PURPOSE: To quickly cope with even the fault of a system far from a maintenance system and to improve the reliability of the system by automatically reporting fault information to the maintenance center.

CONSTITUTION: When the information of a serious fault is collected by a fault information control circuit 7, a central controller 8 instructs an ISDN terminal 2 through a maintenance device 9 to connect a line between the terminal and a maintenance center 12. The ISDN terminal 2 connects the line to transfer fault information from a central controller 8. When the information of a fatal fault leading to the system down is collected by the fault information control circuit 7, an automatic switching circuit 6 disconnects the ISDN terminal 2 from an ISDN line circuit 3 and directly connects it to a line terminating equipment 10. The ISDN terminal 2 connects the line between the terminal and the maintenance center 12 to transfer the fault information from the central controller 8.