| 摘要 |
PURPOSE: A circuit for controlling earphone muting of a mobile communication terminal is provided to detect that an earphone is plugged in an earphone jack, and to mute a voice amplifier of an analog BB chipset for a predetermined time, so as to automatically cut off noise while the earphone is plugged in. CONSTITUTION: When an earphone is plugged in an earphone jack(203), a comparator(204) detects the plugged-in earphone, and outputs a low signal. By the low signal, analog switches(205a,205b) are switched to the earphone from a microphone(206). A digital BB chipset(202) inputs the low signal, and transmits the low signal to an analog BB chipset(201). The analog BB chipset(201) operates a muting circuit(201c) by the low signal. A gain control circuit(201b) mutes a voice amplifier(201a) under control of the muting circuit(201c) for a predetermined time.
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