Yealink SIP-T2 SERIES Administrator's Manual page 590

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
Parameters
X ranges from 1 to 2 (for SIP-T21(P) E2)
For ext keys:
X ranges from 1 to 6, Y ranges from 1 to 20, 22 to 40 (Ext key 21 cannot be configured).
Example:
linekey.2.type = 20
Default:
For SIP VP-T49G/SIP-T48G IP phones:
The default value of the line key 1-16 is 15, and the default value of the line key 17-29 is 0.
For SIP-T46G/T29G IP phones:
The default value of the line key 1-16 is 15, and the default value of the line key 17-27 is 0.
For SIP-T42G IP phones:
The default value of the line key 1-12 is 15, and the default value of the line key 13-15 is 0.
For SIP-T41P IP phones:
The default value of the line key 1-6 is 15, and the default value of the line key 7-15 is 0.
For SIP-T27P IP phones:
The default value of the line key 1-6 is 15, and the default value of the line key 7-21 is 0.
For SIP-T40P/T23P/T23G/T21(P) E2 IP phones:
The default value is 15.
For ext keys:
When Y=1, the default value is 37 (Switch).
When Y= 2 to 20, 22 to 40, the default value is 0 (NA).
Note: It is not applicable to SIP-T19(P) E2, CP860 IP phones.
Web User Interface:
DSSKey->Line Key->Type
Phone User Interface:
Menu->Features->DSS Keys->Line Key X->Type
linekey.X.label/
expansion_module.X.key.Y.label
Description:
(Optional.) Configures the label displayed on the LCD screen for each DSS key.
For line keys:
X ranges from 1 to 29 (for SIP VP-T49G/SIP-T48G)
X ranges from 1 to 27 (for SIP-T46G/T29G)
X ranges from 1 to 15 (for SIP-T42G/T41P)
566
Permitted
Values
String within
99 characters
Default
Blank