| 摘要 |
PURPOSE: A method for controlling automatically an audio output level is provided to control automatically an output level according to impedance of a headphone by using a test signal to check internal impedance of a connector for receiving an audio signal. CONSTITUTION: An optical pickup portion(111) reads data from an optical disc(110). A regeneration signal processing portion(112) processes the read data as regenerating signals. A micro-controller(116) is used for controlling operations of components according to an input signal received from a key input portion(114). An output level controller(113) is used for controlling levels of regenerated audio data of the regeneration signal processing portion(112). A D/A converter(114) is used for converting digital audio data to analog audio signals. An amplifier(115) is used for amplifying the analog audio signals of the D/A converter(114). A resistance(R1) is connected between the amplifier(115) and an output terminal of a headphone(120). A rectifier(118) is used for rectifying a voltage level of the output terminal of the headphone(120). An A/D converter(117) is used for converting the analog signals of the rectifier(118) to the digital data.
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