[Asterisk-Users] FX-200 VOIP PORT CONVERTER FXS to FXO

[Rich Adamson]

> > Having spent 21 years in a telephone company as an engineer, reversing
> > tip & ring will have zero impact on any 2-wire fx pstn line. The equipment
> 
> Why in some cases does it infact fix the echo issues?

Because whatever the imperfection happens to be, its less noticable by
the echo cancel function. It sort of one method that helps to cover up
the problem in a few cases, but doesn't solve the original root-cause 
problem, and certainly is not going to fix every other problem. It's not
a lot different then playing with transmission levels; one can reduce
levels and the "perceived" amount of echo decreases, however the cause of
the echo problem is still there and really needs to be identified and
resolved.

It would actually be kind of fun to troubleshoot some of these cases to
get to the real root cause, but most of us probably don't have the tools
and budgets to support that effort. Based on my past telco exerience, I'd 
guess we'd find about a half-dozen rather common causes (none of which 
relate to the quality of the x100p's, etc, which was the real point). 

I would also bet a fair amount the majority of the problems noted on this 
list are not telco related at all, but rather wiring and bridged analog 
phones that few think about as the possible root cause. (I actually have a 
rather expensive telco-provided analog phone that suddenly started causing 
echo problems one day; echo was fixed as soon as we disconnected it, but 
it took us a week to actually diagnose the problem since we were "real sure" 
it was something we did related to an asterisk cvs update.)

Rich