure BLF ring type via phone user interface:
Tap ->Basic->Sound->BLF Ring Type.
1.
Tap or
2.
Tap the desired ring tone.
3.
(Optional.) Press
4.
Tap the Save soft key to accept the change or
5.
BLF ring type is configurable via web user interface at the path Features->Call Pickup.
When the monitored line receives an incoming call, the following occurs on your phone:
The phone plays a specific ring tone (if enabled).

to scroll through the list of available ring tones.
to adjust the ringer volume.
Advanced Phone Features
to cancel.
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