| 摘要 |
PURPOSE:To eliminate the influence of a noise such as a disturbing radio wave while maintaining high insulation by utilizing light for power transmission to a primary circuit, and also using the output light of the primary circuit for power transmission to a secondary circuit. CONSTITUTION:Light of frequency f0 from a light emitting device 16 is passed through an optical transmission line 22 to illuminate a photoelectric converting element 7, generating electromotive force of frequency f0. While a pantograph 1 and a primary detecting circuit A are both normal, light emitting elements 3 and 4 emit light at frequency f0, and the light of frequency f0 strike photodetecting elements 12 and 13 to energize relays 14 and 15. Optical amplifiers 10 and 11 are narrow-band selective amplifiers with a center frequency f0. If, however, the pantograph 1 is broken and a detection line 2 is cut off, neither the light emitting element 2 nor the photodetecting element 12 operates and the relay 14 is unenergized to close a breakage detecting circuit 23, indicating the breakdown. The failure of an optical transmission line 20 is the same. If one of the light emitting device 16, optical transmission lines 21 and 22, light emitting element, a resistance 6, the photoelectric converting element 7, and the optical amplifier 11 breaks down, the relay 15 is unenerigized and the defect detecting circuit 24 indicates the defect. |
