For something that seems so easy to conceptualise, there is much to a CB. CB's I tested recently took up to 50 secs to trip at *twice* the stated current, as per the trip curve from the specification sheet. Justin > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .