| 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. <H0> ABSTRACT </H0> An input signal discrimination method is provided wherein the on/off state of an AC input signal is discriminated. An AC input signal (1) is input to a processor (21) through a photocoupler (13). The processor (21) counts pulses in a time for which the AC input signal (1) remains above a predetermined threshold level, and a time for which the signal remains below the predetermined threshold level. When the number of pulses counted while the signal remains above the predetermined threshold level is larger than a previously calculated number, it is decided that the AC input signal is on, and when the number of pulses counted while the signal remains below the predetermined threshold level is larger than a previously calculated value, it is decided that the AC input signal is off. Consequently, the on/off state of the AC input signal can be accurately discriminated in a short period of time.</p> |
