Can be broadly divided into direct action vacuum booster and hydraulic vacuum booster. Because the direct role of the vacuum booster directly assisted in the tread force, the braking operation feeling good, therefore, widely used in cars and small trucks, but because the leg directly as a help, will be limited by the installation of space. Hydraulic Vacuum Booster is the use of the main cylinder to create hydraulic power, so can be installed in the main cylinder and the wheel of any position between the cylinder, but the sense of braking operation is generally better than the direct effect of vacuum power difference.
The power source of the booster device uses the negative pressure of the engine intake manifold (petrol engine vehicle) or vacuum pump (mainly diesel engine vehicle).
A one-way valve must be added to the connection line between the booster device and the negative pressure source. The check valve can reduce the negative pressure in the booster device while maintaining a high vacuum, in addition, in petrol engine vehicles, in order to prevent gasoline inflow booster devices, generally in the engine intake manifold and booster installation between one-way valve, to prevent the hose inside the gasoline flow booster device, check valve installed in the hose of the highest point, or installed near the top of the engine.