Twice the highest freq that you want to be able to reproduce from the original signal. Bandwidth has nothing to do with it, IMHO. > So e.g. if you know (apriori) that your frequency is > between 1000 and 1100 Hz, it's enough to sample with 200 Hz. 2200 Hz, IMHO. Jan-Erik. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist