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Added all html-files on i4lfax web-pages for easy updating by all developers.

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Morten Rolland 1999-08-28 18:46:56 +00:00
parent 7216b4f4be
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
<meta name="KeyWords" content="V.21, V.29, V.17, fax, modem, DSP, modulation, demodulation">
<title>i4lfax - Software fax solution</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
<td valign=top>
<table width=200 cellpadding=3>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top><h2><a href="index.html">Back to<br>main page</a></h2></td></tr>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top>Last updated Jun. 5 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
</table>
</td>
<td valign=top>
<table width=560>
<td>
<h1>Availability</h1>
<p>We do not wish to distribute the code widely yet.
The main reason for this is that we simply do not want people
to believe that there is even a pre-alpha version available,
simply to save us the trouble of answering requests and
questions related to the code. But please feel free and
do us a favor by asking questions that you can't find the
answer to on these pages!</p>
<p>There is simply no code available that needs testing on
a large scale yet, so please accept our decision on this issue
until we have something we want to share with you.</p>
</td>
</table>
</td>
</tr>
</table>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
<meta name="KeyWords" content="V.21, V.29, V.17, fax, modem, DSP, modulation, demodulation">
<title>i4lfax - Software fax solution</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
<td valign=top>
<table width=200 cellpadding=3>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top><h2><a href="index.html">Back to<br>main page</a></h2></td></tr>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top>Last updated Jun. 2 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
</table>
</td>
<td valign=top>
<table width=560>
<td>
<h1>The banner graphics</h1>
<p>The banner above was designed using 'gimp' on a Linux workstation.
During the hours spent on designing the graphics, I learned a lot
about 'gimp', which basically was my motivation for spending so much
time designing it. It is probably very naive, but it was fun making it.</p>
<p>Appart from the obvious fax-page on the left, there is a 'signal-space
diagram' that shows the complex signal-points plotted in a Re/Im coordinate
system. Basically, a point (marked with a cross) designates a given
four-bit binary sequence. The distance of a point from the center indicates
what amplitude the modulation carrier must have to transmit the given four-bit
binary sequence, while the angle indicates how much the carrier has to be
phase-shifted. With 16 signal-points, there is one point for each possible
four-bit sequence, which makes it possible to transfer 4 bits in one
"symbol-period" or "baud". In V.29 there are 2400 symbol periods per second,
which gives a bit-rate of 4&nbsp;x&nbsp;2400 => 9600&nbsp;bit/s.</p>
<p>The curve is what a given set of signal-points may translate
into in terms of digital samples, which gradually gets smoothed as they
turn analog somewhere along the line before they finaly reach the destination
fax-machine.</p>
<p>The background is basically random sequences of 0/1, but a repeating
pattern of '01111110' can be seen, which is the "flag-sequence" used
in the synchronous HDLC link-level protocol used among other places, in fax
transfers.</p>
</td>
</table>
</td>
</tr>
</table>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
<meta name="KeyWords" content="V.21, V.29, V.17, fax, modem, DSP, modulation, demodulation">
<title>i4lfax - Software fax solution</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
<td valign=top>
<table width=200 cellpadding=3>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top><h2><a href="index.html">Back to<br>main page</a></h2></td></tr>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top>Last updated Jun. 2 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
</table>
</td>
<td valign=top>
<table width=560>
<td>
<h1>Want to help?</h1>
<p>The existing development team is quite busy on other projects and
real-life tasks, so we don't think we can be of much support to
new developers at this point. If you do have experience in digital signal
processing or otherwise believe that you can contribute to the project
let us know and we will see what we can do (The current effort
is still low-level DSP algorithms mostly).</p>
<p>One of the problems is that the framework for how it all should
get tied together is not fully in place yet, so we fear at this
point in development that more programmers only will bring
management effort up and productivity down.</p>
<p>This is a very non-Bazar like approach to Open Source development,
and we are not very happy about it, so we would welcome suggestions.</p>
<p>Once the fundamental signal processing algorithms are in place,
we expect to open up as more unrelated challenges will spring into
existence.</p>
<p>Also see <a href="availability.html">Availability.</a></p>
</td>
</table>
</td>
</tr>
</table>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
<meta name="KeyWords" content="V.21, V.29, V.17, fax, modem, DSP, modulation, demodulation">
<title>i4lfax - Software fax solution</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
<td valign=top>
<table width=200 cellpadding=3>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top><h2><a href="index.html">Back to<br>main page</a></h2></td></tr>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top>Last updated Jun. 2 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
</table>
</td>
<td valign=top>
<table width=560>
<td>
<h1>How does it work?</h1>
<p>Audio can be digitally sampled like on a music-CD or sound-card.
