Embodiments of the invention provide a protective cap assembly for a CIC hearing aid. The piston shoe or foot smoothly enlarges from the piston stem, thereby avoiding the concentration of stress at the interface. According to the method of the present invention, contact holes may be monitored at an in-line state when manufacturing an integrated circuit by transmitting corona charges onto a unit chip, eliminating the need to use a scanning electronic microscope, thereby preventing a reduction in yield. The piston stroke is variably adjustable via the combustion cycles of the free piston engine and the linear power generation system such that the top dead centers of each side of the piston are definable. The one or more intermediately located steps or shelves may be forwardly-offset relative to a front surface of the non-foldable support members. The system tracks the instantaneous location of each cargo carrying container with the multipurpose sensing module on board each cargo carrying container sampling the contents thereof for the presence of material selected from the group comprising nuclear, biological and chemical grade weapons material.