| 摘要 |
PURPOSE:To share a sound electric power amplifier circuit by providing an inner sound attenuating means for attenuating an inner sounc outputed from a radio tuner part/cassette reproducting part and a signal path for introducingan outer sound signal supplied to an outer cound input terminal to an amplifier. CONSTITUTION:When a warning voice signal is supplied to the outer input terminal 2b of a car audio part 2, it supplies said signal to the inversion input terminal 13c of an arithmetic amplifier 13 through a coupling capacitor 24 and a resistance 25, and simultaneously supplies said signal to the base of a transistor 27 through a resistance 26. A DC voltage is supplied to the arithmetic amplifier 13 and a sound electric power amplifier circuit 14 through the collector of a transistor 9. When the cassette reproducing part 11 is in the off-state, only the warning voice signal introduced to the arithmetic amplifier 13 is amplified to be outputted in a sound from a speaker 23. When the cassette reproducing part 11 outputs an audio signal, it is voltage-divided by resistances 16 and 32, and the attenuated audio signal is supplied to the inversion input terminal 13c of the arithmetic amplifier 13. |
