| 摘要 |
PURPOSE:To prevent the interrupting operation of a DK signal from responding to in a way of chattering by providing a means increasing the detection sensitivity of an SK signal at detection and decreasing it at non-detection. CONSTITUTION:When an antenna input is decreased and reaches a sensitivity level C or below decided by a resistor R3, even when the SK signal exists,it is not detected and the level of an SK indicator terminal 3 goes to H level, then an SK indicator goes off, a signal output from a DK output terminal 4 is stopped, and the setting sensitivity of a sensitivity setting terminal 5 is switched from the sensitivity decided by a resistor R3 into the sensitivity decided by a resistor R3+R4, resulting that the sensitivity is lowered. Since there is a hysteresis between the antenna input level when the SK indicator terminal 3 is from H into L and the antenna input level switched from L into H, no chattering takes place in the detecting operation of the SK signal, resulting that no chattering takes place even in the interruption of the DK signal.
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