An electromagnetically actuatable pressure modulator for anti-locking brake systems utilizes a variable lever-type transmission interposed between a pressure relief piston of the modulator and the compression spring biased armature of an electromagnet whereby the non-linear force/air-gap relationship of the electromagnet is converted to a linear variation of the force applied to the pressure relief piston for moving same. When a predetermined maximum brake pressure is applied to the modulator, the latter automatically isolates the wheel cylinder from the master cylinder.