| 摘要 |
If the fibre line is destroyed in an optical transmission path, laser light emerging from the fibre ends at the break point may endanger people. The intermediate regenerators of the optical transmission path are fitted with signal detectors and switching means, and the line terminal devices are fitted in addition with logic circuits, time circuits and signal generators. The afore-mentioned units interact in such a way that all optical transmitters which transmit into the defective field are automatically de-activated. Once the transmitters have been de-activated, the optical path remains in a condition which allows the defective field to be located from the line terminal devices. The optical transmission path is returned to service after repair from the line terminal devices.
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