Hello! I'm try to implement a fax service using spandsp (0.0.2-pre10) and NVFaxDetect (since I'm using a SIP channel). I receive the call from pstn on my SIP/PSTN gateway (welltech 3804). The fax is detected by NVFaxDetect and than a macro is started. The welltech use Alaw codec. The problem is the following: NOTICE[22270]: Dropping incompatible voice frame on SIP/192.168.103.139-0817a2e0 of format slin since our native format has changed to alaw It seems the "slinear" codec is set inside the fax applications but I don't really understand why, since it should be possible to use G711 codecs for faxes within lightly loaded LAN. Here is my extension.conf exten => s,1,Wait(6) exten => s,2,Answer exten => s,3,DigitTimeout(10) exten => s,4,ResponseTimeout(20) exten => s,5,NVFaxDetect(10) exten => s,6,Background(vm-extension) exten => fax,1,Goto(fax,2201,1) [macro-faxreceive] exten => s,1,SetVar(FAXFILE=/var/spool/asterisk/fax/${UNIQUEID}.tif) exten => s,2,DBGet(EMAILADDR=extensionemail/${MACRO_EXTEN}) exten => s,3,rxfax(${FAXFILE}) exten => s,103,SetVar(EMAILADDR=me@mysys.com) exten => s,104,Goto(3) [fax] exten => 2201,1,Macro(faxreceive) exten => 2202,1,Macro(faxreceive) exten => 2203,1,Macro(faxreceive) exten => h,1,system(/usr/local/sbin/mailfax ${FAXFILE} ${EMAILADDR} "${CALLERIDNUM} ${CALLERIDNAME}") Here is my relevant sip.conf [pstn01] context = pstn-gw type = friend host = 192.168.103.139 dtmfmode = inband qualify = yes port = 5060 canreinvite = no disallow = all allow = alaw Any help is appreciated. Thnks