Device for controlling the unwinding of an actuation cable of an airbag, comprising a main body inside which a movable element and a locking system of the movable element are housed, wherein - the movable element is arranged rotatable in said main body and comprises: - winding devices, arranged on a first surface of said movable element, and configured to wind and unwind the actuation cable; and - a retaining device arranged on a second surface of said movable element and configured to hold an end of the actuation cable; and wherein - the locking system of the movable element comprises: - a crown element integral with the main body and having a profile provided with a plurality of recesses facing a second surface of said movable element, said second surface being arranged at an end of the movable element opposite the first surface; and - a blocking assembly, arranged on said second surface of the movable element; and wherein said blocking assembly comprises: - a helical spring which works in compression and has at least one central portion free from constraints; - a shaped element hinged to the movable element, said shaped element comprising an engagement section, adapted to engage in said recesses, and a housing seat in which a first end of the helical spring is constrained, the housing seat being arranged such that, during the winding and unwinding of the actuation cable, the thrust of the spring on the seat maintains the engagement section distant from said recesses; - a matching element in which a second end of the helical spring is constrained. - the movable element is arranged rotatable in said main body and comprises: - winding devices, arranged on a first surface of said movable element, and configured to wind and unwind the actuation cable; and - a retaining device arranged on a second surface of said movable element and configured to hold an end of the actuation cable; and wherein - winding devices, arranged on a first surface of said movable element, and configured to wind and unwind the actuation cable; and - a retaining device arranged on a second surface of said movable element and configured to hold an end of the actuation cable; and wherein - the locking system of the movable element comprises: - a crown element integral with the main body and having a profile provided with a plurality of recesses facing a second surface of said movable element, said second surface being arranged at an end of the movable element opposite the first surface; and - a blocking assembly, arranged on said second surface of the movable element; and wherein said blocking assembly comprises: - a helical spring which works in compression and has at least one central portion free from constraints; - a shaped element hinged to the movable element, said shaped element comprising an engagement section, adapted to engage in said recesses, and a housing seat in which a first end of the helical spring is constrained, the housing seat being arranged such that, during the winding and unwinding of the actuation cable, the thrust of the spring on the seat maintains the engagement section distant from said recesses; - a matching element in which a second end of the helical spring is constrained. - a crown element integral with the main body and having a profile provided with a plurality of recesses facing a second surface of said movable element, said second surface being arranged at an end of the movable element opposite the first surface; and - a blocking assembly, arranged on said second surface of the movable element; - a helical spring which works in compression and has at least one central portion free from constraints; - a shaped element hinged to the movable element, said shaped element comprising an engagement section, adapted to engage in said recesses, and a housing seat in which a first end of the helical spring is constrained, the housing seat being arranged such that, during the winding and unwinding of the actuation cable, the thrust of the spring on the seat maintains the engagement section distant from said recesses; - a matching element in which a second end of the helical spring is constrained.