Abstract: A sensor senses the height of a stack of sheets in a magazine. The sensed height is scaled according to the thickness of individual sheets to determine the number of sheets available. At the start of a run of, for example, a copying machine, the number of sheets available is compared to the number of sheets required to complete the run and, if the number available is insufficient, an indication of this fact is given to the operator and an inhibit device may prevent operation of the copying machine. In one embodiment, a counter causes a sampling circuit to determine and display the number of sheets available at predetermined intervals, preferably at the beginning and end of each run.

Abstract: The light emission of a gas-discharge lamp is controlled effectively by the action of a cooling organ making use of a Peltier element having its cold side thermally connected with a portion of the wall of the lamp and having its hot side thermally connected with means for discharging heat to the ambient, together with means for sensing the temperature at said wall portion and for regulating correspondingly an electrical current to the Peltier element.

Abstract: In a process and apparatus for fixing thermoplastic image material onto paper, wherein the image material in thermally softened condition is transported through a pressure zone while being pressed between and in contact with the paper and belt moving together through said zone, and upon leaving said zone the paper and belt are separated from each other by forced movement of the belt along a path curved away from the paper, the fixing of the image material to the paper is achieved reliably in a simple manner, with little sensitivity to variations of temperature or of the character of the belt surface, by maintaining the thickness of the belt, the speed of movement of the belt and the radius of curvature of said path in a relationship defined by the formula: (D .times. V/R).gtoreq. 0.05, in which D represents said thickness (in meters), V represents said speed (in meters per second), and R represents said radius (in meters).