| 摘要 |
PURPOSE:To accomplish protection of contact points and noise suppression with low cost by providing a D-type flip-flop whose clock input is an output from a window comparator and D-input is a signal to drive a relay, and a relay driver to drive the relay by means of an output signal from the flip-flop. CONSTITUTION:By setting the values of two threshold voltage to vicinity of zero volt, a pulse which shows a time when the input voltage of the window comparator 15 becomes approximately zero i.e. the call-signal current is approximately zero is obtained. Because the output of the comparator 15 is connected to the clock input of the D-type flip-flop 11, even when a drive signal turns from 'H' to 'L' and a restoration of relay is commanded, the said flip-flop does not immediately inverses its output. Instead, only when a pulse that shows that the input voltage crossed a point close to zero is outputted by the comparator 15, the flip-flop turns its output to 'L', and the relay is restored at this point of time.
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