Abstract: In a hydraulic brake system with anti-lock control, noise is reduced during ABS control by controlling the flow rate of high-pressure fluid from the master brake cylinder (2) to the wheel brakes (15, 16). This is accomplished by placing an analog or pulse-width modulated NO valve (40) in the brake line between the connection of the pressure side of the hydraulic pump (35) and the inlet valve (20,27) to the wheel brake. By this means, only one analog or analogized valve is needed per brake circuit as opposed to two if the inlet valves were analog valves. In brake systems with traction control or electronic stability control, a shut-off valve is already present in this location. Thus replacing the existing valve with an analog or quasi-analog valve is easy.

Abstract: A circuit configuration for an anti-lock brake system, which receives input from wheel sensors positioned on the driven wheels, comprises a monitoring circuit (7) which triggers a test cycle (duration T.sub.Test) when the two wheels of a driven axle signal instability for more than a predefined time span (T) during a control cycle. By way of the test cycle, braking pressure is introduced into the wheel brake of the instantaneously slower wheel (v.sub.1, v.sub.min -wheel) of the driven axle and the reaction of the driven wheels to the braking pressure delivered is assessed.