[Asterisk-Users] Which is the best fax-modem for testing ?

[HaoXu]

Hi Rich Adamson,

I am very happy to get such rich fax on Asterisk info. 
But I still have a question. If I have some external pstn gateway, they
could send fax very well in peer to peer mode, Can it work with asterisk?
How to do it? 

Thanks.

Hawk

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Rich Adamson
Sent: Tuesday, May 16, 2006 3:43 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [Asterisk-Users] Which is the best fax-modem for testing ?

> Which fax-modem would you pick if you had to test fax capabilities ?
>  
> For instance, before releasing a new PBX system offering fax 
> connectivity, you would like to make sure you "comply" with most fax 
> machines and protocols.
> As you can't afford you buy and maintain tens of such fax machines nor 
> can't afford to test by hand each protocol, it's tempting to buy an 
> all-inclusive fax-modem and run a program instead.
> Which one would you choose for that ?

The fax modem is not really the issue with asterisk. By far, the majority of
existing analog fax machines installed and being sold today will function
just fine with asterisk.

If you sell an asterisk system into an analog pstn environment, any fax
machine will function through asterisk "if" you use the Sangoma A200D analog
card with fxo and fxs modules. (Very stable and very reliable fax
transmissions.)

If you sell an asterisk system into a digital pstn environment (eg, PRI),
any fax machine will work with Sangoma or Digium digital cards, however the
fxs interface to the fax machine "may be" very questionable in terms of
reliability and usability.

If you sell an asterisk system with external pstn gateways (eg, ATA
adapters), better be careful as the majority of inexpensive gateways will
not function reliably with an analog fax machine.

If you're thinking T.38 fax capability, forget it for now. Some folks were
working on adding T.38 support into asterisk, but its not in stable code as
yet to the best of my knowledge.  Also, according to Steve Underwood, T.38
implementations in current fax machines are of questionable quality.

If you're thinking in terms of high volume faxing, then look towards the
hylafax (or whatever) approach.

If you're thinking in terms of faxing via VoIP providers, reliability will
be less then acceptable "if" you get it to work at all.

Bottom line: the most reliable method of integrating fax support into an
asterisk system "today" (without implementing hylafax or whatever) is
through the use of the Sangoma A200D analog card, as it keeps the pcm data
flow "on the card" (fxs -> fxo); and, removes the impact that pci bus,
shared interrupts, system applications, ethernet dropped packets or jitter,
ATA issues, and other disruptive elements from the analog fax data path.

If you search the list archives for the past two years, you'll find a couple
of "point" solutions other then mentioned above that do work, but most of
them are "dependent" on some specific element (eg, full moon) that cannot be
reliably replicated in every asterisk installation.


_______________________________________________
--Bandwidth and Colocation provided by Easynews.com --

Asterisk-Users mailing list
To UNSUBSCRIBE or update options visit:
   http://lists.digium.com/mailman/listinfo/asterisk-users