| 摘要 |
PURPOSE:To prevent system down when instructions are duplicated, by executing an instruction given afterward with priority, in a data highway which makes the loop back for the present and spare systems independently with the respective instructions from a monitor station. CONSTITUTION:When a present system loop back set instruction given from a monitor station 1 via a present communication line is applied to a set terminal (S) of an FF13 of a terminal station 2-2 and the present system loop back is made at the terminal station 2-2, a spare system loop back instruction is given to the terminal station 2-2 from the monitor station 1 via the spare transmission line and it is applied to a set terminal S of the FF14. It is set and this instruction is also applied to a NAND circuit 11, which has an output on the condition that no spare system loop back reset instruction is given from the monitor station 1. This output is applied to reset terminal R of the FF13, the present system loop back is released and the instruction coming later is executed with priority. |
