| 摘要 |
PURPOSE:To easily detect a position where a line is disconnected by providing supervisory signal generation parts in respective work stations (WS) in a data communication system. CONSTITUTION:The transmitted data of the WS #1 is transmitted to the WS #2 through a transmission control part 1 and a signal for monitoring the line between the WS #1 and the WS #2 is generated in the supervisory signal generation part 2 and transmitted to the WS #2 via an OR gate 3 and a transmitter 4. In the WS #2 the data from the WS #1 or the supervisory signal is received by a receiver 5 and the data and the supervisory signal are identified in a discrimination part 6. When the received signal is the data, the data is transmitted to the next WS through a communication line 21 via a reception control part 7, a process part 9 and a transmission control part 10 to form a loop system. Meanwhile if the received signal is the supervisory signal, the supervisory signal is transmitted to a line supervisory part 8, where the period of the supervisory signal or the existence of the supervisory signals is detected and if the abnormality of the line such as disconnection, etc., is detected the abnormality is informed to the process part 9.
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