An agitator motor assembly is removable from a front of an ice dispenser for servicing, thereby eliminating the need to gain entrance into a storage bin to uncouple the agitator motor assembly from an agitator bar assembly. Each of the abutting flanges has an engagement surface and an engagement member, which engages the mounting structure. This invention makes use of orthogonal ejection of ions with a narrow range of mz values to produce a ribbon beam of ions that are injected into the collision cell. When complementary colors are generated by mixing pixels in the horizontal transfer path, they differ even in the same column, thereby making it possible to prevent a false signal from being generated. The challenge items are intended for use in a computing system that discriminates between humans and text to speech system.