This invention provides an improved process for coating medical and surgical devices and the like using super-critical fluids. The cover has a number of parallel, aligned, projecting pins projecting from the body of the cover. The device includes logic circuitry, a mechanism for receiving a control signal associated with the logic circuitry and a selector. The control inputs to the controlled rectifiers are cross-coupled from opposite secondary transformer windings. Subsequently the semispherical RGP film is annealed to grow a crystal of silicon to form a generally spherical RGP film.