Thanks for the feedback. <div><br></div><div>I have plenty of experience with IVRs and Dialogic cards (starting with D121/LSI120s and SS96s under DOS in the 90's all the way up to Intel's DM/Vs) and didn't ever have a problem with DTMF collection with ISDN PRI lines except occasionally with wireless and cell phones (Bad line quality).</div>
<div><br></div><div>These new cards are so much cheaper than the Dialogic cards were, I should just buy the version with the cancellers.</div><div><br></div><div>Tony</div><div><div><div><br></div><div><br><div class="gmail_quote">
On Tue, Mar 17, 2009 at 11:36 AM, Steve Underwood <span dir="ltr"><<a href="mailto:steveu@coppice.org">steveu@coppice.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im">David Knell wrote:<br>
> Steve Underwood wrote:<br>
>>> When there is Echo being generated from the far end, usually in a<br>
>>> bridged call. If you application is just an IVR, with no far end<br>
>>> connectivity, then you shouldn't need an echo can. If you are bridging<br>
>>> calls, then at some point you may need it, depending on what else is<br>
>>> in the loop.<br>
>>><br>
>> This is VERY VERY WRONG. IVRs badly need echo cancellation. Without it<br>
>> they give very poor reliability detecting DTMF while the prompts are<br>
>> playing. If the system uses voice recognition, its reliability will be<br>
>> even worse.<br>
>><br>
> With respect, this is at best half true. DTMF detection has always<br>
> worked just fine<br>
> without echo cancellation - the Dialogic, Aculab and Rhetorex cards<br>
> which I used<br>
> in the late 1990s managed it perfectly well; if the DTMF detection<br>
> code in * and FS<br>
> can't, then maybe that's something for its author to look at ;-)<br>
</div>Try reading the Dialogic and Aculab documentation. Those cards used<br>
quite a bit of their DSP capability to remove the spillback of outgoing<br>
voice into their DTMF receivers. You'll find the DTMF detector in<br>
spandsp (not necessarily the ones in * or FS, which have been altered a<br>
bit) is superior to either Dialogic or Aculab's.<br>
<div class="im">> ASR - yes, maybe, but L&H's ASR1500 used to work perfectly well on the<br>
> same<br>
> hardware above back in the day. I'd be interested to see results of<br>
> testing an ASR<br>
> engine in with echo; unfortunately, most vendors appear to prohibit<br>
> the publication<br>
> of test results in their licensing.<br>
</div>L&H used to work fine with the J series Dialogic cards. The Dialogic<br>
documents go into considerable details about the echo cancellation<br>
arrangements to make that happen.<br>
<br>
Regards,<br>
<div><div></div><div class="h5">Steve<br>
<br>
<br>
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