| 摘要 |
PURPOSE:To obtain a circuit which generates no erroneous alarm by monitoring by a monitor means, a difference voltage between a difference of two DC voltages when a phase shifter is in a phase reference state, and a difference of these two DC voltages when it is in a phase advance state, so that a phase-shifting quantity of the phase shifter is monitored. CONSTITUTION:Output voltages of detectors 23, 24 are denoted as VA and VB, respectively. The output voltage VA and VB are inputted to differential amplifiers 31, 32, respectively. The differential amplifier 31 outputs a voltage A1(VB- VA) proportional to VB-VA, and the differential amplifier 32 outputs a voltage A1(VA-VB) proportional to VA-VB. An output of the differential amplifier 31 in case when a 180 deg. phase shifter 10 is in a phase advance state is denoted as A1(VB-VA)1. When the 180 deg. phase shifter 10 is in a phase advance state, a differential amplifier 33 outputs a voltage A2{A1(VA-VB)0-A1(VB- VA)1} propor tional to a difference between A1(VB-VA)1 and the held A1(VA-VB)0. This output is compared with the upper limit VU and the lower limit VL of an allowable value by comparators 35, 36, and its output is inputted to a deciding circuit 19 and whether it is good or not is decided.
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