A computer can run software algorithms on such digital samples
that mimic the inner workings of a standard modem that may itself be designed
purely from amplifiers, filters, signal-generators and what-not.</p>
<p>Actually, a software algorithm can also do stuff that is
practically impossible with standard electronic circuits, so all modern
modems uses one or several software algorithms to perform signal analysis
and generation. New 56k modems would be impossible where it not for
such software algorithms. A special breed of processors called
<i>"Digital Signal Processors"</i> (DSPs) are mostly used for this kind of
task, as they are designed to cope with the enormous amounts of
multiplications, additions and fast/strange indexing that are
usually needed by the software algorithms.</p>
<P>In modems that uses software algorithms, the circuits needed to connect
to the phone-line resembles that of a sound-card; they can turn the
incomming signal into digital samples, and they can convert the outgoing
digital samples into an electrical signal suitable for the phone-line.
Most of what happens inside a modern modem is thus the result of a
computer program. There is basically no reason why this computer program
can't be run on the main processor of the computer instead of inside the
modem, except from:</p>
<ol>
<li>The algorithms has to be developed/known, or licensed from a company
with experience from modem design</LI>
<li>Running the software algorithms of a modem may be too demanding for
the main processor of the computer.</li>
</ol>
<p>The second point is no longer very relevant, as computers keep
getting faster all the time, with the occational big leap like
the SIMD extensions of the Pentium. The first point however, is the reason
why there is no such software for Linux. We hope to change this.</p>
<p>By using the (soft-) realtime scheduler in the standard Linux kernel
and disabeling paging for the modem software, the problems with running
a timing-critical task on a multiuser system can be solved.</p>
<p>By using an ISDN-system, the audio-samples can be sent directly
towards a remote fax-machine without any other equipment than the ISDN-card.
There will probably be support for Win-modems some time in the future if
specifications can be obtained.</p>
</td>
</table>
</td>
</tr>
</table>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
<meta name="KeyWords" content="V.21, V.29, V.17, fax, modem, DSP, modulation, demodulation">
<title>i4lfax - Software fax solution</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
<td valign=top>
<table width=200 cellpadding=3>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top><h2><a href="motivation.html">Motivation<a/></h2></td></tr>
<tr><td valign=top><h2><a href="license.html">License</a></h2></td></tr>
<tr><td valign=top><h2><a href="platforms.html">Platform</a></h2></td></tr>
<tr><td valign=top><h2><a href="yes.html">Will it work?</a></h2></td></tr>
<tr><td valign=top><h2><a href="how.html">How does it work?</a></h2></td></tr>
<tr><td valign=top><h2><a href="team.html">Project members</a></h2></td></tr>
<tr><td valign=top><h2><a href="help.html">Want to help?</a></h2></td></tr>
<tr><td valign=top><h2><a href="availability.html">Availability</a></h2></td></tr>
<tr><td valign=top><h2><a href="resources.html">Resources</a></h2></td></tr>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top>Last updated Aug. 23 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
</table>
</td>
<td valign=top>
<table width=560>
<td>
<h1>Introduction to i4lfax</h1>
<p>The 'i4lfax' (or 'isdnfax') project aims to provide the neccesary open source software
to use a computer as a fax-machine without the need for a dedicated fax-modem. This project
thus aims to provide a <i>Software only</i> fax solution.</p>
<p>Some basic method of communication with remote fax-machines must be available.
