asterisk users - Mar 2009 - [Zaptel] Why no driver for PCI voice modems?

Hello

Considering how cheap PCI modems are compared to even the cheapest 
PCI hardware from Digium, OpenVox, Sangoma, etc.... I was wondering 
why Zaptel can't be used with those to connect an Asterisk server to 
a POTS line for low-level use? It just seems overkill for SOHO users 
who only get a few calls a day.

Is it because those modems are usually Windows-specific, and it would 
be too much work to have a working driver for Linux?

What about a Windows port of Asterisk and some glue to connect 
Asterisk to the modem driver?

Thank you.

Fred wrote:
> Hello
> 
> Considering how cheap PCI modems are compared to even the cheapest 
> PCI hardware from Digium, OpenVox, Sangoma, etc.... I was wondering 
> why Zaptel can't be used with those to connect an Asterisk server to 
> a POTS line for low-level use? It just seems overkill for SOHO users 
> who only get a few calls a day.
Hi Fred, just purchase an X100[p] clone on ebay. I bought one last year 
from a seller in the USA and it cost me about ?17 (GBP) including shipping.

Using Zaptel and OSLEC it is absolutely fine.

HTH

Alan

PS - I did a quick search and here is the type of thing I mean. I have 
no idea of the seller or this particular board but you get the idea I'm 
sure: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220380070996

On Tue, Mar 31, 2009 at 03:09:39PM +0200, Fred wrote:
> Hello
> 
> Considering how cheap PCI modems are compared to even the cheapest 
> PCI hardware from Digium, OpenVox, Sangoma, etc.... I was wondering 
> why Zaptel can't be used with those to connect an Asterisk server to 
> a POTS line for low-level use? It just seems overkill for SOHO users 
> who only get a few calls a day.
It would take someone to write drivers for at least one type of common
modems.
> 
> Is it because those modems are usually Windows-specific, and it would 
> be too much work to have a working driver for Linux?
The software in those propriatary drivers is intended for using those
cards directly as modems or faxes. DAHDI has slightly different uses for
them.

-- 
               Tzafrir Cohen
icq#16849755              jabber:tzafrir.cohen at xorcom.com
+972-50-7952406           mailto:tzafrir.cohen at xorcom.com
http://www.xorcom.com  iax:guest at local.xorcom.com/tzafrir

On Tuesday 31 March 2009 08:09:39 Fred wrote:
> Considering how cheap PCI modems are compared to even the cheapest
> PCI hardware from Digium, OpenVox, Sangoma, etc.... I was wondering
> why Zaptel can't be used with those to connect an Asterisk server to
> a POTS line for low-level use? It just seems overkill for SOHO users
> who only get a few calls a day.
If half-duplex audio is good enough for you, sure.  That is, if you can deal
with audio flowing in only only direction, it would work.  This is usually a
hardware limitation that cannot be overcome by changing the driver.  Only
a fraction of the hardware available is actually capable of full duplex audio.
> Is it because those modems are usually Windows-specific, and it would
> be too much work to have a working driver for Linux?
It's not a matter of too much work.  It's a problem of having the right
information from the manufacturer and a problem of finding a person
skilled enough to write the driver.
> What about a Windows port of Asterisk and some glue to connect
> Asterisk to the modem driver?
This has been done before, in theory.  Asterisk certainly compiled on
Windows, although from what I understand, it did not work particularly
well.  You would also need people to maintain the port, as bitrot is what
happened to all of the previous efforts, after the porter went on to other
projects.

What it really comes down to is a value proposition:  if you are not willing
to spend the money to purchase a hardware card for a little over $100 for
a single port card, then are you willing to invest your time into writing
and testing either a driver or a port of Asterisk to Windows?  Remember that
either proposition is likely to need weeks (or months) of your time.  Is your
time better spent on that task, or is your time better spent working on other
jobs that would earn you the money to purchase a card from a company that is
willing to maintain the drivers and the software, to ensure that both continue
to work?

-- 
Tilghman

----- "Wilton Helm" <whelm at compuserve.com> wrote:
> 
>If half-duplex audio is good enough for you, sure. 
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.
>Only a fraction of the hardware available is actually capable of full duplex
audio.
> 
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.
>What it really comes down to is a value proposition: 
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?

Wilton 

If the primary purpose is to drive down cost, why not simply buy any one of the
existing 'Wildcard X100P' clone cards that are everywehere? They're
inexpensive and readily available...

--Tim 
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Fred wrote:
> Hello
> 
> Considering how cheap PCI modems are compared to even the cheapest 
> PCI hardware from Digium, OpenVox, Sangoma, etc.... I was wondering 
> why Zaptel can't be used with those to connect an Asterisk server to 
> a POTS line for low-level use? It just seems overkill for SOHO users 
> who only get a few calls a day.
Hi Fred, just purchase an X100[p] clone on ebay. I bought one last year
from a seller in the USA and it cost me about ?17 (GBP) including shipping.

Using Zaptel and OSLEC it is absolutely fine.

HTH

Alan

PS - I did a quick search and here is the type of thing I mean. I have
no idea of the seller or this particular board but you get the idea I'm
sure: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220380070996

Tzafrir Cohen wrote:
> On Thu, Apr 02, 2009 at 08:28:44PM +0800, Steve Underwood wrote:
>
>   
>> Several Winmodem chips are still readily available, and so are cards 
>> containing them. What is missing is someone putting the effort into 
>> making drivers for them.
>>     
>
> Can you list, off the top of your head, modems for which the relevant
> information is probably available?
>
>   
Go to the Linmodems mailing list, and look at the things people are 
getting to work with their Linux machines today. Most of those chips can 
be programmed for 8k sampling, although as modems they usually sample at 
9.6k second (It can simply the maths a bit, even though it means working 
with more samples). From a quick scan I did a year or two ago, the 
source code for most of the drivers gives you the starting point you need.

Steve