Abstract: Expandable memory system having add-on modules beginning at fixed address boundaries, e.g., 2K (K=1024), and having verification and authorization features. A non-volatile memory stores a bit corresponding to each 2K memory boundary. When an add-on program is authorized at a particular boundary address, the corresponding bit is set. The base program checks each bit and, if it is set, reads the first location of the corresponding add-on program. If the data read from the new module matches some reference, e.g., the boundary address itself, then program control branches to the add-on program. Additional verification features include cyclic redundancy checks of the added code. Alternative operation includes branching to a verified add-on program that tests its own authorization bit which, if reset, causes a branch to the next verified add-on program, and so on.

Abstract: Sheet collator apparatus having means for recovery from collating errors. Moving between two adjacent bins without feeding a sheet, feeding two sheets into one bin, or feeding a sheet while the feeder is moving are errors that are detected and corrected. An error is corrected by homing the deflector and repositioning it at the correct bin before restart. The described embodiment includes two collators, i.e., tandem units.

Abstract: A copy production machine controlled by a programmed computer in which the computer control programs include synchronous and asynchronous portions. The asynchronous portions are repetitively executed in loop form for checking operating components and servicing operator control panels. The synchronous portions are executed in timed relation to the operation of the machine. The execution of the programs is coordinated via a set of memory registers accessible by the computer during execution of both program portions.