asterisk users - Jun 2007 - Strange beeping sound during fax initiate session

Hello!

We have a strange problem, which doesnt let us receive faxes, because  
during the initial fax whistling there are suddenly some background  
beeps showing up, which then naturally disable any successfull fax  
transfer, and we cant figure out which service or device (cisco,  
asterisk) is responsible for these beep-sounds.

Calls go from EuroISDN PSTN (E1) into a Cisco 5300, which is  
configured for voice service mode, g711alaw and has a dial peer  
called asterisk, to which it sends SIP calls preceeding some number  
match.

Asterisk 1.2.16 receives a msg and usually responds with a ConnectTo 
(xyznumber) msg telling the Cisco 5300 what do to. The xyz-Number is  
most of the time our IVR system with NMS cards for voice-recording,  
voice-menus, call managment and fax send & receive, but some calls go  
back to PSTN and terminate in a fax machine.

Voice works fine. DTMF detection and handling in our IVR solutions  
works like a charm.

If I reroute PSTN calls past Cisco+Asterisk directly into another E1  
trunk on the NMS cards we can receive fax fine without a problem. So  
on the IVR solution I m very confident that there is no problem.

However faxes fail to pass through the Cisco+Asterisks territory.  
Unfortunately I m not at the liberty to connect "some other  
equipment" at the Cisco and check it, this particular 5300 is always  
calling our asterisk and gets a ConnectTo() back how to handle the  
incoming call.

Although these details are very limited, have you ever seen a similar  
problem in a comparable environment? You call by PSTN into a Cisco  
5300 who asks Asterisk what to do, then gets you connect to a fax  
machine and then you hear the initial tones and then after a few  
seconds there are beeps (which disrupt naturally the fax protocol)?  
Found a solution for it?

Regards
Philipp Ott

Hello!
> Although these details are very limited, have you ever seen a  
> similar problem in a comparable environment? You call by PSTN into  
> a Cisco 5300 who asks Asterisk what to do, then gets you connect to  
> a fax machine and then you hear the initial tones and then after a  
> few seconds there are beeps (which disrupt naturally the fax  
> protocol)? Found a solution for it?
Yes - asterisk 1.2.16 injects the beep tone, for whatever reason,  
when it "hears" the typical fax modem whistling on the passing alaw  
stream.

Downgrading to 1.2.14 or upgrading to 1.2.18 resolves the problem.

This is a standard asterisk install with make & make install.

Regards