Abstract: The present invention is a multiprocessor control system that allows full job recovery after a machine power down or after a malfunction or software crash or temporary power outage. In particular, essential variables such as the state and status of the machine and the programmed job at the time of the malfunction are maintained in nonvolatile memory. This information is continually updated in nonvolatile memory. Once the control system has reset and reinitialized all the control elements after a malfunction, the control restores or downloads all the relevant variables in the nonvolatile memory to the various control elements to maintain status. In another embodiment, the essential variables are maintained in RAM locations in a master processor and saved for downloading to the control elements.

Abstract: In an electrostatographic duplex copying system wherein a first image is transferable from an image support surface to one side of a copy sheet by electrical transfer fields, and the copy is then removed from the image support surface, and the first image thermally fused, and the copy sheets are then subsequently returned to the image support surface for the transfer of a different image to the other side of the sheets, duplex switching means are provided for changing the level of the net applied transfer fields for the second side transfer to compensate for changes in the characteristics of the copy sheet from the first side transfer and fusing, preferably by switching the D.C. bias level of a D.C. biased A.C. transfer detacking corona generator.

Abstract: In an electrostatographic copying system, where a common imaging surface is subjected to currents from several corona generators during copying, the actual output current of each corona generator is individually measured, and controlled, utilizing individual current measurement resistive paths between the low voltage sides of discrete power supply circuits provided for each corona generator and a common ground path from the imaging surface, and by individually feeding back the shield current of each corona generator in a feedback path separate from the current measurement path. A.C. lead feedback, and switching and measurement circuitry are also disclosed.