| 摘要 |
PURPOSE:To attain a flexible system that excels in a physical effect and furthermore and cope easily with the system change, by defining the fail-safe output as one of features with a single trouble occurring at a signal output end when a digitized product is applied. CONSTITUTION:The signals sent to drivers I and II of an output PI are delivers to photocouplers I and II to be turned into redundant signals. These signals are sent to an equipment set at a job site and then supplied to an AND circuit and an OR circuit by a changeover switch for AND and OR connection. Thus the fail-safe side can be turned ON or OFF for each signal. When the changeover switch is set at the side (a), for example, both transistors I and II secure AND connection. Then OR connection is secured when the switch is set at the side (b). In other words, both transistors work at the OFF signal side and never deliver ON signals at worst. |
