[Asterisk-Users] Why echo occurs

[Steve Underwood]

Robert Hajime Lanning wrote:

><quote who="Eric Bishop">
>  
>
>>Just out of interest,
>>
>>When echo occurs (the type where I hear myself echoing as I talk) what
>>is bouncing against. Is it the other caller's equipment, the central
>>office or something in between?
>>    
>>
>
>When you are talking via 4 wire or VoIP phones there is a seperate
>outbound audio channel and inbound audio channel, niether the twain
>shall meet....  no echo
>  
>
Wrong. Look at any cellular phone or IP phone. They all have echo 
cancellers. If you switch these cancellers off the results are generally 
bad. What they need to remove is the acoustic spill from the earpiece to 
the mike. This can be a surprisingly strong signal.

Regards,
Steve