Abstract: A pair of laminated metallized films is convolutely wound into a roll. The metallized area of each dielectric film is segmented into a plurality of longitudinally spaced apart metallized areas which are connected together to an electrode. The separation between successive metallized areas is in a range from 0.1 mm to 5.0 mm and the interval between successive separations is from 10 mm to 500 mm to assure a 100% guaranty. A first of the metallized areas extends transversely from a first non-metallized marginal area to the opposite edge of a first dielectric film. A second of the metallized areas extends transversely from the second non-metallized marginal area to the opposite edge of a second dielectric film. First and second electrodes are respectively connected to edges of the first and second metallized areas.