> So R2 and D3 in this configuration functions as a stable voltage regulator to the base of Q1. > Am I close? Right on target. Next (small) step: that stable voltage feeds the basis of Q1, who in turn feeds the 10F chip. Why this Q1, why not feed the chip directly from D3? Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: www.voti.nl consultancy, development, PICmicro products docent Hogeschool van Utrecht: www.voti.nl/hvu -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist