Electronically controllable brake actuating system

Electronically controllable, antilock brake actuating system for a motor vehicle having vehicle wheels and wheel brakes, said system comprising:

• a tandem master cylinder with a primary piston bounding a first pressure area and a secondary piston bounding a second pressure area, said tandem master cylinder further including at least one simulator chamber adjacent said secondary pressure area, said simulator chamber being bounded by a simulator piston pretensioned by means of a simulator spring, said tandem master cylinder being actuated by means of an actuating pedal,
• a hydraulic chamber provided in said secondary piston,
• a nonpressurized compressive agent supply tank cooperating with said tandem master cylinder,
• an electronic control unit connected to said actuating pedal,
• brake pressure transducers controlled by said electronic control unit, said brake pressure transducers being connected to said wheel brakes and being connectable with said tandem master cylinder by means of hydraulic linkages lockable by valve devices,
• at least one sensor device recognizing driver's desired deceleration and connected to said electronic control unit, and
• said simulator piston being guided in and sealing said hydraulic chamber provided in said secondary piston against compressive agent flow in an actuation direction of said primary and secondary pistons, said hydraulic chamber being connected to said nonpressurized compressive agent supply tank.