| 摘要 |
PURPOSE:To improve a receiving characteristic and to attain a low noise reception by outputting the prescribed detection output signal corresponding to the intensity of a reception electric field and outputting a detection signal from the 2nd detection circuit if the level of the noise of a multibus exceeds the prescribed level. CONSTITUTION:If the level of the multibus noise exceeds the prescribed lst threshold level SL1, a switching circuit 53 switches to another reception antenna 52 with different directivity. Simultaneously a noise level discrimination part 60 supervises that the level of the multibus noise continuously exceeds the 2nd threshold level SL2(>SL1) more than the prescribed time TR. If so, the part 60 outputs a switching control signal SD at a high level to a switching circuit 62 regardless of the level EA of a level meter output, and further outputs a detection signal DMR from a ratio detection circuit 53 to a noise killer 63 by means of the switching circuit regardless of the level of the reception electric field. After the prescribed time TC is elapsed since the level of the multibus is below the 2nd threshold level SL2, a detection signal is selectively outputted based on the output of a level meter.
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