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no edit summary
<p>We now have functional DSP code and channel interface code to allow USB devices to interface with App_Rpt and Asterisk, allowing high-quality, yet inexpensive interconnection with radio devices.</p>
<p>We now have functional DSP code and channel interface code to allow USB devices to interface with App_Rpt and Asterisk, allowing high-quality, yet inexpensive interconnection with radio devices.</p>
==Zapata Telephony and how it relates to Asterisk PBX==
<p>By Jim Dixon, WB6NIL</p>
<p>About 20-25 or so years ago, AT&T started offering an API
(well, one to an extent, at least) allowing users
customize functionality of their Audix voicemail/attendant
system which ran on an AT&T 3BX usually 3B10) Unix platform.
This system cost thousands of dollars a port, and had very
limited functionality.</p>
<p>In an attempt to make things more possible and attractive
(especially to those who didnt have an AT&T PBX or Central
Office switch to hook Audix up to) a couple of manufacturers
came out with a card that you could put in your PC, which ran
under MS-DOS, and answered one single POTS line (loopstart
FXO only). These were rather low quality, compared with
today's standards (not to mention the horrendously pessimal
environment in which they had to run), and still cost upwards
of $1000 each. Most of these cards ended up being really bad
sounding and flaky personal answering machines.</p>
<p>In 1985 or so, a couple of companies came out with
pretty-much decent 4 port cards, that cost about $1000 each
(wow, brought the cost down to $250 per port!). They worked
MUCH more reliably then their single port predecessors, and
actually sounded pretty decent, and you could actually put 6
or 8 of them in a fast 286 machine, so a 32 port system was
easy to attain. As a result the age of practical Computer
Telephony had begun.</p>
<p>As a consultant, I have been working heavily in the area of
Computer Telephony ever since it existed. I very quickly
became extremely well- versed in the hardware, software and
system design aspects of it. This was not difficult, since I
already had years of experience in non-computer based telephony.</p>
<p>After seeing my customers (who deployed the systems that I
designed, in VERY big ways) spending literally millions of
dollars every year (just one of my customers alone would
spend over $1M/year alone, not to mention several others that
came close) on high density Computer Telecom hardware.</p>
<p>It really tore me apart to see these people spending $5000 or
$10000 for a board that cost some manufacturer a few hundred
dollars to make. And furthermore, the software and drivers
would never work 100% properly. I think one of the many
reasons that I got a lot of work in this area, was that I
knew all the ways in which the stuff was broken, and knew how
to work around it (or not).</p>
<p>In any case, the cards had to be at least somewhat expensive,
because they had to contain a reasonable amount of processing
power (and not just conventional processing, DSP
functionality was necessary), because the PC's to which they
were attached just didnt have much processing power at that time.</p>
<p>Very early on, I knew that someday in some "perfect" future
out there over the horizon, it would be commonplace for
computers to handle all of the necessary processing
functionality internally, making the necessary external
hardware to connect up to telecom interfaces VERY inexpensive
and in some cases trivial.</p>
<p>Accordingly, I always sort of kept a corner of an eye out for
what the "Put on your seatbelts, youve never seen one this
fast before" processor throughput was becoming over time, and
in about the 486-66DX2 era, it looked like things were pretty
much progressing at a sort of fixed exponential rate. I knew,
especially after the Pentium processors came out, that the
time for internalization of Computer Telephony was going to
be soon, so I kept a much more watchful eye out.</p>
<p>I figured that if I was looking for this out there, there
*must* be others thinking the same thing, and doing something
about it. I looked, and searched and waited, and along about
the time of the PentiumIII-1000 (100 MHz Bus) I finally said,
"gosh these processors CLEARLY have to be able to handle this".</p>
<p>But to my dismay, no one had done anything about this. What I hadn't
realized was that my vision was 100% right on, I just didnt know
that *I* was going to be one that implemented it.</p>
<p>In order to prove my initial concept I dug out an old Mitel
MB89000C "ISDN Express Development" card (an ISA card that
had more or less one-of-everything telecom on it for the
purpose of designing with their telecom hardware) which
contained a couple of T-1 interfaces and a cross-point matrix
(Timeslot- Interchanger). This would give me physical access
from the PC's ISA bus to the data on the T-1 timeslots
(albeit not efficiently, as it was in 8 bit I/O and the TSI
chip required MUCHO wait states for access).</p>
<p>I wrote a driver for the kludge card (I had to make a couple
of mods to it) for FreeBSD (which was my OS of choice at the
time), and determined that I could actually reliably get 6
channels of I/O from the card. But, more importantly, the 6
channels of user-space processing (buffer movement, DTMF
decoding, etc), barely took any CPU time at all, thoroughly
proving that the 600MHZ PIII I had at the time could probably
process 50-75 ports if the BUS I/O didnt take too much of it.</p>
<p>As a result of the success (the 'mie' driver as I called it)
I went out and got stuff to wire wrap a new ISA card design
that made efficient use of (as it turns out all of) the ISA
bus in 16 bit mode with no wait states. I was successful in
getting 2 entire T-1's (48 channels) of data transferred over
the bus, and the PC was able to handle it without any problems.</p>
