> B.t.w, what is "back-of-envelope" ?? It is a term used to suggest a basic sketch of a circuit on any handy writing surface. Depending on who is in the conversation a similar term is "back of cigarette packet" as a variation on the same theme. Generally used to mean doing something basic to get an idea of how something works. -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu