31 nor the check valve 32 is activated so that hydraulic fluid is again admitted into the hydraulic chamber 13 during the pressure modulation the pump 35 is at least sometimes activated to convey hydraulic fluid which has been discharged into the low pressure store 36 back into the brake line bl to perform automatic brake functions i e brake functions which are independent of driver actuation such as esp the electronic control unit ecu firstly activates the transfer valve 33 the check valve 34 and the pump 35 by way of the control signals s 3 s 4 and s 5 thus the suction side of the pump 35 is connected to the reservoir 37 of the brake pressure transmitter unit 30 so that it can remove hydraulic fluid there to introduce it into the hydraulic chamber 13 of the wheel brake rb by way of the brake line bl as a result of the open check valve 32 if pressure modulation is also required here this can take place as described above on the part of the electronic control unit ecu by further activating the transfer valve 31 and the check valve 32 by way of the control signals s 1 and s 2 information relating to the operating conditions of the vehicle which is collected by corresponding sensor means not illustrated in more detail is supplied by way of input signals e 1 to the electronic control unit ecu for processing this includes the speeds of the rotary elements 16 or the associated wheels of the vehicle to detect amongst other things whether the vehicle is stationary the gradient of the road on which the vehicle is.