[Asterisk-Users] Echo in CAPI channels

[Peter Svensson]

On Fri, 29 Oct 2004, Derek Conniffe wrote:

> I'm telephone company connections only (due to only having a 64Kbps 
> fixed internet connection).
> 
> Its definitely relating to the far end because it only happens when I'm 
> talking to a person using an analogue line on the far end but the 
> question asked by Robert Rozman a couple of hours ago is quite 
> interesting: how come the echo doesn't happen with other ISDN telephone 
> equipment and only with Asterisk?  I've been using ISDN for years now 
> and the first time I ever heard any echo was with Asterisk.  Unless you 
> are right about the echo only being noticable because of the additional 
> delay by having Asterisk in the system (I'm running Asterisk on a 
> Pentium III 500Mhz with SCSI disks and the server doesn't do anything 
> else in life) this could be it.

What do you have in your end was what I meant. What do you talk in? An
isdn phone? A pots phone? Those are really the only two options where you
do not have an added delay (actually, the zaptel cards add 1ms delay if
the call is cross-connected between cards). If you use a voip technology
phone such as a softphone or a hard ip phone you will have at an absolute
minimum an additional 40ms round trip time, but more realisitcally twice 
that at least. That moves the echo from the sidetone to actually being 
perceived as an echo.

Peter