Abstract: A display device has a display panel in which patterns are impressed in conformity to the layout of a master instrument. With this display device, a pattern indicating a prescribed condition of the master instrument which is to be detected and a pattern representing a countermeasure for the prescribed condition are impressed on the display panel. Patterns related to the conditions of the master instrument which can be coped with without cutting off a power switch are displayed in a first color and patterns related to the conditions of the instrument which cannot be coped with unless the power switch is cut off are displayed in a second color. When particular conditions of the master instrument are detected, then patterns denoting the detected conditions and patterns representing countermeasures for the detected conditions are visually indicated to teach the operator to take a proper action.

Abstract: A display device according to the present invention is incorporated into an electrical machine in order to display the operating condition of the electrical machine. The electrical machine has movable parts such as doors to be opened by an operator when the electrical machine stops operating due to a malfunction. This display device schematically shows, by means of display elements, the positions of the movable parts before and after the operator moves them, and displays the elements in accordance with the condition of the electrical machine. Upon the occurrence of a malfunction in the electrical machine, the display elements on the schematic display corresponding to the faulty machine part can be displayed so as to be understood by the operator.

Abstract: An electronic copying apparatus comprises a device for holding a document to be copied, an optical scanning device for the document, a device which receives light reflected from the scanning device and forms a latent image of the document on a rotating photosensitive medium, a device for forming a toner image of the latent image, and a device for transferring the toner image on a copy paper. The document is intermittently scanned plural times, so that a plurality of the latent images of the document are formed at different positions corresponding to the respective scannings on the photosensitive medium in a continuous manner. A plurality of toner images corresponding to the plurality of latent images of the same document are transferred to a single copy paper.

Abstract: A toner concentration control device comprises a toner supply mechanism for supplying a toner to a developing device, a probe for picking up the toner in the developing agent after development is effected and a control mechanism for controlling the toner supply mechanism. The probe has parallel grooves on the outer peripheral surface thereof which constitute a toner pickup surface. An amount of toner picked up is optically detected and the control mechanism controls the toner supply mechanism based on the result of detection. By so doing, an amount of fresh toner corresponding to an amount of toner spent by development is supplied from the toner supply mechanism to a developing agent in the developing device to maintain constant the toner concentration in the developing agent in the developing device.