[Asterisk-Users] Fax over 2 bridged TE110P channels

[Alessio Focardi]

On 4/4/06, Remco Barende <asterisk at barendse.to> wrote:
>
> I suspect that in your case the fax channels are not natively bridged. I'm
> not sure whether native bridging will work if you are using 2 cards.



Tnx to all who replied to me, I'm posting a reply I received from Digium
support for reference to other having the same problem:

Officially, fax communications is not supported, because the precision
of the timing and jitter is not sufficient for clean enough transmission
of the fax signalling to offer 100% reliable performance.

That being said, faxing generally works over bridged TDM connections.
The problem you are likely having is one or both of the following:

1. The timing sync of the cards is not going to work as desired: You are
taking timing from the telco (assumably) on one card, and in order for
the fax bridge to work properly, you'd have to re-send that timing
signal out the other card. The timing coming out of the other card (the
pri_net span) is not synced to the other span -- it is being generated
by the internal clock on the card itself. Due to this, the timing sync
is not making it from the telco to the other PBX. It is possible to sync
spans across cards only with the 2 and 4-span cards using a timing cable
between them. It is also possible to sync timing if you had a single
dual-span card servicing both the E1s instead.

2. Less likely: the bridge across the spans is traversing the PCI bus,
and system resource contention might be tainting the signal, introducing
jitter, or possibly dropping frames.





You might want to check with Digium support to verify
>
> Let me know the result.
>
> Cheers!
> Remco
>
>
> On Tue, 4 Apr 2006, Alessio Focardi wrote:
>
> > Hi,
> >
> > I have an asterisk installation with 2 E1 cards
> >
> > Software version is
> >
> > Asterisk 1.2.6
> > Libpri 1.2.2
> > Zaptel 1.2.5
> >
> > I'm having problem with fax transmission, let me explain better my
> > setup:
> >
> >
> > My fist TE110P E1 card is connected to the telco line
> > the second TE110P E1 one to an Nexspan PBX
> >
> > so the server is basically sitting between the line, and the pbx.
> >
> > every call coming from the line is simply redialed in the pbx
> > every call from pbx is simply redialed to the line
> > no answer is done
> >
> > All is working great with voice, but faxing often results in error, both
> > receiving and sending.
>
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