[Asterisk-Dev] PRI receive and answer supervision

Matthew Simpson matthew at txlink.net
Sun Jun 12 09:21:02 MST 2005

Hello everyone,

I'm trying to use the Newman Fax Detect script to detect outgoing faxes 
dialed from a PRI into a Digium TE-405P.  If I detect a fax, it shunts the 
fax out a Zap channel instead of trying to handle it VoIP.  The fax detect 
works if I don't pass it the "n" flag -- which in the faxdetect code will 
signal asterisk to answer the line.  Unfortunately, that screws up CDRs on 
busy/noanswer calls.  Passing the "n" flag does not answer the line.

I've been digging through chan_zap.c and channels.c but I can't find any 
particular section of code that would handle audio frames received by the 
PRI before answer supervision is set.  Can anyone point me in the right 

Is it even possible to listen in on a PRI call before Answer supervision is 
sent for the fax machine "beep" ?  The switch I have asterisk hooked up to 
via pri is our Lucent switch so maybe the Lucent won't send anything until 
it gets answer-sup ?


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