Abstract: A developer unit which develops an electrostatic latent image recorded on a photoconductive member used in an electrophotographic printing machine. The developer unit uses a developer material which ages during the life of the electrophotographic printing machine. Additional developer material having at least carrier granules and toner particles, is supplied to the developer material in the developer unit to extend the life of the developer material. Discharge of developer material from the developer unit is controlled by a permanent magnet and an electromagnet positioned adjacent an exit port in the developer unit. The permanent magnet generates a magnetic flux field in the region of the exit port to form a developer material curtain which prevents the passage of developer material from the exit port. When the electromagnet is energized, it generates a magnetic flux field which attracts developer material from the developer material curtain.

Abstract: An electrophotographic printing machine in which a controller regulates charging of a photoconductive member in accordance with information stored therein. The controller determines the charging current as a function of the rest time between successive copying cycles.

Abstract: An apparatus which controls the electrical charging of a photoconductive member used in an electrophotographic printing machine. The apparatus has a pair of corona generating devices. The second corona generating device detects the level of charge on the photoconductive surface after the charging thereof by the first corona generating device. In response to the detected charge level, the second corona generating device transmits a control signal to the first corona generating device so as to regulate the charge on the photoconductive member.