Hydraulic braking system comprising an improved control member

The system (10) has a pneumatic servomotor (14) for assistance of braking of a master cylinder (16) hydraulically connected to a rebound clip (20). A regulator body (42) comprises a pneumatic chamber (44) with a conduit (80) connected to a pressure source for coaxially communicating with a seat (64). The pneumatic chamber supplies pressure greater than another pressure (P1) to another conduit (52) when a socket (58) occupying a position associated with a reduced pressure in a chamber (72) of the master cylinder closes a third conduit (48) through its face (62).