[Asterisk-Users] Still unacceptable echo on X101P

[Kevin Walsh]

Rich Adamson [radamson at routers.com] wrote:
> > 3. If impendance mismatch is the (or a major contributing) factor, can
> > we not devise some interface circuit which will allow a variable rate
> > on the impedance so we can "dial out" the echo based on individual line
> > conditions?
> >
> That would be called the TDM card. It has a chipset that was designed
> to match telco standards in many (if not all) countries. In Canada,
> if you have x100p echo problems, you'll have them with the tdm card
> as well.
> 
> You'll find plenty of discussion in the archives relative to x100p/tdm
> echo problems unrelated to impedence mismatches. Seems there is an issue
> with interrupt latency, pci controller, or something like that associated
> with some motherboards that "is" impacting echo (as well as other things).
> 
> Multiple individuals have found that replacing their motherboards fixed
> the echo problem with these cards, but no one (as yet) as put their
> finger on why with any degree of accuracy. Lots of opinions, but no
> real facts to date.
> 
> [snip]
> 
> There is a high probability (but this is a wild guess) the echo issue
> has something to do with the specific chipset used by the motherboard
> manufacturer, and if that guess is correct, probably something to do
> with how interrupts are handled or pci controller issues, etc.
> Something on certain motherboards seem to be delaying the transfer of
> data to/from x100p/tdm cards, and that delay is sufficient enough to
> fall outside the limits of the echo cancellation software within *.
> 
You could go to a lot of time, effort and expense buying a TDM card,
fitting a new motherboard (PCI 2.2), fiddling with gains and trying
all of the other suggestions that have been posted, or you could just
buy an external FXO device, such as a Sipura SPA-3000, and expect it
to just work.

External devices are not sensitive to PCI latency and are not
concerned with the brand of motherboard you use.  All facilities,
such as echo cancellation, are provided onboard rather than via a
software driver.

I don't have echo problems on my X100P (at home) but that won't stop
me from dumping it in favour of a Sipura SPA-3000 next month, once it
gets full UK support in firmware (caller ID etc.).

-- 
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