| 摘要 |
An information terminal device comprises a backlight for illuminating a key operation portion or a LCD display portion; an optical sensor portion for detecting lightness of the surroundings; a backlight control for turning on illumination light according to surrounding light for a fixed time after key operation; and an optical sensor control for applying electric power to the optical sensor portion at regular intervals thereby to detect the surrounding light, wherein the application of the electric power to the optical sensor portion is forbidden except when the surrounding light is detected. Further, the backlight control switches, according to the surrounding light when the key operation is performed, control in which both the key operational portion backlight and the LCD backlight are turned on, control in which only the LCD backlight is turned on, and control in which both of the backlights are not turned on.
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