A foldable mobile telephone includes a first housing, a second housing, and a connecting unit. The light source is configured for emitting light toward the light guide plate. A target voice is separated when received by said devices from other voice signals in a spectrum by using the calculated weighted CSP coefficient. The second-harmonic component amplitude is amplitude of a second-harmonic component having a frequency twice as high as excitation frequency. The coil through-opening surface is aligned at an angle of less than 90\xb0 with respect to the stacking direction.