| 摘要 |
PURPOSE:To simplify devices and to check a fault in an in-use station and a backup station at the time of switching by receiving a data signal from a slave station by the backup station during the communication with the in-use station and making an operation controlling part control the switching. CONSTITUTION:If a receiving signal is not detected by one of an in-use station 22 and a backup station 22', the operation controlling part 33 sets up the by-pass mode in the station 22', a circuit is passed through a by-pass line 40' and the station 22 sends a check code to the circuit. When the code is received by the station 22 through the slave station 21 and the by-pass line 40', the fault of a transmitting/receiving part of the station 22' is diagnosed and communication between the station 22 and the slave station 21 is restarted. When the check code is not received by the station 22 within a fixed period, the station 22 is decided to be defective and the control part 33 sets the station 22 to the connection mode, switches the station 22' to the connection and transmission modes and sends the check code to the circuit. When the code is received by the station 22', it is confirmed that the station 22 is defective and the station 22' starts to communicate with the slave station 21. The station 22' can check the faults of both the stations at the time of switching without the collection of past data. |
