As shall be described in more detail hereinafter, the difference in distance traveled by the gear 41 (really the motor 15 a) and the encoder wheel 31, as the paddle 34 traverses the sump 33 counter clockwise from the 9:00 position (see FIG. 2,) to about the 5:00 position, is a measure of how much toner 35 remains in the sump 33, and therefore how many pages may yet be printed by the EP machine or