A method of using an interface device to interface to a processing unit is disclosed. The interface device and the processing unit are part of a station of a plurality of stations in a sheet processing line. The method involves using the interface device to receive a control signal from an upstream station, and comparing a selection part of the control signal with a reference, the selection part being part of an addressing part of the control signal. If the comparison result is negative, a further control signal is determined from the control signal, which is derived from and differing from the addressing part of the control signal and the interface device outputs the further control signal to a different interface device corresponding to a processing unit of a downstream station. If the comparison result is positive, an instruction signal is sent from the interface device to the processing unit.

An image forming apparatus determines whether crease processing at a plurality of portions set on the sheet includes crease processing on two, front and back surfaces of the sheet; determines, if it is determined that crease processing includes crease processing on the two surfaces of the sheet, whether a connected post-processing apparatus that performs crease processing on a sheet can perform crease processing on the two, front and back surfaces of the sheet by one feeding; and controls, if it is determined that the connected post-processing apparatus cannot perform crease processing on the two surfaces by one feeding, to change, to one of the front and back surfaces of the sheet based on attribute information of the sheet, a surface to be processed in crease processing at the plurality of portions.

Provided is an image formation system of series tandem type in which first and second image formation apparatuses connected in series execute an image formation process on a recording material, wherein the first image formation apparatus includes: a first image carrier; a first toner image formation unit; a first density detection unit; a first density control value setting unit; and a first temperature detection unit, the second image formation apparatus includes: a second image carrier; a second toner image formation unit; a second density detection unit; a second density control value setting unit; and a second temperature detection unit, and the image formation system includes: a recording material density detection unit; and a control unit.

A digital printing system is disclosed having two independently operable printing towers arranged in series such that a substrate sheet passes sequentially through both printing towers, and in which a perfecting mechanism is provided between the two towers to reverse each substrate sheet during transfer from the first printing tower to the second printing tower, the perfecting mechanism being selectively operable to enable the second tower to print either on the same side of each substrate sheet as the first tower or on the opposite side of each substrate sheet. As well as allowing a duplex mode, the system provides a higher speed simplex mode during which different separations of the same image are printed by the two towers.

An image forming apparatus includes: a first image forming unit that includes plural first image forming sections and a first intermediate transfer member on which a toner image formed by the plural first image forming sections is primarily transferred; a second image forming unit that is provided on a downstream side of the first image forming unit in a paper transport direction and includes plural second image forming sections and a second intermediate transfer member on which a toner image formed by the plural second image forming sections is primarily transferred; a first secondary transfer section that is provided corresponding to the first image forming unit and secondarily transfers the toner image formed on the first intermediate transfer member onto paper transported on a paper transport path; a second secondary transfer section that is provided corresponding to the second image forming unit and secondarily transfers the toner image formed on the second intermediate transfer member onto paper transported on a paper transport path; and a paper position adjusting roll that transports fed paper, at a predetermined timing, to a first secondary transfer position at which the first secondary transfer section performs secondary transfer, in which a distance between the paper position adjusting roll and a second secondary transfer position at which the second secondary transfer section performs the secondary transfer is longer than a maximum paper length that is a transport-direction length of paper having a largest paper size among sheets of paper having a probability of being used.

An image forming system includes a first image forming unit including plural first image forming portions and a first intermediate transfer medium to which a toner image formed by the plural first image forming portions is primarily transferred, a second image forming unit that is provided on a downstream side of a sheet transport direction with respect to the first image forming unit and that includes plural second image forming portions and a second intermediate transfer medium to which a toner image formed by the plural second image forming portions is primarily transferred, a sheet transport portion that transports a sheet to a secondary transfer position at which each of the toner image formed on the first intermediate transfer medium of the first image forming unit and the toner image formed on the second intermediate transfer medium of the second image forming unit is secondarily transferred, and a processor configured to, in performing registration between a position of an image printed on the sheet by the first image forming unit and a position of an image printed on the sheet by the second image forming unit, cause each of one first image forming portion selected from the plural first image forming portions of the first image forming unit and one second image forming portion selected from the plural second image forming portions of the second image forming unit to form the image at the same position on the sheet, and reduce a misregistration amount by partially changing a drawing cycle of the image in any one of the first image forming unit or the second image forming unit in accordance with a relative misregistration amount between the two formed images.