[incoming]

exten => s,1,Answer
exten => s,n,Background(hawaii)
exten => s,n,WaitExten
exten => s,n,Hangup

exten => fax,1,SetVar(FAXFILE=/var/spool/asterisk/fax/${UNIQUEID}.tif)
exten => fax,n,rxfax(${FAXFILE})
exten => fax,n,Hangup