PURPOSE: To manage existing terminal equipment centralizingly by accommodating plural existing terminal line adaptors and using a call control function of a broad band line adaptor section to process an interface control signal including call control information from the adaptor.

CONSTITUTION: Existing terminal interface signals R1-Rn are subject to termination processing by existing terminal termination sections 31-3n of existing terminal line adaptors 50-5n, its output information is converted into an ATM cell by a cell composition section of ATM cell composition and decomposition sections 21-2n for user information and outputted to a cell multiplexer section of an ATM cell multiplex/demultiplex section 12 of a broad band line adaptor section 40, the cell multiplexer section integrates plural ATM cells into one cell and it is outputted to a next stage broad band line termination section 11. The termination section 11 converts the ATM cell into an STM-1 frame of a broad band line interface signal UN1 and sends the signal to the network.