Yealink SIP-T29G User Manual page 207

Auto LineKeys is
If
for a registered shared line on the phone.
Click Confirm to accept the change.
3.
To configure the shared line settings and the number of line key on phone A via web user
interface:
Register the primary account 4603.
1.
you can automatically assign multiple DSS keys with Line type
enabled,
Advanced Phone Features
195