| 摘要 |
PURPOSE:To obtain an economical signal supervising circuit by supervising an output of a detecting circuit detecting the stop of an optional signal among plural signals and generating a fault alarm by an output of a detector detecting the stop of output of other signals. CONSTITUTION:A signal tone applied to a signal tone supervising input terminal 1 is amplified and rectified to turn on a transistor (TR) 20. When an intermitting earth signal int is at a ground level, an MR relay 21 of a load of the TR20 is turned on only for a time when a capacitor C22 is charged, a contact mr23 restores a time limit circuit and keeps a TR24 off, then an AL relay 25 is not operated. When a signal tone is interrupted by a fault, the TR20 is turned off and the relay 21 is kept restored and when time reaches a set time limit of a time limit circuit, the TR24 is turned on, the relay 25 is operated, a contact al26 is closed to alert an alarm. Even if the signal tone is normal, when the signal int is stopped while the line is kept opened or grounded, the relay 21 is not operated, only the TR24 is turned on and alarm is alerted by the relay 25. |
