Just for the record and future reference: The voltage rating is a maximum rating, which means that using higher voltage ratings is safe and a good thing to do. u1 == µ1 == 0µ1 == 0.1µ == 100n, the "factor" (nano, micro, ...) is often used instead of a decimal separator. See above. About the 78S09. IIRC the S means it can handle 2A as opposed to the 7809 which can handle 1A.