Digital data signals at a variable input frequency are converted by a numerically controlled oscillator and an interpolator to a signal at a fixed output sampling frequency. The method includes defining, as a single resistive element, a portion of a resistive film formed over a first linear conductive film formed at a position at which a first resistance value is detected when an electric contact is slid thereto, and a second linear conductive film formed at a position at which a second resistance value is detected when the electric contact is slid thereto. In another embodiment, a reference level voltage utilized in an amplifier with dual-gate transistors can be adjusted during a calibration sequence, and may be substantially unchanged from its nominal value outside of the calibration sequence. A first oxide layer is formed on a sidewall and bottom of the gate conductive layer, and a second oxide layer is formed on a surface of the substrate. A vaporizing gas that vaporizes foreign matter attached to an internal surface of the turbo molecular pump is supplied toward the foreign matter. The color calibration processor may compute such a transformation parameter set for selected pixels in the pixel array.