Abstract: An activation signal of a pump of a braking system is created as a function of a pressure gradient, preferably from a pressure accumulator. In this context, the switched-on time of a pulse-width modulated signal within an activation clock cycle is varied, taking into consideration the accumulator pressure gradient, in order to activate the pump. This is done by addressing a switching arrangement by way of a control unit. Activation as a function of the pressure gradient can be accomplished alternatively to or in combination with activation as a function of the generator voltage of the pump motor.

Abstract: A safety relay circuit for operating electric systems of automotive vehicles is disclosed. The circuit includes two series-connected change-over relays connecting the vehicle's electrical system to the operative voltage. The change-over relays are actuated by switches acted upon by a control circuit. The control circuit assures that the change-over relays are actuated alternatively.

Abstract: To monitor and control the pressure in the auxiliary pressure supply system of a hydraulic motor vehicle brake system, a circuit arrangement is employed which is provided with a door-contact switch (24) which closes when the driver's door of the motor car is opened and which at a pressure in the auxiliary pressure supply system (11-16) below the telltale threshold activates the hydraulic pump (11) irrespective of the activation of the ignition. Moreover, a holding circuit (25, 26, 30, D30) is provided through which, after closure of the driver's door, the hydraulic pump (11) continues to operate until the telltale pressure threshold or responding threshold is reached or exceeded.