Abstract: A device for switching a combustion engine from a propelling mode to a braking mode, wherein the combustion engine has at least one intake valve and at least one exhaust valve per cylinder, includes a cam shaft for actuating the intake and exhaust valves of each cylinder and a hydraulic linkage made of transmitting pistons and receiving pistons for connecting the cam shaft to the intake and exhaust valves of each cylinder. The cam shaft has a first intake cam for actuating a first transmitting piston and a second intake cam for actuating a second transmitting piston, the first and the second transmitting pistons controlling the intake valve, and a first exhaust cam for actuating a third transmitting piston and a second exhaust cam for actuating a fourth transmitting piston, the third and fourth transmitting pistons controlling the exhaust valves. A control system has a non-rotatable control slide connected between the transmitting and receiving pistons.