Abstract: A trailer or towed vehicle braking system incorporates a master hydraulic cylinder, the piston of which is biased to apply pressure to the slave cylinders in the braking system and wherein an electric high torque mechanism, when operated at high electric power, overcomes the biasing force to apply no pressure to the slave cylinders. When the electric power to the high torque system is reduced, the pressure applied by the master cylinder is increased. The amount of electric power applied to the high torque motor is preferably controlled based on the braking pressure being applied in the towing vehicle.