| 摘要 |
The present invention increases reliability of a monitor of a normally closed contact point in a relay unit. In a de-energized state, the relay unit transmits a diagnosis signal to normally closed contact points (b1,b2), performs detection of a return situation of the transmitted diagnosis signal; retransmits the diagnosis signal when the result of the detection cannot satisfy a certain condition, performs re-detection of the return situation of the retransmitted diagnosis signal, and determines the diagnosis signal as a normal state when the result of the re-detection satisfies a predetermined condition. |
