Yealink SIP-T54S Administrator's Manual page 896

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series/CP860/CP920 IP Phones
When Y=12, the default value is opus;
For SIP-T48G/T46G/T42G/T41P/T29G/CP860:
When Y=1, the default value is PCMU;
When Y=2, the default value is PCMA;
When Y=3, the default value is G723_53;
When Y=4, the default value is G723_63;
When Y=5, the default value is G729;
When Y=6, the default value is G722;
When Y=7, the default value is iLBC;
When Y=8, the default value is G726-16;
When Y=9, the default value is G726-24;
When Y=10, the default value is G726-32;
When Y=11, the default value is G726-40;
For SIP-T27G:
When Y=1, the default value is PCMU;
When Y=2, the default value is PCMA;
When Y=3, the default value is G729;
When Y=4, the default value is G722;
When Y=5, the default value is iLBC;
When Y=6, the default value is G726-16;
When Y=7, the default value is G726-24;
When Y=8, the default value is G726-32;
When Y=9, the default value is G726-40;
When Y=10, the default value is opus;
When Y=11, the default value is G723-53;
When Y=12, the default value is G723-63;
For SIP-T40P/T40G/T23P/T23G/T21(P) E2/T19(P) E2:
When Y=1, the default value is PCMU;
When Y=2, the default value is PCMA;
When Y=3, the default value is G729;
When Y=4, the default value is G722;
When Y=5, the default value is iLBC;
When Y=6, the default value is G726-16;
When Y=7, the default value is G726-24;
When Y=8, the default value is G726-32;
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Parameters
Permitted
Default
Values