The 'ISDN4Linux' subsystem can provide this connection over ISDN-lines on a Linux
system. A 'Win-modem' may provide the voice-connection needed on a standard
phone-line.</p>
<p>The project development started out on the Linux platform, and no attempt to
port has yet been made. There should be few problems porting to other modern
platforms, but at this early stage of development this is not a priority task.</p>
<p>The digital signal processing algorithms needed to implement a fax solution
is expected not to burden a Pentium grade CPU unacceptably.</p>
<hr>
<h1>Quick project status</h1>
<p>Some of the successes so far:
<ul>
<li>Simulated 9600 bit/s V.29 modulation/demodulation on a perfect line</li>
<li>Successfully decoded initial control-messages from a fax-machine</li>
<li>300 bit/s communication with real modem/fax over ISDN using V.21 standard</li>
<li>Made use of the real-time scheduler in a standard Linux kernel</li>
<li>Established a framework for chaining DSP-modules</li>
<li>ISDN4Linux has proved to work well as a voice-carrier.</li>
</ul>
As can be seen, development effort is directed towards the low-level modulation,
demodulation and link-level algorithms needed to get the basic communications
up and running. The problem areas that needs investigation before this project gets off
the ground are many and large, so please don't hold your breath waiting for a working release.</p>
<p>Part of the problem is all the things about digital signal processing we have
to learn along the way...</p>
</td>
</table>
</td>
</tr>
</table>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
<meta name="KeyWords" content="V.21, V.29, V.17, fax, modem, DSP, modulation, demodulation">
<title>i4lfax - Software fax solution</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
<td valign=top>
<table width=200 cellpadding=3>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top><h2><a href="index.html">Back to<br>main page</a></h2></td></tr>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top>Last updated Jun. 2 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
</table>
</td>
<td valign=top>
<table width=560>
<td>
<h1>License</h1>
<p>The license is a variant of the open X/MIT license, basically not limiting the
use and distribution of the software at all, as long as the original copyrights are
preserved.</p>
<p>All source-files carry one or more copyrights and the license like
the following:</p>
<hr>
<font size=-1>
<pre>
Fax program for ISDN.
Copyright (C) 1999 Morten Rolland [Morten.Rolland@asker.mail.telia.com]
Copyright (C) 1999 ...
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
</pre>
</font>
</td>
</table>
</td>
</tr>
</table>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
<meta name="KeyWords" content="V.21, V.29, V.17, fax, modem, DSP, modulation, demodulation">
<title>i4lfax - Software fax solution</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
<td valign=top>
<table width=200 cellpadding=3>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top><h2><a href="index.html">Back to<br>main page</a></h2></td></tr>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top>Last updated Jun. 2 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
</table>
</td>
<td valign=top>
<table width=560>
<td>
<h1>Motivation</h1>
<p>The different project team members initially had somewhat different motivation,
and probably still have. But the following points probably covers most of them:
<ul>
<li>Educational. There is very little DSP-software freely available for use on
standard computers. A working fax-machine designed purly as free software could be
a great aid to future signal processing professionals (Project team members
included!).</li>
<li>Practical. With ISDN installed at home, at least in Norway, you need
to buy a separate adapter or an expensive phone with analog phone-line sockets
in order to be able to use a standard fax-machine or fax-modem. A much simpler
and less expensive setup would be possible if Linux could send and receive faxes
over the ISDN-line directly.</li>
<li>Challenge 1. Users of MS Windows can send and receive faxes using
inexpensive ISDN-cards, and it is about time Linux catches up in this
arena!</li>
<li>Challenge 2. The fact that a fax-modem needs some timing-critical
code to work is a challenge to the Linux operating-system as such. In the
Windows world, the fax-modems seems to be implemented as relatively low-level
drivers with lots of backing resources. It is a challenge to implement the
same functinality in a user-program on Linux, as the kernel is quite large
enough already, thank you! (Except for flexible logical volume management
and virtualized and safe graphics card drivers which I'd
like to see in the kernel...)</li>
</ul>
</td>
</table>
</td>
</tr>
</table>
</body>
</html>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
<meta name="KeyWords" content="V.21, V.29, V.17, fax, modem, DSP, modulation, demodulation">
<title>i4lfax - Software fax solution</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
<td valign=top>
<table width=200 cellpadding=3>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top><h2><a href="index.html">Back to<br>main page</a></h2></td></tr>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top>Last updated Jun. 5 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
</table>
</td>
<td valign=top>
<table width=560>
<td>
<h1>Platform</h1>
<p>The current development platform is Linux with the ISDN4Linux subsystem
operational with full-duplex audio-mode capability. I (Morten) personally run a rather
old version of the HiSax driver on a Linux 2.0.35 system with a Teles 16.3 card.</p>
<p>All cards/drivers may not support full-duplex audio over ISDN.
