| 摘要 |
PROBLEM TO BE SOLVED: To provide a portable telephone convenient in handling, capable of automatically controlling the illumination time length suited for the user. SOLUTION: A controller 6 comprises a memory 7, a timer 8 and a clock 9, and controls the calculation of the illumination times of a display illuminator 12 and an operating unit illuminator 15 and the turn on/off of the back light, using them. The controller 6 receives a key push down time from the clock 9 every key pushing, measures the time interval of the key push down, calculates the illumination time according to the measured time interval, and sets the result in the memory 7. The controller 6 turns on the back light upon receipt of a key push down signal from an operating unit 13, and actuates the timer 8 to measure the illumination time set in the memory 7 and turn off the back light after the set illumination time lapsed.
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