[asterisk-users] Fax from FXS to PRI

[Steve Totaro]

On Tue, Sep 20, 2011 at 4:43 PM, Adam Moffett <adamlists at plexicomm.net>wrote:

> If I have a 4 port Digium FXS card and a single port PRI card on the same
> asterisk box, is it expected that I'd be able to plug a fax machine into the
> analog FXS port and have no problems sending or receiving faxes?  Our
> connection to the Telco is on the PRI obviously.
>
> I don't recall the specific card models that we have, but I can check if it
> matters.
>
> Does the version of asterisk or Zaptel matter?
>
> My related question is this: In the scenario described above does the audio
> pass directly from one card to the other through the PCI bus or does it have
> to somehow be processed by software?
>
>
Nobody can say for sure.  It is not a supported configuration.  I can tell
you that I have had great success and wasted days messing around with this
configuration.

It is usually the other side's fax machine, a cheap all in-one, or it is TX
and RX gains, or IRQs, or......

Questions to ask are
1.  Is this for your system or are you installing for someone else?  You
could look very bad if the proper expectations are not set.  It may take a
great deal of trial and error to get to an acceptable level, if you can even
do that based on need.

2.  Needs, if fax is part of the lifeblood, then this route may not be the
best.  If it doesn't hurt to ask someone to resend or whatever, then go for
it.

Just remember the gotchas, IRQs, TX RX gain settings, echo can when bridged
=no.

Again, it has never been a supported configuration by Digium, and everyone
that has dealt with faxing in Asterisk especially on different systems will
tell you that you won't know until you try.  And even then, is it worth days
of your time trying to get it as close to a POTS line as possible?

Another issue I have run into are the Digium FXS daughter boards getting
fried somehow.  I punch on a 66 block now and put on surge protection after
frying six modules in as many years.  Something like this
http://www.digitaltele.com/ProductInfo.aspx?productid=HCO

I have never had to do that on the FXS side but now it is just standard for
all single pairs I do.  I will know in the next year or two if it helps.  No
idea what is frying the daughterboards.  Must be the fax machine.

Thanks,
Steve T

Thanks,
Steve T
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