<p>So I had ISA cards made, and offered them for sale (I sold
about 50 of them) and put the full design (including board
photo plot files) on the Net for public consumption.</p>
<p>Since this concept was so revolutionary, and was certain to
make a lot of waves in the industry, I decided on the Mexican
revolutionary motif, and named the technology and
organization after the famous Mexican revolutionary Emiliano
Zapata. I decided to call the card the "tormenta" which, in Spanish,
means "storm", but contextually is usually used to imply a
"*BIG* storm", like a hurricane or such.</p>
<p>That's how Zapata Telephony started.</p>
<p>I wrote a complete driver for the Tormenta ISA card for *BSD,
and put it out on the Net. The response I got, with little
exception was "well that's great for BSD, but what do you
have for Linux?"</p>
<p>Personally, Id never even seen Linux run before. But, I can
take a hint, so I went down to the local store (Fry's in
Woodland Hills) and bought a copy of RedHat Linux 6.0 off the
shelf (I think 7.0 had JUST been released but was not
available on shelf yet). I loaded it into a PC, (including
full development stuff including Kernel sources). I poked
around in the driver sources until I found a VERY simple
driver that had all the basics, entry points, interfaces, etc
(I used the Video Spigot driver for the most part), and used
it to show me how to format (well at least to be functional)
a minimal Linux driver. So, I ported the BSD driver over to
Linux (actually wasnt *that* difficult, since most of the
general concepts are roughly the same). It didnt have
support for loadable kernel modules (heck what was that? in
BSD 3.X you have to re-compile the Kernel to change
configurations. The last system I used with loadable drivers
was VAX/VMS.) but it did function (after you re-compiled a
kernel with it included). Since my whole entire experience
with Linux consisted of installation and writing a kernel
module, I *knew* that it *had* to be just wrong, wrong,
wrong, full of bad, obnoxious, things, faux pauses, and
things that would curl even a happy Penguin's nose hairs.</p>
<p>With this in mind, I announced/released it on the Net, with
the full knowledge that some Linux Kernel dude would come
along, laugh, then barf, then laugh again, then take pity on
me and offer to re-format it into "proper Linuxness".</p>
<p>Within 48 hours of its posting I got an email from some dude
in Alabama (Mark Spencer), who offered to do exactly that.
Not only that he said that he had something that would be
perfect for this whole thing (Asterisk).</p>
<p>At the time, Asterisk was a functional concept, but had no
real way of becoming a practical useful thing, since it
didnt, at that time, have a concept of being able to talk
directly (or very well indirectly for that matter, being that
there wasnt much, if any, in the way of practical VOIP
hardware available) to any Telecom hardware (phones, lines,
etc). Its marriage with the Zapata Telephony system concept
and hardware/driver/ library design and interface allowed it
to grow to be a real switch, that could talk to real
telephones, lines, etc.</p>
<p>Additionally Mark has nothing short of brilliant insight into
VOIP, networking, system internals, etc., and at the
beginning of all this had a great interest in Telephones and
Telephony. But he had limited experience in Telephone
systems, and how they work, particularly in the area of
telecom hardware interfaces. From the beginning I was and
always have been there, to help him in these areas, both
providing information, and implementing code in both the
drivers and the switch for various things related to this.
We, and now more recently others have made a good team (heck
I ask him stuff about kernels, VOIP, and other really
esoteric Linux stuff all the time), working for the common
goal of bringing the ultimate in Telecom technology to the
public at a realistic and affordable price.</p>
<p>Since the ISA card, I designed the "Tormenta 2 PCI Quad
T1/E1" card, which Mark marketed as the Digium T400P and
E400P, and now Varion is marketing as the V400P (both T1 and
E1). All of the design files (including photo plot files) are
available on the Zapatatelephony.org website for public consumption.</p>
<p>We have more, higher-density designs on the way.</p>
<p>As anyone can see, with Mark's dedicated work (and a lot of
Mine and other people's) on the Zaptel drivers and the Asterisk
software, the technologies have come a long, long way, and
continue to grow and improve every day.</p>
<p>Footnote:</p>
<p>Has anyone ever taken a moment to sit back and consider the
ENORMOUS responsibility that Mark has taken upon himself by
doing this project? Have you ever thought of how incredibly
many things that he has to concern himself with, and that it
just *NEVER ENDS*! At this point, I believe that I have
worked with him on this project longer that just about
anyone, including some of his employees, and believe me, I
have a good vantage point to see at least some of the stuff
that he has to go through to accomplish this.</p>
<p>Personally, I would have *NEVER* taken on such a task, being
that I am and was quite aware of the level of responsibility required
to do so.</p>
<p>Yes, the task that I took on was and is quite a task, and
quite a responsibility, but I did what I knew I could
accomplish. Mark's part is way larger then mine, and all I
can say that I know what it takes for him to do what he is
doing, and I seriously appreciate the time and dedication
that he has put into all the incredibly wonderful things that
he has done for it and all of us.</p>
<p>Furthermore, Id like to seriously thank all of the project
contributors and everyone else that has done some part to
help with this project. Thank you for demonstrating that you
believe in it, and that you believe in us.</p>