Yealink SIP-T2 SERIES Administrator's Manual page 442

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
1 to 3 (for SIP-T40P/T23P/T23G)
1 to 2 (for SIP-T21(P) E2)
1-Line 1
2-Line 2
...
16-Line 16
Note: It is not applicable to SIP-T19(P) E2 and CP860 IP phones.
Example:
linekey.1.line = 1
Web User Interface:
DSSKey->Line Key/ Programable Key->Line
Phone User Interface:
Menu->Features->DSS Keys->Line Key X->Account ID
linekey.X.value/ programablekey.X.value/
expansion_module.X.key.Y.value
Description:
Configures the group call pickup feature code.
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)
X ranges from 1 to 21 (for SIP-T27P)
X ranges from 1 to 3 (for SIP-T40P/T23P/T23G)
X ranges from 1 to 2 (for SIP-T21(P) E2)
For programable keys:
X=1-4, 12-14 (for SIP VP-T49G)
X=1-10, 12-14 (for SIP-T48G/T46G)
X=1-10, 13 (for SIP-T42G/T41P/T40P)
X=1-14 (for SIP-T29G/T27P)
X=1-10, 14 (for SIP-T23P/T23G/T21(P) E2)
X=1-9, 13, 14 (for SIP-T19(P) E2)
X=1-6, 9, 13 (for CP860)
For ext keys:
X ranges from 1 to 6, Y ranges from 1 to 20, 22 to 40 (Ext key 21 cannot be
420
Parameters Permitted Values
String within 99
characters
Default
Blank