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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I don’t think a off the shelf modem has the necessary DSPs
to convert voice to codec….that is why a Voice Gateway/Analog Telephony
Adapter or FXO/FXS cards exist instead of modem having a second life.<o:p></o:p></span></p>
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color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I do recall a few that worked as a answering machine allowing
your home computer to answer calls ,etc.<o:p></o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] <b>On Behalf Of </b>Wilton
Helm<br>
<b>Sent:</b> Wednesday, April 01, 2009 1:06 PM<br>
<b>To:</b> Asterisk-users@lists.digium.com<br>
<b>Subject:</b> Re: [asterisk-users] [Zaptel] Why no driver for PCI voice
modems?<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>>If half-duplex audio is good enough for you, sure.<o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>You've
lost me there. I am not aware of a modem that is for sale today that is
half duplex. (OK some support a couple of minor half duplex modes). All
state of the art modem protocols send and receive simultaneously using the full
300 - 3000 Hz bandwidth in both directions with adaptive equalization and echo
cancellation to make it work, which is pretty much what a voice circuit
need. There are two differences: 1) The response and quality of a
current modem must be considerably higher than what is needed for voice use or
it would never achieve the throughput expected of it, and 2) the adaptive
equalization algorithm is designed around modem specific techniques. The
latter is (especially for a softmodem) a software issue, not a hardware
limitation.</span><o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal>>Only a fraction of the hardware available is actually
capable of full duplex audio.<o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Absolutely
not the case. Particularly the softmodems (the most inexpensive) contain
little else than what is required for placing and answering full duplex audio
calls. Everything else is in the driver. The OP is 100% correct,
that they would be an excellent candidate for FXO use in low volume
applications.</span><o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal>>What it really comes down to is a value
proposition: <o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Quite
true. This is the real issue. As mentioned, these drivers require
considerable skill and knowledge to write. While there is no doubt that
the result would be very cost effective, the business model is lacking.
The modem manufacturer is going to see the potential market for this as
somewhere down in the noise compared to their normal modem sales, so isn't
inclined to invest. A third party developer with the skills would have a
difficult time recouping development costs (let alone any profit) because they
don't control the hardware, and therefore have no leverage. A user with
enough volume to justify paying for the development (or doing it if they had
the skill) probably has enough volume to use T1s instead. If
everyone that could benefit from using a modem card were to pitch in $10
towards the development, it would probably be quite possible. But how to
make that happen?</span><o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Wilton</span><o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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