If you run the 'vbox' answering-machine, you have voice-support, question is
if it's full duplex.</p>
<p>As long as the core algorithms are under development, there will probably be no
efforts made to support other platforms, as there is little point in spending
(possibly wasting) effort until we either have more developers with other
local setups or working software.</p>
</td>
</table>
</td>
</tr>
</table>
</body>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990823: New resources page with links">
<meta name="KeyWords" content="isdn, fax, modem, DSP, modulation, demodulation">
<title>Linux/i4lfax/ISDN resources</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
<td valign=top>
<table width=200 cellpadding=3>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top><h2><a href="index.html">Back to<br>main page</a></h2></td></tr>
<tr><td valign=top>&nbsp;</td></tr>
<tr><td valign=top>Last updated Aug. 23 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
</table>
</td>
<td valign=top>
<table width=560>
<td>
<h1>Linux/i4lfax/ISDN resources</h1>
<p><a href="http://www.linmodems.org/">http://www.linmodems.org/</a><br>
This is an effort to get vendor support for 'Win-modems' which are basically
a soundcard that connects to the phone-line. In MS-Windows, the host CPU
takes care of the DSP calculations needed to run fax, modem etc. just like
the i4lfax project. The i4lfax project will try to support Win-modems
as well as ISDN if possible.</p>
<p><a href="http://www.pctel.com/">http://www.pctel.com/</a><br>
PC-TEL is a company selling Win-Modem solutions, and claims to have
working software for Linux.</p>
<p><a href="http://www.mhessler.de/i4lfaq.html">http://www.mhessler.de/i4lfaq.html</a><br>
The FAQ for the 'Isdn4Linux' project. This project makes it possible to
use some types of ISDN-cards with Linux.</p>
<p><a href="ftp://ftp.aeccom.com/pub/fax4i4l/howto/current/">ftp://ftp.aeccom.com/pub/fax4i4l/howto/current/</a><br>
This site deals with faxing under Linux with an "AVM B1" (active ISDN-card ).</p>
</td>
</table>
</td>
</tr>
</table>
</body>
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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
<meta name="KeyWords" content="V.21, V.29, V.17, fax, modem, DSP, modulation, demodulation">
<title>i4lfax - Software fax solution</title>
</head>
<body text="#FFFFFF" bgcolor="#000000" link="#00EE00" vlink="#00EE00" alink="#00EE00">
<table border=0 cellspacing=0 cellpadding=0>
<tr>
<td colspan=3><a href="banner.html"><img src="i4lfaxbanner.gif" height=110 width=760 border=0></a></td>
<tr>
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<tr><td valign=top>Last updated Jun. 6 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
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<h1>Project Members</h1>
<p>Current team members on the 'i4lfax' project:</p>
<p>Andreas Beck, <a href="mailto:Andreas Beck <andreas.beck@ggi-project.org>">andreas.beck@ggi-project.org</a><br>
<a href="http://www-public.rz.uni-duesseldorf.de/~becka/">http://www-public.rz.uni-duesseldorf.de/~becka/</a></p>
<p>Morten Rolland, <a href="mailto:Morten Rolland <Morten.Rolland@asker.mail.telia.com>">Morten.Rolland@asker.mail.telia.com</a><br>
<a href="http://home.telia.no/Morten.Rolland/">http://home.telia.no/Morten.Rolland/</a></p>
<p>Thomas Reinemann, <a href="mailto:Thomas Reinemann <tom.reinemann@gmx.net>">tom.reinemann@gmx.net</a><br></p>
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<meta name="HISTORY" content="19990602: First web-announce of i4lfax Software Fax OSS project">
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<tr><td valign=top>Last updated Jun. 2 1999 by <a href="mailto:Morten.Rolland@asker.mail.telia.com">Morten&nbsp;Rolland</a></td></tr>
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<h1>Will it work?</h1>
<p>The short answer: Yes!</p>
<p>The long answer: There seems to be no technical limitations preventing
us from implementing the DSP software needed on a Linux system to do it all
in software.</p>
<p>Needless to say, there is a <i>lot</i> of rather complicated software
needed and we only have limited resources and knowledge, but we think it is
possible to solve this problem through an "Open Source Software" project.</p>
<p>One argument against a software-only modem/fax that has circulated and
apparently gained some acceptance points out that the timing-critical nature
of a modem makes it very difficult, maybe even impossible to make it work.
Needless to say, nothing is impossible, as the existence of such software for
Win 95/98/NT demonstrates.</p>
<p>The fax-standards makes some allowances for latency, which is a godsend
as it reduces the need to respond </i>immediately</i> to an incomming
signal. A software-only solution with some latency can be viewed as a
fax-machine that seems to be a little more remote than it really is.
A satelite jump is aprox. 0.25 seconds, which is a long time compared to
the extra latency expected to be introduced by buffering in software.</p>
<p>With a slow or busy computer, the fax-algorithms could be expected to
respond too slowly or too sluggish to keep the connection running.
The project team has looked into this problem, and we can proudly announce
that the soft-realtime scheduler in any standard Linux kernel seems more
than able to solve this problem.</p>
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