Eric Bishop wrote:
Just out of interest,With 2-wire analogue line you will have echo from the hybrid at the local exchange.
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?
If the far end has a 2-wire analogue line you will have echo from the hybrid in their phone.
Whatever kind of phone is at the other end there will be echo from the acoustic coupling between earpiece and mic (in cellular phones and IP phones this is usually eliminated by a local echo canceller).
If you try to cancel these echos at your end it will only work if the path has a precisely constant length. If the path length changes (e.g. the far end is an IP phone), the echo canceller's training will keep falling apart. If the path length is constant, and the canceller well training it should do a very good job of eliminating the echo from the local analogue loop. It won't give more than about 30dB of suppression of the echo from beyond the A-law/u-law section of the link, due to the inherent distortion of the codec. It is normally necessary to suppress small residual signals to avoid hearing a weak echo from the distant phone when its user is silent.
Regards, Steve
_______________________________________________ Asterisk-Users mailing list Asterisk-Users@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
