| 摘要 |
A volume controller for handsfree is provided to talk over the phone while driving by controlling the sound volume depending on the size of ring signal by detecting a ring signal in case a user does not recognize a ring signal due to traffic noise. A car audio(30) outputs a voice signal and internal signal of a speaking person. A car audio speaker(36) converts a signal outputted in the car audio into a sound wave. A handsfree set(26) is connected to a microphone, the car audio, and a speaker, and holds a mobile phone(24). A ring signal detector(32) detects a ring signal and a call termination. A volume controller(34) controls an volume output.
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