| 摘要 |
PROBLEM TO BE SOLVED: To provide a portable telephone system for enabling a user to listen to speeches with a proper volume when the user uses an earphone to perform speech communication. SOLUTION: In this portable telephone system, when the user pulls an earphone microphone 2 out of a cord winding part 3 in response to a ringing tone, a rotary encoder 4 and a cord pulling out and winding detecting part 5 detect that the earphone microphone 2 is pulled out, and an earphone use signal and an off-hook signal are transmitted to a control part 7. Since the control part 7 closes a speech communication circuit and sets a volume level to a reference level stored in a storing part 10 when the earphone is used, the user can perform speech communication with a comfortable volume. COPYRIGHT: (C)2004,JPO&NCIPI
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