Abstract: Push buttons (9u, 9d) are provided to select the desired intensity of a lamp (1) for electrostatic copying or the like. The selected intensity is numerically displayed. A preset function is provided to preset the intensity to a standard value when power is first applied to the apparatus. The intensity may thereafter be manually varied using the push buttons (9u, 9d). The lamp intensity is controlled by means of phase angle control of a thyristor (2). Provision is made to compensate the phase angle control for variations in the A.C. power supply voltage.

Abstract: A control system for electrophotographic copying machines which may forcibly return the component parts which are reciprocated and rotated during the copying operations to their home positions after a power switch is turned on, may detect malfunctions after the copying operations are started and may enable the copying machine to repeat the copying sequence without the feed of copying sheets for running tests in inspections and maintenance. One or more one-chip microcomputers are used in order to control the above and other steps so that a number of component parts may be minimized and the copying machines may be made compact in size and be economically fabricated.

Abstract: A plurality of feed units feed a copy sheet (13) down a sheet feed path (41) along which various operating units (18), (37) are disposed. The operating units (18), (37) function to transfer and fix a toner image to the copy sheet (13). Sensors (42), (43), (44), (46), (47) sense for the presence of the copy sheet (13) in the feed units at respective times. Absence of the copy sheet (13) indicates that the copy sheet (13) is jammed or stopped in the previous feed unit. In such a case, all feed units downstream of the feed unit in which the jam is sensed are driven to feed out prior copy sheets (13) in the downstream units. All feed units upstream of and including the feed unit in which the jam is sensed are de-energized to enable the operator to clear the jam.

Abstract: An image of an original document (16) is sensed to determine if the document (16) is a printed document (the image consists of characters and symbols) or a photographic document. The exposure illumination intensity, developing bias voltage and/or other variable operating parameters are controlled in accordance with the determination.

Abstract: A method of controlling the fixing temperature of a powder image comprises the steps of detecting electric power, which is supplied from a power source to a heating element that is contained in a powder image fixing unit to heat the image, by means of a power detector, and controlling the power supplied to the heating element in accordance with an output signal from the detector, thus preventing a variation in the fixing temperature which might result from a fluctuation in the source voltage.