Answeronpolarityswitch and no ring back tone


I have pabx in a flash box and installed with TDM800P fxo card. with that I can make calls to PSTN numbers via digium card and i can hear ring back tone successfully. Any way When i mentioned answeronpolarityswitch=yes in chan_dahdi.conf file under {channel] it make small problem. Which is when i do it i can’t hear the ring back tone which is coming from pstn network to sip side. as soon as call get connect and asterisk receive the line reversal signal it set up the call path and i can hear the b party voice. As i observed, asterisk will not make the audio part until it get the answer signal from PSTN side.

I tried to search about this issue on the net. But couldn’t find a successful answer. It’s really critical me about accurate CDR logs.

Please advice.


I found another clue. When the asterisk play different kind of recordings like “all circuits are busy now” also i cant hear from sip phone. At that moment i didn’t on answeronpolarityswitch. That mean normally also asterisk activate the voice path only call get success. So i think its not issue with answeronpolarityswitch option. It happen because asterisk will set the audio path only call get answer.

How can i fix this issue ???