FAULT DETECTION SYSTEM

PURPOSE:To decrease the intermission time of communication by detecting a faulty line control section by the control from a maintenance operating device in case of a fault giving disturbance onto a system bus of the line control section and switching the communication line to a standby line control section. CONSTITUTION:If a fault takes place in a system bus transfer control circuit 9-1, a maintenance operation control section 1 gives a command of disconnection from system buses 2, 3 to all line control sections 5-i and the line control sections 5-i are connected one by one sequentially to the system buses 2, 3 by the command from the maintenance operation control section 1 and the maintenance operation control section 1 confirms the communication to detect the line control section 5-i causing a disturbance to the system bus. Then a standby switching signal 30-i is sent to a standby changeover circuit 4 by a command of the maintenance operation control section 1 and the communication circuit 14-i accommodated in the line control section 5-i is switched to the line control section 5-i.