PURPOSE: To reduce the number of the necessary line by installing the 3-winding transformer to both the transmitter side and the receiver side each.

CONSTITUTION: The signal of main track 2 is transmitted to the line from transmission amplifier 6 after piling of the feed current and then transmitted to the terminal via repeater 1. At the same time, the feed current is isolated from the signal through the final repeater and then fed back to phantom feed unit 3 from the intermediate tap of 3 wiring transformer 10 via the intermediate tap of 3-winding transformer 11 and through feed flyback line 4. While the repeater monitor signal is inserted from trak 2 to be delivered to terminal 7 via folded circuit 8 and feedback line 4. And the previous arrangement between the transmitter and receiver sides is carried out via line 4 and by connecting the order-wire equipment to terminal 9 and 12.