PORTABLE TERMINAL DEVICE

PROBLEM TO BE SOLVED: To provide a portable terminal device allowing key input during operation of an I/O device without lowering using efficiency of a power source battery. SOLUTION: In this portable terminal device provided with various kinds of I/O devices 1 and a click sound producing means 4 producing click sound in a key 7 inputting time and driven by means of a battery 6, a sound controlling means 23 controlling the volume of sound produced from the click sound producing means during the operation of the I/O device is arranged. Even when key input is carried out during the operation of the I/O device, the volume of the click sound is controlled so that a battery voltage is not dropped below the threshold value by a voltage drop accompanying generation of the click sound, and consequently, a usage limit level of the battery voltage can be set low.