Abstract: A wheel braking cylinder and an expandable chamber of a pressure modulator are connected in a spatially closed arrangement that is connected to an operator controlled master cylinder, with the chamber being interposed between the braking and master cylinders. When vehicle deceleration reaches an upper threshold, an electromagnet is actuated and the armature thereof operates to isolate the master cylinder from the chamber and expands the chamber to reduce pressure in the braking cylinder, thereby reducing deceleration. When deceleration reaches a lower threshold the electromagnet is de-energized so that force generated by the armature biasing spring acts to reduce the chamber volume, thereby increasing pressure in the braking cylinder.