A brake system is disclosed in the applicant's German patent application DE 10 2004 011 622 A1. The above-mentioned connecting and disconnecting device in a design of the prior art brake system is provided by a hydraulic cylinder-and-piston arrangement, the pressure chamber of which is connected to a pressure fluid volume take-up element by means of a closable connection and on the pistons of which a simulator housing is supported. The connection between the pressure chamber and the pressure fluid volume take-up element that is designed as a low-pressure accumulator is closed by means of an electromagnetically operable shut-off valve which is configured as a normally open switch valve. The mentioned piston is moved when the connecting and disconnecting device is tested, and the pressure rising in the hydraulic pressure chamber is measured and the corresponding pressure signal is evaluated. The testing operation can be performed at standstill in a first application of the brake pedal after the ignition has been turned on. This state can be referred to as ‘conventional mode’. Upon termination of the testing operation a change is made into the actual ‘by-wire mode’, and the change-over is executed as soon as a fully released brake pedal is detected. The brake pedal feeling imparted to the vehicle driver in the ‘conventional mode’ differs greatly from the feeling in the ‘by-wire mode’.
In view of the above, an object of the invention is to propose appropriate measures which allow changing over from the ‘conventional mode’ into the ‘by-wire mode’ and, thus, adapting the brake pedal feeling to the respective situation.