A seat belt retractor with a ball type pretensioner including a pipe in which the balls are retained. The monolithic battery unit includes at least two electrochemical energy storage cells. The standardized interface module includes a plurality of elements, a subset of the elements required for function implementation and a second subset of the elements which can optionally be used to implement a function. Each deformable element has a deformation mechanism and an optical portion, the deformation mechanism and the optical portion independently imparting to the element respectively a controlled deformation characteristic and a controlled modulation characteristic. The stem includes primary engagement members to engage with complementary engagement members formed in a mounting hole of the door. The conduit extends within the hollow shaft of the intravenous pole.