Trailer brake valve for trailer vehicles with electronic brake control and increased security of the parked trailer

The valve unit has a valve (8) with two hoses (30, 31), a supply connection, a brake pre-setting connection, a container connection and a brake pressure connection. When the supply connection is pressurized, the pressure at the brake pressure connection depends dependent on the pressure at the brake pre-setting connection. The first no-return valve is rendered ineffective when the supply connection has no pressure.