High-voltage Power Distribution Figure 5-2 Engine Controller Board In response to the instructions from the microprocessor (CPU:IC 501) on the Engine Controller Board, this circuit applies the superimposed voltage of DC voltage and AC voltage to the primary charging roller and Developing Cylinder, and a positive or negative DC voltage to the transfer charging roller. According to the image density information sent from the Formatter, this circuit varies the primary DC bias and developing DC bias to adjust the image density. 5-4 Functional Information