A continuous, progressive, flexible closure formed with rows of opposed keys whose engagement and disengagement is normal to the plane of closure. A first pixel column is arranged alongside the first data line and the second data line and the first pixel column includes a first pixel and a second pixel. The control apparatus in the control loop comprises a molten metal level senser, an FFT analyzer, an automatic tuning device for dealing with the results of the FFT analysis, a molten metal level controller and a notch filter. The packets are provided to a plurality of parallel packet transform processors and the packets are processed utilizing the packet transform processors. A protective heat-resistant layer is detachably adhered on the pre-stretched resistance element. As the result, the generation of unwanted thermal noise can be prevented.