| 摘要 |
PROBLEM TO BE SOLVED: To reduce a call tone or silence it immediately after receiving an incoming call for reducing an unpleasant sense of surrounding people due to the call tone associated with the arrival of the incoming call of a portable telephone set. SOLUTION: The portable telephone set having a function of informing an incoming call by a call tone, is provided with a vibration sensor 4 that detects vibration and a tone volume control means 3 that reduces or silences a tone volume of the call tone. When the call tone is produced attended with the arrival of the incoming call, the vibration is given to the set externally so that the vibration sensor 4 detects the vibration and the tone volume control means 3 controls the call tone volume to be smaller or silenced.
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