Yealink SIP-T54S Administrator's Manual page 586

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series/CP860/CP920 IP Phones
Procedure
Send user=phone can be configured using the following methods.
Central Provisioning
(Configuration File)
Web User Interface
Details of the Configuration Parameter:
account.X.enable_user_equal_phone
Description:
Enables or disables the IP phone to add "user=phone" to the SIP header of the INVITE
message for account X.
0-Disabled
1-Enabled
X ranges from 1 to 16 (for SIP-T54S/T48G/T48S/T46G/T46S/T29G)
X ranges from 1 to 12 (for SIP-T52S/T42G/T42S)
X ranges from 1 to 6 (for SIP-T41P/T41S/T27P/T27G)
X ranges from 1 to 3 (for SIP-T40P/T40G/T23P/T23G)
X ranges from 1 to 2 (for SIP-T21(P) E2)
X is equal to 1 (for SIP-T19(P) E2/CP860/CP920)
Web User Interface:
Account->Advanced->Send user=phone
Phone User Interface:
None
To configure send user=phone feature via web user interface:
Click on Account->Advanced.
1.
Select the desired account from the pull-down list of Account.
2.
560
<MAC>.cfg
Parameter
Configure send user=phone feature
on a per-line basis.
Parameter:
account.X.enable_user_equal_phone
Configure send user=phone feature
on a per-line basis.
Navigate to:
http://<phoneIPAddress>/servlet?p
=account-adv&q=load&acc=0
Permitted Values
0 or 1
Default
0