PURPOSE: To make it possible to dispersedly arrange a line IF in the distance and to increase line/trunk circuit regardless of the line IF within a main body by performing a packet transmission from a central control part by defining a card address given to the interface (IF) card of each line as a destination address.

CONSTITUTION: A CPU 60-2 discriminates the card address allocated to a L/T system card 72 at a remote place by referring to the address field of a control packet and transmits the address to a communication path 60-5 through a SIO 60-3 via a bus 60-4. At this time, the CPU 60-2 recognizes the storage position of a RUT-60 by referring to an I/O port, sets a new address value which an offset value from the head of a line/trunk part 30 is subtracted from the address value of the control packet to the packet and transmits the new value to the communication path 60-5. The control packet is transmitted to a transmission line 80 by being multiplexed. The packet enters a multiplexing switch 73-6, and then it is restored to its original control packet and transmitted to a control highway 714 in a direction of a RU 70 via a M-ILSI73-1.