[asterisk-users] Problem with ReceiveFax

Larry Moore lmoore at starwon.com.au
Tue Mar 13 08:19:16 CDT 2012

On 13/03/2012 8:10 PM, Ishfaq Malik wrote:
> On Tue, 2012-03-13 at 00:10 +0800, Larry Moore wrote:
>> On 12/03/2012 10:53 PM, Ishfaq Malik wrote:
>>> Thanks for the input so far. I'm going to keep plugging away and if
>>> anyone has any insights, they will be gladly appreciated. Ish
>> In SIP Account Configuration on Draytek;
>> Set Voice Active Detect to Off
>> In Phone Settings on the Draytek;
>> Enable Symmetric RTP
>> Check Start&  End RTP Ports match values set in /etc/asterisk/udptl.conf
>> for udptlstart&  udptlend
>> In /etc/asterisk/udptl.conf set;
>> use_even_ports=yes
> Thanks for the above, I was hoping to have replied earlier with a
> success message buy alas, no joy to be had.
> Could I be having some sort of DTMF issue? I noticed this in amongst the
> console output once I set the console logging level to include dtmf
> [2012-03-13 12:06:39] DTMF[24784]: channel.c:3976 __ast_read: DTMF end 'f' received on SIP/588-0000000c, duration 0 ms
> [2012-03-13 12:06:39] DTMF[24784]: channel.c:4002 __ast_read: DTMF begin emulation of 'f' with duration 100 queued on SIP/588-0000000c
> [2012-03-13 12:06:39] DTMF[24784]: channel.c:4138 __ast_read: DTMF end emulation of 'f' queued on SIP/588-0000000c
> does the above look correct for an inbound fax?
> Thanks in advance (again!)
> Ish

It's now time to do some debugging.

I would suggest you capture packets between asterisk and peer 588 using 
tcpdump, make sure you enable a large enough snaplen (-s) to ensure you 
capture all packets in the frame.

Submit your fax and upon completion of the session whether or not it is 
received successfully, transfer the file where you can open the captured 
file in Wireshark and select VoIP Calls located in the Telephony menu. 
You can then select the relevant line or lines in the session and click 
on the "Flow" button and review what is happening.

I have a Grandstream HT-503 at the other end of an IPSEC vpn which has 
the FXO port connected to a PSTN line.

I have configured the HT-503 to call the fax extension in the dialplan 
when it answers a call hence I have disabled faxdetect in the peer 

Looking at the Draytek manual I think this would be setup in VoIP >> 
Phone Settings by enabling Call Forwarding and setting it to "Always" 
and defining the SIP URL as fax@<astersk_server_ip>, assuming you have a 
fax extension enabled in the context of the peer. I am assuming you 
currently have this set to 200@<astersk_server_ip>.

Did you disable VAD on the Draytek.

I would also suggest you disable "Call Waiting" & "Call Transfer".

You may also want to look at "Volume Gain" in case that affects the 
level of the signal being converted to T.38 on the Draytek. Testing by 
progressively decreasing the level and if that doesn't help then 
increasing it.

Here is the peer configuration I just tested with my HT-503.

T.38 is enabled in the [general] section of sip.conf

g726nonstandard=yes             ;(this is required for Sipura and 
Grandstream ATAs, among others).

Good luck.


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