[asterisk-users] Faxing through Zap cards

[C F]

On Wed, Sep 3, 2008 at 3:11 PM, Karl Fife
<asterisk-users at kfife.mailworks.org> wrote:
> On Tue, 2 Sep 2008 11:38:17 -0500, "James Sneeringer"
> <jsneerin at gmail.com> said:
>> On Sun, Aug 31, 2008 at 1:45 AM, C F <shmaltz at gmail.com> wrote:
>> > No, in the beginning you asked because you don't have the experience
>> > so folks like myself that do have the experience answered. It might
>> > work for you, no one knows and you THINK it will work, it's a hit and
>> > miss, stability is huge issue, thats where experience comes in. If you
>> > want something that I or the other people here just think works, then
>> > just get an ATA. If you want something we have experienced and know
>> > that it works, then get a channel bank.
>
> I'd like to draw on your experience.  At one point you mentioned that
> the
> fax stability goes from perfect to "anybody's guess" when the call
> leaves the PRI card.  I think I understand the underlying architecture
> well enough to know why this is the case.  Here's the question:
>
> In an installation where there are only Analog Telco drops, can
> pri/channel bank reliability be achieved on analog cards by keeping fax
> traffic *within* a single Digium TDM card *because* of the fact that
> card would not be subject to the limitations of the PCI/PCX interface
> bus and/or underlying OS?  For example 4 analog fax lines into (and out
> of) a single TDM800--4 telco lines to 4 FXO, 4 fax machines from 4 FXS).
>
> Do you have any practical or theoretical knowledge as to whether similar
> reliability to the PRI/Channel-bank setup can be achieved PROVIDED that
> traffic is never allowed to leave the internals of the card.  Depending
> on how ZAP services the card, there may be exactly ZERO difference
> between the aforementioned setup and one involving multiple SEPARATE
> cards.  If traffic stays within the card, where (if anywhere) does the
> process becomes compromised?

I do this with a TDM2400 card and it works fine, but I only have it in
one location like that, as I don't like it. I don't like the TDM2400
card (or any other analog 2 wire zap cards), and have since started
using only channel banks, and I don't like using fax machines thru
asterisk if the setup is only POTS. If a customer is running only POTS
then they have a line dedicated as a fax line, in which case there is
usually no point in having the fax line connected to the PBX. However,
if the customer has a PRI then they are in most cases using a DID
coming in over the PRI for faxing, in which case terminating that fax
connection out of Asterisk on an FXS port is important. I have tried
with Zap FXS cards (in a separate PCI slot than the PRI card) and
faxing was not stable enough. The only time I was able to predict the
stability of faxing was when using a multi port T1 Zap card where one
is connected to a channel bank.


>
> Certainly it would be trivial to design a card that could handle fax
> pass-through, so the logical conclusion seems to be that NOT having done
> so was done to achieve a GREATER good in a mutually exclusive design
> trade-off.  I'm sure that I (and others) would be very interested to
> gain a better understanding of this if you (or anyone) can speak
> intelligently to it.

That greater good might have been that faxing is a technology of the past :)


>
> Thanks
>
> -Karl
>
>
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