| 摘要 |
<p>A circuit which gives a continuous voltage output indication of whether a contact is open or closed. The circuit senses the voltage across the contact to detect whether the contact is open or closed. When there is a significant voltage, the circuit indicates that the contact is open. When the voltage is negligible, the circuit indicates that the contact is closed. Alternatively, the current through the contact can be sensed to provide an indication of whether the contact is conducting or not. The circuit can be used to indicate welding closed of a relay contact in which case power to the load can be turned off or the contact can be opened by other than normal means. One application is to discontinue closing movement of a garage door when the motor relay switch does not open as desired, but there are innumerable other applications.</p> |
