The main components of a hydraulic brake system are:
(1) Brake Master Cylinder
(2) Brake Booster (Servo Unit)
(3) Propotioning Valve (also called P-valve)
(4) Drum Brake (mostly used on rear wheels)
(5) Disc Brake (used on front wheels)
The basic concept of hydraulic braking system and how it works is simple. When the driver presses the brake pedal with the foot when needed, the Brake Booster increases the pedal force according to the Pascal law. Modern cars that did not have servo brakes required large amounts of braking force produced by the driver’s foot. A servo unit is a system that uses global air pressure to increase pedaling force. The driver just put his foot down. There are many forces that push the master cylinder.