| 摘要 |
PROBLEM TO BE SOLVED: To prevent a squelch circuit from malfunctioning even if received electric field strength is low. SOLUTION: A reception means 2 receives a radio signal including a tone signal. When a tone signal is included in the output signal of the reception means 2, a tone detection circuit 10 detects it. When the tone detection circuit 10 detects the tone signal, an opening/closing switch 8 is closed. When the tone detection circuit 10 does not detect the tone signal, the opening/closing switch 8 is opened. When the reception electric field strength in the reception means 2 is small, a control section 22 sets the tone detection circuit 10 to the non-detection state of tone signals.
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