[Freeswitch-users] Removing echo.

Hello everyone. I know a lot about echo was said. Actually I don't understand how, when using same box with microphone, with skype there is no echo, while using sip client, echo is quite loud. On the same hardware different programs acts differently. If its client's job to remove echo, then why none of tried sip clients does not remove echo? If there is a good sip client which handles echo removal in box+microphone please advise. -- Mimiko desu.