Control device for controlling at least the parking brake of a towing vehicle of a towing vehicle/trailer combination, said parking brake comprising at least one spring brake cylinder, and for controlling the service brake of a trailer of the towing vehicle/trailer combination, containing at least the following: a) a compressed air supply port which can be connected to a compressed air storage reservoir, b) an air quantity boosting valve device, the inlet (9.2) of which can be connected to the compressed air supply port and the outlet (9.3) of which can be connected to a working port to the at least one spring brake cylinder, and which has a pneumatic control input (9.1) for supplying a control pressure for controlling the pressure at the outlet (9.3) of the air quantity boosting valve device, c) an electrically actuatable bistable valve with an inlet (5.1) which can be connected to the compressed air supply port and to an outlet (5.2) which can be connected to the control input (9.1) of the air quantity boost valve device, wherein the outlet (5.2) can be connected either to its inlet (5.1) or to a pressure sink (5.3), d) an electronic control unit which is electrically connected to the bistable valve and which controls the bistable valve, e) at least two ventilatable or evacuatable ports (29.1, 29.2) for a trailer control valve device controlling the service brakes of the trailer, wherein in parked state of the vehicle, the one port (29.1) of the ports (29.1, 29.2) is ventilated and the other port (29.2) of the ports (29.1, 29.2) is evacuated, and that in a driving state of the vehicle the one port (29.1) and the other port (29.2) are ventilated, wherein f) the inlet (5.1) of the bistable valve is connected to the one port (29.1), characterized in that g) the outlet (5.2) of the bistable valve is always directly connected to the control input (9.1) of the air quantity boosting valve device, and h) a valve device (7; 7') is provided which can be at least partly controlled electrically by the control unit and is configured such that it connects the other port (29.2) to the inlet (5.1) or to the outlet (5.2) of the bistable valve, or alternatively to a pressure sink (7.12'). a) a compressed air supply port which can be connected to a compressed air storage reservoir, b) an air quantity boosting valve device, the inlet (9.2) of which can be connected to the compressed air supply port and the outlet (9.3) of which can be connected to a working port to the at least one spring brake cylinder, and which has a pneumatic control input (9.1) for supplying a control pressure for controlling the pressure at the outlet (9.3) of the air quantity boosting valve device, c) an electrically actuatable bistable valve with an inlet (5.1) which can be connected to the compressed air supply port and to an outlet (5.2) which can be connected to the control input (9.1) of the air quantity boost valve device, wherein the outlet (5.2) can be connected either to its inlet (5.1) or to a pressure sink (5.3), d) an electronic control unit which is electrically connected to the bistable valve and which controls the bistable valve, e) at least two ventilatable or evacuatable ports (29.1, 29.2) for a trailer control valve device controlling the service brakes of the trailer, wherein in parked state of the vehicle, the one port (29.1) of the ports (29.1, 29.2) is ventilated and the other port (29.2) of the ports (29.1, 29.2) is evacuated, and that in a driving state of the vehicle the one port (29.1) and the other port (29.2) are ventilated, wherein f) the inlet (5.1) of the bistable valve is connected to the one port (29.1), g) the outlet (5.2) of the bistable valve is always directly connected to the control input (9.1) of the air quantity boosting valve device, and h) a valve device (7; 7') is provided which can be at least partly controlled electrically by the control unit and is configured such that it connects the other port (29.2) to the inlet (5.1) or to the outlet (5.2) of the bistable valve, or alternatively to a pressure sink (7.12').