| 摘要 |
PURPOSE:To attain the accurate detection of drop-out by detecting the drop-out of a frequency modulation signal in accordance with the output signal of a latch means. CONSTITUTION:If the instantaneous frequency if the frequency modulation signal (a) deviates from a regular frequency range and falls below a minimum frequency, the terminal voltage (c) of the capacitor 103 at a moment when a switch 102 closes falls below a second reference voltage Vr, whereby the output signal (d) of a comparator 105 shows 'H'. A latch 107 latches it, and holds it until the rise edge of the output signal (b) of a next limitter 108 comes. If the instantaneous frequency of the frequency modulation signal (a) falls below the minimum frequency for several periods, the output (e) of the latch 107 continuously shows 'H'. The output (e) of the latch 107 shows 'H' if the frequency modulation signal (a) is deviated to the side of a low frequency, whereby the detection of drop-out can be executed.
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