Abstract: This invention relates to a brake pressure control valve and, more particularly, to a tractor-trailer control valve which includes a differential pressure surface relay piston that on one hand is acted upon by the control pressure from a control chamber and on the other hand by modulated pressure from a working chamber. The brake pressure control valve includes a first combination inlet and outlet valve which works together with the relay piston whereby the working chamber can be pressurized and vented via the first inlet and outlet valves. An auxiliary control chamber which is defined by the differential surfaces of the relay piston is connectable either to the working chamber or to the control chamber via second inlet and outlet valves. The pressure control surface of the relay piston is located opposite the working surface that is acted upon by control pressure in the control chamber. The pressure control surface can be enlarged by the pressure surface of the auxiliary control chamber.

Abstract: The device for heating and ventilating large-area vehicles comprises a blower and a heat exchanger which are arranged within a two-part housing which includes a base surface, which forms an entry opening for recirculated air from the passenger area and an air exit opening. The recirculated air entry opening is provided with a recirculated air entry housing, and the air exit opening leads into a distribution passage.

Abstract: Contrast is increased when reproducing originals, by using a first correcting signal for continuous-tone areas in the original and a second correcting signal which affects only line elements (narrow lines) in it. To generate a picture signal and a surrounding-area signal, an opto-electronic scanning member having a picture-point aperture and a surrounding-area aperture is provided. The diameter of the picture-point aperture is approximately equal to the width of the line elements in the original which are to be corrected.The first correcting signal is obtained from the picture signal and the surrounding area signal in a difference stage, and a selectable proportion of it is superimposed on the picture signal to increase sharpness.