| 摘要 |
PCT No. PCT/GB97/00567 Sec. 371 Date Oct. 31, 1997 Sec. 102(e) Date Oct. 31, 1997 PCT Filed Feb. 28, 1997 PCT Pub. No. WO97/32409 PCT Pub. Date Sep. 4, 1997A branching unit for an optical fiber transmission system has a pair of inputs/outputs for receiving an end of a different section of trunk cable of the type having an electrical conductor and one or more pairs of optical fibres. A switching circuit (8) is effective to selectively route power between the electrical conductors (54, 56) of each trunk section or via an earth return (72) in response to a supervisory signal provided on the trunk. |
