Color CRTs, used in large display screens, have a plurality of three color electron beams that are strongly focused so that they crossover and become divergent in both the X and Y axes if the CTR’s face. The moving part and the amplitude control spindle reciprocate at a frequency approximately equal to the resonance frequency of the linear oscillator. The biaxially stretched polyolefin film has a length and a width and substantially non-absorbing and non-scattering for at least one polarization state of visible light. A method for operating the retractable ventilation system is also described. In a second operating mode, the second feeding line contributes to a second, sinusoidally varying E-field in the second slot between the edges of the second and third patches. The second spring may be formed into a pocketted spring prior to insertion into said first spring.