| 摘要 |
PURPOSE: A car audio automatically muted in case of receiving a car phone is provided to automatically turn on and mute an audio regardless of a power switch of the audio. CONSTITUTION: A frequency converter(60) converts a signal of a bell sound generated in the case of receiving a car phone(10) and a signal of a call completing sound generated after completing a call into a direct current. A mute terminal(42) mutes an operating audio when receiving the converted signals from the frequency converter(60). A microcomputer(40) of the audio has a mode terminal(44) outputting a signal for automatically turning on the audio. A power control unit(50) of the audio automatically turns on the audio when receiving a signal from the mode terminal(44). A mute transistor receives the signal outputted from the mute terminal(42) for automatically muting the audio. The applied bell sound and the signal of the call completing sound, and transmitting and receiving sounds of the car phone(10) are output to a speaker(30) through buffers(80) and a power amplifier(90).
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