| 摘要 |
PURPOSE:To prolong the service life of a light emitting element by intermitting the lighting of the light emitting element at a light source section. CONSTITUTION:An electronic switch SW switched at high speed is provided in series with a circuit of a light emitting element 4 of a light source section 1-1 and a light signal (a) obtained by interrupting the lighting of the element 4 through the interruption of a current flowing to the element 4 is inputted to a sensor 2 via an optical fiber 5. When an AC voltage (b) is fed to an electric input section of the sensor 2, the intermittend light power (c) corresponding to the inputted voltage (b) from an output of the sensor 2 is inputted to a photoelectric converting section 3 via an optical fiber 6 and an intermittent voltage (d) corresponding to the voltage (b) inputted to the sensor 2 is outputted. The voltage (d) is inputted to a filter 7, a high frequency component is eliminated, a voltage (e) corresponding to the voltage (b) is outputted and given to e.g., a fault locator. Since the lighting of a light emitting element 4 is intermitted, the lighting time per unit time is decreased and the service life of the element 4 is prolonged. |
