FIELD: automatic control equipment, in particular, braking systems of vehicles. SUBSTANCE: device has piston assembly which pressurizes switching chamber, which is loaded with output pressure, from pressure decrease chamber which is connected to output chamber. In case of lack of tightness between switching chamber and pressure decrease chamber, complete pneumatic or hydraulic system can lack pressure. Goal of invention is achieved by introduced constrictor which is located between pressure decrease chamber and output chamber. EFFECT: possibility to keep full, or at least emergency pressure along complete pneumatic or hydraulic system. 2 cl, 3 dwg
