Hey Jeff… Everybody else has done a great job of explaining all this but while your on this subject the other piece that will help make all the “magic” less “magical” with voice channels on T1 is PCM. PCM Hope that don’t make your head spin too bad but it will help make this part “the required digital sampling rate is 8,000 Hz” make sense.

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Bryan
LEC Provisioning Engineer
Cars -n- Guitars Racin' (retired racer Oct.'07)