Yealink SIP-T2 SERIES Administrator's Manual page 612

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
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=1-6, 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 configured).
Example:
linekey.1.value = 224.5.5.6:10008
Note: The valid multicast IP addresses range from 224.0.0.0 to 239.255.255.255. It is not
applicable to SIP-T19(P) E2 IP phones.
Web User Interface:
DSSKey->Line Key->Value
Phone User Interface:
Menu->Features->DSS Keys->Line Key X->Value
linekey.X.label/
programablekey.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)
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 ranges from 1 to 4.
For ext keys:
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 IP phones.
Web User Interface:
DSSKey->Line Key->Label
Phone User Interface:
588
Parameters Permitted Values
String within 99
characters
Default
Blank