Differential mode noise can usually be suppressed by connecting bypass capacitors directly between the power and return lines of the switching power supply. The power lines that require filtering may be those located at the input or the output of the switching power supply. The bypass capacitors on these lines need to be physically located adjacent to the terminals of the noise generating source to be most effective. The actual location of the bypass capacitor is critical for efficient attenuation of differential mode currents at high frequencies. Attenuation at lower frequencies of differential mode currents around the fundamental switching frequency of the noise generating source may dictate that a much higher value of bypass capacitance be required that cannot be attained with a ceramic style capacitor. Ceramic capacitors up to 22µF may be suitable for differential mode filtering across the lower voltage outputs of switching power supplies but not be suitable for the switching power supply inputs where 100V surges can be experienced. For these applications electrolytic capacitors are employed because of the high capacitance and voltage ratings. Differential mode input filters usually consist of a combination of electrolytic and ceramic capacitors to suitably attenuate differential mode current both at the lower fundamental switching frequency as well as at the higher harmonic frequencies. Further suppression of differential mode currents can be achieved by adding an inductor in series with the main power feed to form a single stage L-C differential mode low pass filter with the bypass capacitor.