Abstract: In a single-component developer system, the charge of the developer is controlled despite changes in relative humidity by determining or predicting the relative humidity and adjusting the bias on a device for charging said toner, such as, a toner-adder roller or doctor blade.

Abstract: A copier or printer uses the principle of single pass duplexing which produces simplex output at full machine speed and duplex output with a gap of at least one sheet between sheets. It has a duplex fuser that fuses both duplex images simultaneously. The duplex fuser has a first relatively hard roller which contacts the side of receiving sheets carrying simplex images and a soft heated roller which contacts the opposite sides of sheets. The soft roller is heated, in part, by a lamp in its center, and, in part, by heat from the first roller which is passed to the soft roller between duplex sheets. The soft roller therefore runs at a higher temperature for duplex than it does for simplex. The hard roller preferably has a thin elastomeric layer on a metal core and therefore transfers heat to its surface more efficiently and faster than the soft roller.

Abstract: An apparatus forms unfixed toner images on receiving sheets and fixes the images using a fuser having at least one heated roller. A temperature control means for the roller has a run set point and a standby set point. The apparatus monitors the formation of images. If the formation is interrupted, which would result in a skipped sheet at the fuser, set point for the fuser is adjusted toward the standby set point. The invention is particularly usable in a printer in which skip frames develop because a raster image processor is unable to form pages as fast as the printer can print pages.

Abstract: Electrostatographic reproduction apparatus has two development stations in tandem to first develop a latent image with magnetic toner so that small details, lines, and the edges of solids are developed; and to then develop the remaining undeveloped or underdeveloped portions of the latent image with non-magnetic toner to fill in the inside of the solid areas. Preferably, the magnetic toner development station has a development electrode spaced further from the photoconductor than the electrode of the non-magnetic toner development station.

Abstract: Apparatus and method for controlling the toner concentration of developer mixtures in electrostatographic devices. Light is reflected from the developer and the light reflectance ratio is converted to electrical signals by a two-path circuit. Both the gain and offset of a circuit amplifier are controllable to allow for optimum response to carriers of different reflectivities. The gain is set depending upon the desired sensitivity and the offset voltage is set to establish the output voltage at a predetermined point for the particular carrier and toner being used.

Abstract: A reproduction method and apparatus provides for the secure reproduction of confidential documents that include image portions formed with magnetic or metallic toners. The method and apparatus of the invention also provides for the production of documents such as statements with checks having bank clearing data formed with magnetic toner, documents containing magnetically bar coded data, and documents recorded with either or both magnetic or nonmagnetic toner that may be distinguished when copied in accordance with a copying criterion established for reproducing secure documents.