| 摘要 |
A buffer memory, an electrically erasable and writable ROM, a capacitor for holding a voltage, and a voltage detection circuit for detecting the voltage of a battery for a power source are provided in a portable telephone unit. During conversation, data to be saved is written into the buffer memory. At the time of ending the conversation, the data written in the buffer memory is transferred to a ROM and written therein. When the voltage detection circuit detects that the voltage of the battery is unobtainable, the buffer memory and the ROM are operated and the data written in the buffer memory is also transferred to the ROM and written therein by the voltage held in the capacitor.
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