What about using g729 codec ? It requires a licence for commercial use, but the use for "educational purposes" is allowed ;-) It seems to be the best quality/bandwidth ratio available (8 kbits/s) I had a quick look : Asterisk/app_rpt has a "format g729" but no "codec g729", and the corresponding rows/columns in the translation matrix are empty. Did someone already try to install and use g729 ? 73 de TK1BI