| 摘要 |
<p>PURPOSE:To detect the absence of an input signal at a high speed with high reliability by providing a circuit which holds a signal-absence output state starting from the 1st decision circuit decides on that the signal is absence until the 2nd decision circuit decision on that signal is absence. CONSTITUTION:The 1st deciding circuit 14 which decides on whether an input signal is present or not based on the signal level is high or low and the 2nd deciding circuit 5 which makes a decision on whether an input is present based on the frequency characteristic of the signal, individually. The holding circuit 6 holds the output state of signal absence from when the 1st deciding circuit 4 decides on signal absence at least until when the 2nd deciding circuit 4 makes a decision, and the AND signal between the outputs of the 2nd deciding circuit and holding circuit 6 is outputted. Thus, the signal absence is detected at a high speed, the influence of noise is eliminated, and the reliability is improved.</p> |
