| 摘要 |
PURPOSE:To prevent a talking time display from being deviated from an actual talking time by backing up clock information on the occurrence of momentary interruption of a power supply. CONSTITUTION:The telephone set is provided with a backup power supply section 4 continuing power supply regardless of momentary interruption, a display section 3 displaying a talking time of the telephone set, a RAM 12 storing the display content to the display section 3 and a timer 14 counting a talking time. Then an IO 13 is provided, which gives the result of time count by the timer 14 to the RAM 12 and is an input output means to give the result of output of a clock circuit section 2 to the RAM 12 on the occurrence of momentary interruption of the power supply of the telephone set. The RAM 12 and the clock circuit section 2 are backed up by the backup power supply section 4 and the content of the RAM 12 is backed up even during the momentary interruption and the counter of the clock circuit section 2 is in operation. Thus, even when momentary interruption takes place during the talking, the deviation of the talking time display from the actual taking time is prevented.
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