IMPROVEMENTS IN OR RELATING TO POWER SWITCHING OF OPTICAL FIBRE CABLE BRANCHING UNITS

摘要

A branching unit for an optical fibre cable system of the type which has an electrical power conductor for feeding current to electrical equipment provided along a main cable and a communication system and method of operating such a system. The branching unit (10) has first and second connections (12, 14) for coupling two sections of trunk cable (16, 18) and a third connection (24) for an optical fibre spur cable (26). A switch arrangement (RL1, RL2, D9, D10) is provided which is responsive to a control voltage provided on the conductor of the spur cable (26) to apply an earth (36) to the conductor of the trunk cable (16, 18). This maintains a current path in one trunk section when a failure or break occurs in the other trunk section.