[Asterisk-Users] Echo cancellation again ...

[Florian Overkamp]

Rich Adamson wrote:
>>I have been reading with great interest the posts on trouble shooting 
>>echo cancellation with *.  Is it just coincidence that all of this 
>>discussion has been with analog lines.  Are PRI's susceptible to echo 
>>problem like POTS lines.
>>
> 
> 
> Keep reading. Echo _can_ occur whenever a two-wire circuit is converted to
> a four-wire circuit (eg, hybrid involved). There is no way for you to identify
> where (in a pstn call) that might occur even with a PRI. You could have 
> a PRI (four-wire) leaving your facility, but the telco (or another pstn
> customer) may have a hybrid involved in that end-to-end call.

Very nice summary post. One thing to remember: If your side of the call 
is hearing an echo, it is being caused somewhere on the other side.

Also, there are two kinds of echo. Hybrid echo, which has now been 
discussed, and accoustic echo. Any echo can be batteld best at the place 
where it is caused, and this is especially true for accoustic echo. With 
accoustic echo, see if the source device (handset, speakerphone, ...) 
can be tuned properly (echocancellation settings, echosuppression or 
maybe just lowering the volume a bit).

Also note: An echo becomes more and more problematic as the round-trip 
delay time increases.

Best regards,
Florian