| 摘要 |
PURPOSE:To miniaturize the equipment and attain high reliability by providing a drop-out detecting means that detects no signal state, an integrating means and a specific logic circuit means and thereby constituting the detecting circuit for presence or absence of signal of a digital circuit. CONSTITUTION:The circuit is provided with a drop-out detecting means 11 that detects no signal state, an integrating means 13 that makes output of the drop-out detecting means 11 input, and a logic circuit means 14 that makes output of the integrating means and output of the drop-out detecting means 11 input, and output is inverted by inversion of output of the integrating means 13 when the no signal state is detected and output is inverted by inversion of the drop-out detecting means 11 when a signal is detected. A comparator etc., is used for the drop-out detecting means 11, a counter etc., is used for the integrating means 13, and an AND circuit and an OR circuit are used for the logical circuit means 14. By this constitution, whole of the detecting circuit for presence or absence of signal can be digitalized, the equipment is miniaturized, and reliability is improved.
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