having e g two switched positions as an actuator for incrementally switching over or connecting into the circuit load elements 42 of the load circuit 32 apart from the unavoidable pressure losses due to friction within the line 56 the pneumatic line 56 does not change the bellows pressure p as a load signal and actuating signal with the result that this line 56 constitutes a transmission device 38 within the sense of the invention the load circuit 32 has according to the embodiment in fig1 resistors 28 and in addition for example one or more inductors 60 arranged in series with respect to the resistors 28 with the pressure switch 58 being controlled as a function of the bellows pressure p in such a way that the pressure switch reduces the inductance as the loading increases and increases the inductance as the loading decreases for this purpose the pressure switch 58 connects the inductors 60 with respect to the resistors 28 when the loading decreases and disconnects them when the loading increases it is also conceivable to have a pressure switch 58 which has more than two switching stages and which connects or disconnects a plurality of inductors 60 arranged in series with the resistors 28 in a plurality of steps as a function of the loading to adapt the braking torque in an incremental fashion as a function of the load for this purpose the inductors 60 are bypassed by in each case one bypass branch 62 connected in parallel if a plurality of inductors.