| 摘要 |
PURPOSE:To shorten the response time, by driving a switching circuit, which operates a control circuit, by the output of an amplifying circuit, which has a time constant longer than a region discrimination signal period, and by stopping the supply of region-classified signal pulses to the amplifying circuit by this output. CONSTITUTION:The output of an antenna 11 of an FM receiving circuit 10 is converted to sounds by a front end circuit 12, an intermediate frequency amplifying circuit 13, an FM detecting circuit 14, a low frequency amplifying circuit 15, and a speaker 16. A part of the output of the FM detecting circuit 14 is applied to a pilot selective amplifying circuit 21 of a traffic information decoder circuit 20 to take out a pilot signal SK, and the pilot signal SK is detected by a pilot detecting circuit 22. A part of the detected signal is applied to a region-classified signal selective amplifier 25, and the rest is applied to a pilot level discriminating circuit 28; and when the pilot signal exceeds a predetermined level, a region- classified signal pulse is applied to a class ''B: amplifier 29. The time constant of the load of the class ''B'' amplifier is set to a value longer than the period of the region-classified signal pulse. A switching circuit 23 is operated by the output of the amplifier 29 to operate a control circuit 24. |
