Abstract: A pressure supply system for the generation of the auxiliary pressure of a hydraulic brake system for motor vehicles comprises an accumulator, a hydraulic pump driven by electromotive force and a pressure switch (1) controlling the turning on and off of the hydraulic pump. The pressure switch (1) includes a switch piston (2) having a piston rod (5) mechanically actuating in a pressure-responsive manner, successively, two or three switches (8,9,10). The pump motor (26), by way of these switches, and by way of a relay, is turned on when a bottom pressure limit value (P.sub.U) is reached, and turned off when the upper pressure limit value (P.sub.O) is reached and exceeded. A holding circuit is connected in the electric circuit, in which are provided the switches (8,9,10) of the pressure switch (1), which holding circuit ensures an abrupt switch-over of the relay into the other switching position when a slow approach of a pressure (p) to the pressure limit values (p.sub.U, P.sub.

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: Disclosed is an electric switching device for monitoring the operation of a hydraulic brake system for automotive vehicles of the type including a brake slip control device. The electric switching device includes a first switch for switching the brake slip control device on and off, a second switch operating a warning lamp, a third switch for controlling a hydraulic pressure pump and a pressure responsive actuating element for actuating the switches dependent on the state of pressure on the brake system. Improved reliability is provided for by including functional redundancy of the first switch into the circuitry including a diode connecting a make type first switch to a break type second switch whereupon the brake slip controller circuit is grounded upon a fault condition in the controller circuit to prevent false signals from reaching the controller.