[default]
exten => fax,1,Goto(fax-in,fax,1)

[fax-in]
exten => fax,1,Answer
exten => fax,2,Set(FAXFILE=/var/spool/astersik/fax/i${CALLERIDNUM}-${TIMESTAMP}.tif)
exten => fax,3,rxfax(${FAXFILE})
exten => h,1,hangup


and no faxdetect on zapata.com