Rank order signal processors, of which the median filter is a classic example, offer properties that are in a general way compatible with implementation and integrated circuitry. In order to expand the areas of applications of rank order signal processors, further theoretical development is required and forms the basis of this research. In particular, the attainable input-output relations will be studied from a theoretical point of view. The methods of automata theory and signal characterizations in terms of regular sets are used in an effective way to solve this problem.
