Abstract: Control over the placement of image edge location on the photoconductor of an electrophotographic machine providing for a range of discharge levels for edge picture elements (PELS) which vary from greater than, to less than, that level used for fully discharged PELS. Such control is achieved independently of machine parameter control by altering edge PEL illumination intensity in accordance with data representing desired edge PEL intensity as the photoconductor sensitivity changes. A system for measuring and controlling the fully discharged PEL level establishes a measurre of photoconductor sensitivity and is used for enabling the selection of current edge PEL intensity.

Abstract: A copier fuser roll's temperature is accurately maintained by supplying selected half-cycles of current from a power supply to a heater in accordance with signals from a temperature sensor. Each sequential half-cycle is assigned a unique digital input number which accesses a table of digital output numbers having values chosen to correspond to one or more half-cycles. Sensor signals are sampled and digital temperature error numbers, determined by the fuser roll temperature and a desired roll temperature, are derived. The temperature error and output numbers are compared and, whenever a comparison occurs, the corresponding half-cycle of current operates the heater. Thus, depending upon the difference between a desired and the actual roll temperature, variable numbers of evenly spaced complete half-cycles, having a total positive-to-negative ratio approaching unity, are selected.

Abstract: A circuit providing digital representation of an analog error voltage present as an output of a bridge circuit where the digital representation is independent of supply voltage variations to the bridge circuit. The circuit shows a capacitor designed to ramp from an initial voltage representative of the zero point of the analog error voltage range to a full-scale error voltage in the amount of time it takes for a digital counter to count from zero to full scale. The ramping voltage is compared to the error voltage in order to decode error count whenever the ramping voltage reaches a value just in excess of the error voltage.