Device for controlling a brake system for a utility vehicle, having the following features: a supply port for the provision of compressed air, a service brake port for the coupling of the device to a coupling head for a trailer brake line of a trailer of the utility vehicle, the reservoir port for the coupling of the device to a coupling head for a trailer supply of the trailer, and a parking brake port for the coupling of the device a parking brake of the utility vehicle; a parking brake control valve for the provision of a parking brake function for the utility vehicle, wherein the parking brake control valve has a first parking brake control valve port, a second parking brake control valve port and a third parking brake control valve port, wherein the first parking brake control valve port is connected to the supply port and the second parking brake control valve port is connected to the parking brake port; a trailer control valve for the provision of an immobilizing brake function and a function of electric braking for the trailer, wherein the trailer control valve has a first trailer control valve port, a second trailer control valve port, a third trailer control valve port and a fourth trailer control valve port, wherein the first trailer control valve port is connected to the supply port, the second trailer control valve port is connected to the service brake port and the third trailer control valve port is connected to the reservoir port and wherein the trailer control valve has a parking brake piston which is arranged in displaceable fashion in order, in a manner dependent on a state of aeration of the fourth trailer control valve port, to control an aeration of the second trailer control valve port via the first trailer control valve port for the provision of the immobilizing brake function and the function of electric braking; and a switchable valve means for the switchable connection of the supply port to the third parking brake control valve port and/or to the fourth trailer control valve port in order to effect the provision of the parking brake function for the utility vehicle and the provision of the immobilizing brake function and the function of electric braking for the trailer. a supply port for the provision of compressed air, a service brake port for the coupling of the device to a coupling head for a trailer brake line of a trailer of the utility vehicle, the reservoir port for the coupling of the device to a coupling head for a trailer supply of the trailer, and a parking brake port for the coupling of the device a parking brake of the utility vehicle; a parking brake control valve for the provision of a parking brake function for the utility vehicle, wherein the parking brake control valve has a first parking brake control valve port, a second parking brake control valve port and a third parking brake control valve port, wherein the first parking brake control valve port is connected to the supply port and the second parking brake control valve port is connected to the parking brake port; a trailer control valve for the provision of an immobilizing brake function and a function of electric braking for the trailer, wherein the trailer control valve has a first trailer control valve port, a second trailer control valve port, a third trailer control valve port and a fourth trailer control valve port, wherein the first trailer control valve port is connected to the supply port, the second trailer control valve port is connected to the service brake port and the third trailer control valve port is connected to the reservoir port and wherein the trailer control valve has a parking brake piston which is arranged in displaceable fashion in order, in a manner dependent on a state of aeration of the fourth trailer control valve port, to control an aeration of the second trailer control valve port via the first trailer control valve port for the provision of the immobilizing brake function and the function of electric braking; and a switchable valve means for the switchable connection of the supply port to the third parking brake control valve port and/or to the fourth trailer control valve port in order to effect the provision of the parking brake function for the utility vehicle and the provision of the immobilizing brake function and the function of electric braking for the trailer.