Feeding system and feeding method for a submarine cable communication system

A feeding system for supplying a current to repeaters on a communication cable, said communication cable including a feed line for conducting a feed current to said repeaters, said feeding system comprising:

• branching units provided at branching points on said communication cable;
• and
• terminal stations each being connected through at least one of said repeaters to one of said branching units, and each of said terminal stations feeding said feed current through said feed line to said at least one of said repeaters,
• wherein each of said branching units having at least one switching circuit having a current threshold and connecting said at least one of said repeaters to one of said communication cable and ground, responsive to an amount of current conducting through said feed line in said communication cable, and the current threshold of each of the at least one switching circuit in said branching units being different from each other,
• wherein when a switching instruction, used for switching a feeding line provided in the submarine branching unit, is transmitted to said branching units, first currents having first values greater than the current threshold are sequentially supplied in a first order increasing in current magnitude form a first smaller current threshold to a first larger current threshold, and
• wherein when an instruction used for returning a feeding line provided in the submarine branching unit to the previous condition is transmitted to said branching units, second currents having second values greater than the current threshold are sequentially supplied in a second order decreasing in the current magnitude from a second larger current threshold to a second smaller current threshold.

A feeding method for supplying a current from terminal stations to repeaters, comprising the steps of:

• (a) connecting the repeaters to the terminal stations using a communication cable conducting current;
• (b) setting current thresholds in switching circuits different from each other;
• and
• (c) connecting a respective repeater to one of the communication cable and ground using a respective switching circuit responsive to the current conducted through the communication cable.