An apparatus and method for generating a code and a code using simplex codes are disclosed. A conductor-filter system includes a first conductor having thermal charge carriers, and a filter contacting the first conductor and including dielectrics for providing a filtering function on the charge carriers of one polarity. The first roller is constructed from a first material having a first density and the second roller is constructed from a second material having a second density. A fluid circulation device, such as a turbine or centrifugal pump, is operated in the return line to provide the primary motive force for circulating drilling fluid through a fluid circuit formed by the supply line and return line. The method also includes coupling at least one shroud to at least one of the plurality of rows of fan blades, such that the shroud is coupled to at least one fan blade tip extending within the same row of fan blades, and coupling at least one row of rotor blades to the shroud, such that the rotor blades extend radially outward from the shroud.