Yealink SIP-T54S Administrator's Manual page 677

Parameters
X ranges from 1 to 3 (for SIP-T40P/T40G/T23P/T23G)
X ranges from 1 to 2 (for SIP-T21(P) E2)
For ext keys:
For SIP-T54S/T52S:
X ranges from 1 to 3, Y ranges from 1 to 60.
For SIP-T48G/T48S/T46G/T46S:
X ranges from 1 to 6, Y ranges from 1 to 40.
For SIP-T29G/T27P/T27G:
X ranges from 1 to 6, Y ranges from 1 to 20, 22 to 40 (Ext key 21 cannot be configured).
Note: It is not applicable to SIP-T19(P) E2/CP860/CP920 IP phones.
Web User Interface:
Dsskey->Line Key->Label
Phone User Interface:
Menu->Features->DSS Keys->Line Key X->Label
linekey.X.shortlabel
(X ranges from 1 to 21)
Description:
(Optional.) Configures the short label displayed on the LCD screen for line key.
Note: It is only applicable to SIP-T52S IP phones.
Web User Interface:
Dsskey->Line Key->Short
Phone User Interface:
Menu->Features->DSS Keys->Line Key X->Short Label
To configure an ACD key via web user interface:
Click on Dsskey->Line Key.
1.
In the desired DSS key field, select ACD from the pull-down list of Type.
2.
(Optional.) Enter the string that will appear on the LCD screen in the Label field.
3.
Configuring Advanced Features
Permitted
Values
String within
99 characters
Default
Blank
651