| 摘要 |
PURPOSE:To perform effective backup operation by performing automatic switching to a receivable route for communication if one route is cut off or in case of such abnormality that either slave station loses its repeating function. CONSTITUTION:When slave stations 2 and 3 are unable to receive call signals even after the elapsed time of polling through an A route 6, a time monitoring circuit 28 sends a signal to inverts the contents of a route selection memory 29, and a selector 25 receives the call signal from a B route 7. A master station 1, on the other hand, is able to receive answer signals from the slave stations 2 and 3 from the A route 6 and an answer station from a slave station 5 from the B route 7, so the time monitoring circuit does not receive the signal even the specific elapsed time later so far as the other route is selected. In this case, the contents of the selection memory are rewritten into the A route 6 for the slave stations 2 and 3 and the B route 7 for the slave station 5 to perform automatic recovery, so that there is no hindrance to communication. |
