Abstract: A sorter includes a plurality of sheet receiving units, a conveyor for converying a sheet to one of a plurality of sheet receiving units which are able to come into contact with one surface of the sheet, a guide facing the other surface of the sheet for guiding the sheet to one sheet receiving unit, and a restriction device provided at substantially the same level as the conveyor for keeping the sheet from moving to the conveying means.

Abstract: A two-component type developer comprising an electroscopic fixable toner containing, as the coloring pigment, carbon black having a coloring power of 100 to 120 and a magnetic carrier is sued for developing electrostatic latent images formed on a photosensitive plate in correspondence to an imitation original and an original, and the image density of the toner image corresponding to the imitation original is detected and the toner concentration in the developer is controlled based on the detected image density. According to this development process, the toner concentration in the developer can be maintained within an optimum range based on the optical density of the toner image formed on the photosensitive plate in correspondence to the imitation original.