BRANCHING UNIT FOR AN OPTICAL FIBRE TRANSMISSION SYSTEM

摘要

A branching unit for an optical fibre 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.