Hydraulic braking systems for vehicles

A power system for a vehicle comprising at least one pressure converter which takes energy from one system at a first pressure and converts said energy into energy at a second pressure in a second system, said pressure converter being operative when said one system is operative, a power source of hydraulic pressure fluid for supply to said pressure converter, a sub-system provided with hydraulic fluid which is adapted to be pressurised by said pressure converter, said fluid supplied to said converter by said power source being separated from said hydraulic fluid of said sub-system by said pressure converter, a booster operable in response to pressure in said sub-system, for providing an output pressure, a master cylinder to operate ancillary equipment, said output pressure being augmented by said pressure converter by means of a force generated by said booster in response to said pressure in said sub-system, and an hydraulic accumulator incorporated in a line between said converter and said booster.