A luminance component of a video signal is modulated in a first frequency band. The device is provided with a display screen for the display of the visual data andor speakers for the sounding of the audio data. To use the laptop computer, the display unit is opened to form a desirable angle with the operation face of an input part on the base unit. When the first and second white line candidates are within a predetermined range and when a ratio of contrast of the first white line candidate to that of the second white line candidate is less than a predetermined value, the apparatus decreases the certainty factor of the first white line candidate. The spool is made of material having a lower thermal expansion coefficient than material of the valve body.