| 摘要 |
PURPOSE:To ensure the squelch control even when an interference wave is received by using a detection output attended with a change in an electric field and a monitor voltage with noise rejected so as to apply the squelch control. CONSTITUTION:When a received electric field monitor voltage is changed suddenly, a differentiation change corresponding to the change appears in a differentiation circuit 2 as shown in a waveform (c), and when its output is higher than a threshold voltage of a comparator 3 and a set signal of a FF 5 is outputted from the comparator 3 as shown in a waveform (d). When a voltage with noise rejected by a low pass filter 10 from the received electric field monitor voltage is higher than a threshold voltage of a comparator 4 as shown in a waveform (b), a reset signal of the FF 5 is outputted from the comparator 4 as shown in a waveform (e). Since the squelch control signal from the FF 5 is controlled by the set signal of the comaprator 3 and the reset signal of the comaprator 4 in this way, the sure squelch control is applied.
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