Abstract: In a brake system the actuator pressure is controlled using a closed loop feedback system where, a system pressure, indicated by a pressure transducer is compared with a predetermined reference value. During the individual control routines, pressures corresponding operation times of inlet and outlet valves are stored in a memory. In the event of a failure of the pressure transducer, a switch is made to an open loop control mode where, starting from a previously established reference pressure, the system pressure can be read from the memory and controlled by appropriate operation of the inlet or outlet valves, to achieve the desired level.

Abstract: A sanding apparatus for a vehicle, particularly rail vehicles, has a sealed container for sand and the container is provided with a bottom wall which is permeable by air. A sand discharge pipe extends from the container through the bottom wall and has an end position in front of a vehicle wheel. An air supply line extends from a source of air under pressure and opens into a chamber underneath the bottom wall of the container. An exhaust air line has one end within the container above the level of sand when the container is full and has its other end connected to the sand discharge pipe. The flows of air through the air supply line and the exhaust air line are so controlled that at a predetermined pressure of supplied air a remaining portion of the supplied air flows through the sand discharge pipe at a rate to discharge a predetermined quantity of sand per unit time from the sand discharge pipe. Various structures are provided for regulating these flows of air.