The system is characterised by a front axle brake valve unit (80) which includes first and second selector valves (110,111) having a respective first inlet (110a,111a) connectable in operation to a first pressure source (71), a respective second inlet (110...

The valve unit (50) is for use in a braking system of a tractor unit, for controlling the braking of a towed vehicle. It comprises valve devices (70, 90, 64) with a single piston (70) which can perform an operative movement between a rest position and a fl...