brake pressure buildup valves 19 and the main brake cylinder 3 this is of such a magnitude that when the main brake cylinder 3 is not operated the pressure present in front of the pressure limiting valve 41 is sufficient for automatic braking and if necessary blockage of wheels the reversing valve 40 the pressure limiting valve 42 and the check valve 44 are installed in the same manner between the cylinder 238 and the brake pressure buildup valves 19 of the brake pressure modulation valve arrangements 17 and 18 the 2 2 way valves 45 and 46 are closed in their normal positions and can be opened electrically these 2 2 way valves 45 or 46 are located between the connections 257 of the cylinders 237 or 238 and inlets 89 90 of the recirculating pumps 13 or 14 for the purpose of decoupling the secondary chambers 247 of the cylinders 237 or 238 from the storage chambers 21 or 22 the said check valves 91 or 92 are disposed between these and the 2 2 way valves 45 or 46 these check valves 91 and 92 can be considered to be part of the device 12 because the execution of anti locking operation alone renders these check valves 91 and 92 unnecessary with the use of so called free piston pumps as recirculating pumps 13 14 a black box 93 is associated with the additional device 12 the black box 93 includes means such as those.