What is the formula to calculate the oscillating (resonant?) frequency of a series RC circuit with a constant DC voltage? For example the RC circuit shown at this site: "http://www.mikroelektronika.co.yu/english/product/books/PICbook/2_02chapter.htm" [Broken] How does this circuit resonate with a DC voltage? Aren't capacitors supposed to act like an open circuit to DC voltage? I have searched all over using google but cannot find details on RC oscillators.