Faxing over DAHDI

tom@intersoft.net.au

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#1
Hi,

I'm trying to set up faxing (with hylafax) and am having trouble getting it to send or receive over DAHDI trunks (openvox a400p fxo).

Incoming:
Fax detection is working (both 'zaptel' and NVfax), the call is sent to the IAX fax extension, and you can hear the start of the 'handshake' on the fax machine side. Then, as soon as the first few fax tones finish the call is dropped and the physical fax machine says "Comm Error".

Outgoing:
The fax machine rings, picks up the call, and again you can hear the handshake start. Then the call is dropped and the fax machine says "Comm Error". The message in the Hylafax log is
Code:
ERR No carrier detected
The strange thing is I can send out over a SIP trunk (by changing the outbound route only) and it works. So clearly its got something to do with the DAHDI side of things.

I have installed AvantFAX using the script on these forums and it made no difference.

I am currently running 1.5RC4.

Here is my chan_dahdi.conf
Code:
[trunkgroups]

[channels]
context=from-pstn
signalling=fxs_ks
rxwink=300              ; Atlas seems to use long (250ms) winks
usecallerid=yes
hidecallerid=no
callwaiting=yes
usecallingpres=yes
callwaitingcallerid=yes
threewaycalling=yes
transfer=yes
canpark=yes
cancallforward=yes
callreturn=yes
echocancel=yes
echocancelwhenbridged=no
faxdetect=incoming
echotraining=800
rxgain=2.0
txgain=1.0
callgroup=1
pickupgroup=1

;Uncomment these lines if you have problems with the disconection of your analog lines
busydetect=yes
busycount=3


immediate=no

#include dahdi-channels.conf
#include chan_dahdi_additional.conf
Thanks in advance for any info.
 

DaveD

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#2
You may need to increase your TX and RX gains some more, it will vary with certain fax machines you are faxing to and receiving from.

Try setting at around rXgain=6 and TXgain =3 and see if it improves.
I used to have similar issues on zaptel until I upped the gains.Now I just use SIP for all faxes in and out with no issues
 

ramoncio

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#3
Have you run fxotune?
This should improve sound quality, and faxing too.
 

tom@intersoft.net.au

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#4
Thanks DaveD, after raising the gains to the values you suggested I can receive via the FXOs but I still can't send.

Ramoncio, thanks for the tip, no I haven't ran fxotune. Do I just run
Code:
fxotune -i
or do I need to give it some more arguments?
 

tom@intersoft.net.au

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#5
EDIT: Ignore me, I've now read the instructions... I'll report back with the difference it makes.

Ok, so I did:
Code:
amportal stop
fxotune -vvvvvvvvvv -i -b 1 -e 4
fxotune -s
amportal start
And I still can't send over dahdi trunks... Still getting the same 'No Carrier' message.
 

DaveD

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#6
Ok that suggests the TX gain is not high enough, for a test just up the TX gain to 6 as well.

I send all my faxes via SIP using ulaw or alaw with no issues
 

tom@intersoft.net.au

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#7
I tried increasing the TX gain to 6.0 and still have the same problem. Also, do I need to add fxotune -s anywhere to get it to use the tuning config file or does it do it automatically after a restart?

EDIT:
It seems we have a dodgy line. Increasing the rx to 6 and tx to 3 got incoming faxes working, but not outgoing, I just put 2 and 2 together to consider that we were receiving on one line and sending on another. I've tried switching the lines to different FXOs but the problem always follows the line.

Thanks for your help.
 

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