Yealink SIP-T54S Administrator's Manual page 1051

Appendix
When X=3, the default value is 5 (DND).
When X=4, the default value is 30 (Menu).
When X=5, the default value is 28 (History).
When X=6, the default value is 85 (Local Favorite).
When X=9, the default value is 33 (Status).
When X=13, the default value is 0 (NA).
For ext keys:
For SIP-T54S/T52S IP phones:
When Y=1-60, the default value is 0 (NA).
For SIP-T48G/T48S/T46G/T46S IP phones:
When Y=1-40, the default value is 0 (NA).
For SIP-T29G/T27P/T27G IP phones:
When Y=1, 21, the default value is 37 (Switch).
When Y=2-20, 22-40, the default value is 0 (NA).
Valid values are:
0-N/A
1-Conference
2-Forward
3-Transfer
4-Hold
5-DND
7-ReCall
8-SMS
9-Direct Pickup
10-Call Park
Range 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)
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