Braking system with three independent hydraulic circuits

A braking system of a motor vehicle, including a master cylinder providing a high-pressure source for a hydraulic fluid supplied to brake motors, the master cylinder comprising first and second pressure chambers located parallel to one another and provided with adjacent respective first and second pressure outlets, the chambers comprising cylinders in which are housed respective first and second pistons intended to slide simultaneously in a first direction toward the first and second pressure outlets to effect pressures which increase simultaneously at the pressure outlets, characterized in that the master cylinder further comprises a third pressure chamber comprising a third cylinder parallel to the first and second pressure chambers and extending in a second direction which is opposite the first direction, a third pressure outlet of the third chamber connected to at least one brake motor, a third piston capable of sliding in the first direction under the effect of an input force in order to increase the pressure at the third pressure outlet, and means for transmitting at least part of the input force to the first and second pistons, the force-transmitting means comprising at least one communication between the third pressure chamber and the first and second pressure chambers and which allows fluid in the third pressure chamber to act hydraulically on and displace the first and second pistons in the first direction.