Abstract: An apparatus which includes a plurality of heating elements to fuse a powder image onto a copy sheet. Selected heating elements of the apparatus are energized in an ordered sequence corresponding to the surface area of the powder image being fused.

Abstract: An electrometer having reduced spacing sensitivity, with the electrometer including a probe with a charge receiving sensor element and a surrounding shield. A voltage equivalent to that sensed by the probe element is fed back to the shield to render the electrometer substantially spacing insensitive. A duty cycle control regulates the width of electrical pulses to a power transformer whose output is fed back to the probe shield to maintain the spacing insensitivity. Means are also provided to automatically test and calibrate the electrometer prior to use.

Abstract: A video amplifier for use in a document scanning system to provide signals representative of the information content of a scanned document. The amplifier includes an automatic background control portion and an automatic black level adjustment portion to maintain the integrity of the output voltage range independent of the background of the scanned document and throughout the period of time required to scan the entire document. In addition, circuitry is provided for varying the time constant of the automatic background control circuitry to make that circuitry respond quickly to changes of the background toward the "white" direction. Further, the normally white platen back is provided with a gray leading edge to prevent the automatic background control circuitry from being upset by initial runs of white in the event of an imperfectly registered non-white document.

Abstract: An electrometer system particularly adapted for non-contact measurement of electrostatic charges in electrostatography, such as the charge level on photoreceptor surface areas in xerographic machines. The electrometer circuit has a very high impedance normally floating input, and a simple D.C. measurement circuit. The measurement circuit output can be read by a conventional test meter. The electrometer is controlled by a simple switching arrangement providing an automatic zeroing position in which the initial level of the input circuit is automatically reset by a feedback amplifier from the output to compensate for any temperature induced or other variations in the measurement circuit. The power supply voltage is automatically monitored and the output meter is driven to a non-zeroing position in response to a low supply voltage.