Yealink SIP-T54S Administrator's Manual page 1047

Appendix
61-Directory
66-Paging List
73-Custom Key (only appear when the parameter
"features.enhanced_dss_keys.enable" is set to 1)
85-Favorite (Local Favorite) (only applicable to
CP860/CP920 IP phones)
For ext keys:
Valid types are:
0-NA
1-Conference
2-Forward
3-Transfer
4-Hold
5-DND
7-ReCall
8-SMS
9-Direct Pickup
10-Call Park
11-DTMF
12-Voice Mail
13-Speed Dial
14-Intercom
15-Line
16-BLF
17-URL
18-Group Listening
20-Private Hold
22-XML Group
23-Group Pickup
24-Multicast Paging (Paging)
25-Record
27-XML Browser
34-Hot Desking
35-URL Record
37-Switch (only applicable to ext key 1 for SIP-
T29G/T27P/T27G IP phones)
38-LDAP (only appear when the parameter
1021