Steve Underwood wrote:

When there is Echo being generated from the far end, usually in a 
bridged call. If you application is just an IVR, with no far end 
connectivity, then you shouldn't need an echo can. If you are bridging 
calls, then at some point you may need it, depending on what else is 
in the loop.

This is VERY VERY WRONG. IVRs badly need echo cancellation. Without it 
they give very poor reliability detecting DTMF while the prompts are 
playing. If the system uses voice recognition, its reliability will be 
even worse.

With respect, this is at best half true. DTMF detection has always worked just fine
without echo cancellation - the Dialogic, Aculab and Rhetorex cards which I used
in the late 1990s managed it perfectly well; if the DTMF detection code in * and FS
can't, then maybe that's something for its author to look at ;-)

ASR - yes, maybe, but L&H's ASR1500 used to work perfectly well on the same
hardware above back in the day. I'd be interested to see results of testing an ASR
engine in with echo; unfortunately, most vendors appear to prohibit the publication
of test results in their licensing.

--Dave