| 摘要 |
PROBLEM TO BE SOLVED: To provide a mobile terminal device in which Kana (Japanese syllabary) characters can easily be inputted while maintaining its portability. SOLUTION: A keyboard 110 is connected to the main body 10 of a portable telephone set via an earphone terminal 151 and a microphone terminal 153 which make up an earphone microphone jack 15. A clock signal that is generated by a clock generation circuit 115 is supplied to the keyboard 101 via a switch 113 and the terminal 153. The keyboard 110 rectifies the received clock signal to use it as its power supply and also as a synchronizing signal that is needed for generating a serial signal. The keyboard 110 is a touch key type keyboard and has a single Kana character allocated to a single key. When a key is operated, the keyboard 110 generates a serial signal of RS232C standard corresponding to the operated key and supplies the serial signal to the main body 10 via the terminal 151. The main body 10 shapes the waveform of the serial signal via a waveform shaping circuit 111 and supplies it to a CPU 112.
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