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Date:      Wed, 25 Mar 1998 11:01:24 +0100
From:      Ulltveit-Moe  Nils <etonumo@eto.ericsson.se>
To:        Peter Simons <simons@rhein.de>
Cc:        freebsd-isdn@FreeBSD.ORG
Subject:   Fax
Message-ID:  <9803251001.AA18606@dinosaur>
In-Reply-To: <x7vht316b1.fsf@petium.rhein.de>
References:  <x7vht316b1.fsf@petium.rhein.de>

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Peter Simons writes:
 > -----BEGIN PGP SIGNED MESSAGE-----
 > 
 > Hi,
 > 
 > does anyone know a software that can receive/send fax over ISDN? I am
 > using a Fritz!Card, which can handle group 3 (analogous) fax, but I
 > can't find any hint in the i4b software that this is supported in any
 > way.
 
This is probably not implemented.

Implementing G3 fax in ISDN would mean simulating an analog modem
on the digital link. This means having to generate the right waveforms
for the modulated data, and receive analog data from the other end
which you had to run FFT analysis on and then interpret.

In addition you have to do this in realtime, to be able to deal with
the timing involved in the fax protocol, something neither
FreeBSD or Linux is good at in their native form.. 

A third point is that a software simulated faxmodem usually does not
work well. I tested Teles software faxmodem in Win-95 towards an Ericsson V34
HE modem, and was able to send faxes from the ISDN card at 4800 baud
only, and receive faxes ad 9600 baud only(!) (And it is not the
Ericsson modems fault, it works flawlessly towards other fax machines.)

My point is that the best thing to do is to use an ordinary faxmodem
to handle faxes with Hylafax of mgetty+sendfax or efax, or you may use
a combined ISDN card with an analog part.

Of course, if you are crazy enough, you may try to implement a
software simulated modem in e.g. RT-linux, or a similar realtime
extension for FreeBSD.

Best regards,
Nils Ulltveit-Moe







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