AMD – ANSWER MACHINE DETECTION
https://www.voip-info.org/asterisk-cmd-amd/
AMD([|initialSilence][|greeting][|afterGreetingSilence][|totalAnalysisTime][|minimumWordLength][|betweenWordsSilence][|maximumNumberOfWords][|silenceThreshold])
<< Example block
— AMD: initialSilence [2500] greeting [1500] afterGreetingSilence [800] totalAnalysisTime [5000] minimumWordLength [100] betweenWordsSilence [50] maximumNumberOfWords [3] silenceThreshold [256] maximumWordLength [5000]
<< Example block
from the log file, we know, 2500 is the default value of initialSilence, 2.5 second
to tweak these parameters, for example:
exten => _X.,n,AMD(2000|1350|1600|5000|100|50|3|200)
exten => _X.,n,verbose(AMD EXIT CAUSE ${AMDCAUSE} ${AMDSTATUS} )