Yealink SIP-T27P User Manual page 191

To register an account and configure BLA feature on phone A via web user interface:
Register the account 14019833020.
1.
Click on Advanced, and then select Draft BLA from the pull-down list of Shared Line.
2.
Enter the desired number in the BLA Number field.
3.
Click Confirm to accept the change.
4.
Advanced Phone Features
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