A digital signal processor employs a variable-length instruction set. The preparing step comprises preparing a multi-axis machine tool, a laser displacement meter, an auto scraping apparatus and a computer. Each of the pressure drop stages is adapted to create part of an overall pressure differential between the inlet and outlet ports. A PBMSCH transmitter transmits data of the second service through the secondary carrier by oscillating the secondary carrier as the transmission frequency. This improves the uniformity of beam current at a lithographic substrate and minimizes location-dependency of the aperture angle. If desired the roller wheel can have a roughened or slotted circumferential surface.