Cartridge motor (M3) The cartridge motor (M3) is a two-phase stepping motor, and drives the black and color toner cartridge developing cylinders. The motor rotates in the normal direction for color toner development, then the motor reverses for black toner development. The developer gear drive assembly and its associated clutches engage the proper developer drive gear based on the direction of the cartridge motor rotation. Figure 51. Cartridge motor (M3) 174 Chapter 5 - Theory of operation EN