I'm in agree with all explanations regarding the echo and 2/4 wires conversion. However I'm wondering if there are other parameters like CPU and/or Asterisk configuration involved in the problem with more weight than hybrid. Otherwise how do you explain the difference in the following scenario:
1.- Crystal clear voice:
[phone1]----[pabx]-----[fxo gateway]------SIP-------[fxs gateway]------[phone2]
2.- A lot of echo:
[gnophone or xten]---[ * ]---------------SIP-------------[fxs gateway]-----[phone2]
First, I assume that the right hand side in both cases is the same. Then determine where the echo originates. I would guess that it is either coming from the fxs gateway and that there is no echo cancellation running on the fxs, while there is on the fxo, or you are using an open mic and speaker on the softphone. In the first case, when the fxo is in the circuit, the echo canceller sees the echo - it doesn't care where it comes from, the signal will stii autocorrelate because it contains a copy of itself - and it gets removed. In the other case, the echo does not get removed because the echo canceller is not running on that channel. Examine the channel status (zap show channel x) and the canceller is active when a call is in progress. In the second case, use a headset. Echo cancellers are notoriously poor at cancelling room echo very well without very compute intensive algorithms and long tail lengths (lots of taps). It usually reguires a DSP. If it's neither of these, then I am stumped.
The first scenario has four 2/4 W conversion.
Well, I only see two possible hybrids here, unless the PABX is running analog at the external ports and digital internally -nutty, but possible.
The second one has only two (or one?).
Probably one.
The * was running in differents CPU, PIII 500 Mhz, PIII 750 Mhz, 128 Mb to 512 Mb ram with not difference on echo.
We have installed a Mitel 3100 with IP phones at 40 kms within a wireless network with not echo at all.
_______________________________________________ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users
