| 摘要 |
<P>PROBLEM TO BE SOLVED: To inform a host OS a setting level of an analog volume. <P>SOLUTION: A sound circuit 5 outputs a sound signal of AC voltage V<SB>1</SB>to a synthesizing circuit 9. A DC power source 8 outputs fixed DC voltage V<SB>2</SB>to the synthesizing circuit 9. The synthesizing circuit 9 synthesizes the AC voltage V<SB>1</SB>of an analog sound signal output from an audio amplifier 7 and the DC voltage V<SB>2</SB>output from the DC power source 8. The level of the sound signal (V<SB>1</SB>+V<SB>2</SB>) synthesized by the DC voltage is varied by the analog volume 10. The DC component aV<SB>2</SB>of a voltage-divided sound signal is output to an A/D conversion circuit 13. The DC component aV<SB>2</SB>of the sound signal is converted to a digital signal by the A/D conversion circuit 13, and given to the OS. By converting the DC component aV<SB>2</SB>of the sound signal to the digital signal and giving it to the OS, the OS gets to know the setting level of the analog volume 10. <P>COPYRIGHT: (C)2008,JPO&INPIT |
