A Programmable Digital Control System for Copying Machines

Machines whose functioning is dependant upon inputs and previous states can be controlled by a system that performs a series of compare and test operations only to determine the output states. For efficient operation such a system is directly linked to the input/output functions in the machine. At each step the controller decides to turn on/off, or do nothing to an output function. Its decision comes from machine inputs, operating mode and the correct time instant in the machine cycle. The comparison results decide the operation of the machine. Since the system has a memory it can be programmed for different functions and cause the machine which it controls to work differently. This programmability makes the controller similar to a computer. However, its main difference from a general computer is the few kinds of operations it is designed to perform. To be competitive with mini-computers in this application, the controller should be programmable; to compete with other implementations it must be cheaper to manufacture. A programmable digital controller for a Xerox Color Copying Machine is described. It is shown how the above concepts were reduced to hardware that was subsequently successfully demonstrated.