NETWORK CONTROLLER

PROBLEM TO BE SOLVED: To simplify the configuration and to reduce the cost by controlling the operating state of a primary impedance changeover circuit, a DC consumption changeover circuit and a secondary impedance changeover circuit with less number of control signals than that of a conventional network controller. SOLUTION: A secondary impedance changeover circuit 8 validates any of impedance adjustment circuits 8a, 8b, 8c, 8d depending on a state of control signals S1, S2 given to an analog switch 8e. A relay 4c of a primary impedance changeover circuit 4 validates either of impedance adjustment circuits 4a, 4b under the control in response to a state of the control signals S1, S2 through a NAND gate 22 and a driver 11. Photocouplers 6d, 6e of a DC consumption changeover circuit 6 validate either of DC consumption circuits 6a, 6b under the control of a state of the control signal S1, S2 through an AND gate 23 and drivers 12, 21.