Extra filtering is provided on our products for two reasons. First, it enhances the operation of the product by ensuring a clean DC voltage and minimal EMI. Second, input filtering is essential to deal with spikes and surges at the input. Some of our DC converters have been qualified for use in railway applications where very severe transient conditions occur, often in the range of hundreds of volts. Input filtering absorbs much of these transients, reducing stress on the converter and enhancing reliability.