| 摘要 |
PURPOSE:To prevent malfunction attended with the insertion of a pilot signal and the deterioration of a communication signal by rectifying an input/output signal of a communication transmission system respectively, converting the result into a DC voltage, supervising the ratio and applying switching when the ratio exceeds a prescribed range. CONSTITUTION:An input rectification circuit 4 rectifies an input signal of communication transmission systems 2, 3 being supervisory objects. Output rectifier circuits 5, 6 rectify an output signal of the communication transmission systems 2, 3. Divider circuits 7, 8 input a DC output voltage of the input rectifier circuit 4 and a DC output voltage of the output rectifier circuits 5, 6 and output an output signal Vc corresponding to the ratio of both inputs. A supervisory circuit 9 supervises whether or not the output value Vc of both the division circuits 7, 8 is within a prescribed range and use an output changeover circuit 1 to switch the communication transmission system when not within the prescribed range. That is, when the communication transmission system 2 or 3 is not operated normally, the ratio of the input/output voltage is not normal and the ratio of the DC output voltages exceeds a prescribed range. The supervisory circuit 9 supervises it, sends a switching signal to the output switching circuit 1, which applies changeover according to the signal.
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