| 摘要 |
PURPOSE:To obtain a circuit which can be easily set and is not disturbed by noise by providing an optical fiber cable between the transmitter and receiver sides of a fluid together with a light emitting element and a photodetecting element set at both sides of said cable and storing the middle part of the cable into a pipeline. CONSTITUTION:A part of an optical fiber cable 22 is stored into a pipeline 1 set between the feed and receiver sides of a fluid, e.g., between an outdoor gas meter 2 and an indoor gas tool 5. Both terminals of the cable 22 are drawn out of the line 1. An optical signal is supplied to a terminal 22a at one side from a light emitting element (not shown in the figure) which is set opposite to a gas alarm 6 and emits light when the leakage of gas is detected. While a terminal 22b at the other side applies an optical signal to a drive part 15 which is actuated by the output of a photodetector (not shown in the figure). With application of the optical signal, the part 15 closes a cut-off valve 3 to stop the supply of gas. This simplifies the setting of transmission lines and also prevents a malfunction due to a floating electric field. |
