| 摘要 |
PURPOSE:To exactly catch a start control signal of an emergency broadcast, by raising a detection sensitivity against a control signal within a prescrived frequency range. CONSTITUTION:When an emergency broadcast is started, its broadcast wave is caught by the antenna 1, and it is led out as an audible frequency signal through the high frequency circuit 2, the fixed contact 3a of switch 3, the intermediate frequency amplifying circuits 4, 5, and the detection circuit 6. A control signal is contained in this audible frequency signal, it is output by the filter 9, the relay 11 is operated by the output of the detection circuit 10, and the electric power source is supplied to the audible frequency amplifying circuit 7. When a broadcasting start control signal is detected by the detection circuit 10, in response to it, the switch 3 is switched from the fixed contact 3a side to the 3b side by the excitation signal from the delay switching circuit 13. Accordingly, as for the part of alarm contents following said broadcasting start control signal, its gain is lowered by the portion of the intermediate frequency amplifying circuit 4, by which broadcasting is sounded as an aural signal with good articulation. |
