The present invention relates mainly to a braking system comprising a master cylinder comprising means of connection to a hydraulic braking circuit and means of connecting at least one chamber of the master cylinder to means of injecting brake fluid into said chamber. The main subject of the invention is a master cylinder (48) comprising at least one variable-volume chamber and one moving piston (207), the movement of which causes the volume of said chamber to vary, and means of connecting said chamber to a hydraulic braking circuit, characterized in that it further comprises means (217) of connection to a source (116) of pressurized brake fluid. The invention applies notably to the motor industry. The invention applies mainly to the braking industry.