| 摘要 |
<p>An input signal determination system for determining whether the state of an ac input signal is on or off. An ac input signal (1) is input to a processor (21) via a photocoupler (13). The processor (21) counts the time in which the ac input signal (1) remains higher than a predetermined threshold level and the time in which it remains lower than the predetermined threshold level. When the counted number for the higher level is greater than a precalculated number, the ac input signal is determined to be on, and when the counted number for the lower level is greater than the precalculated number, the ac input signal (1) is determined to be off. This makes it possible to correctly determine the on/off state of ac input signals within short periods of time.</p> |
