Yealink SIP-T2 SERIES Administrator's Manual page 428

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
Parameters
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)
For ext keys:
X ranges from 1 to 6, Y ranges from 1 to 20, 22 to 40 (Ext key 21 cannot be configured).
Permitted Values:
1 to 16, 150 (for SIP VP-T49G)
1 to 16 (SIP-T48G/T46G/T29G)
1 to 12 (for SIP-T42G)
1 to 6 (for SIP-T41P/T27P)
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
150-H.323 account
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 directed call pickup feature code followed by the monitored extension.
404
Permitted Values
String within 99
characters
Default
Blank