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

[Tim Nelson]

----- "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 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.digium.com/pipermail/asterisk-users/attachments/20090401/32a64502/attachment.htm