| 摘要 |
PURPOSE:To stabilize the switching action between using and spare loops, by using a control loop which is separately prepared. CONSTITUTION:In order to know the state of the loop connection, a switch SW3 of a control loop L3 is switched to a state shown by dotted lines from a state shown by 1-dot chain lines and a general loop controller 13 is connected to the loop L3. A control signal shown in the figure (a) is transmitted to a control circuit 16 of the loop L3 from a monitor device 11 via the loop L3. This control signal recognizes that the using loop is equal to a loop 1 and the working mode of the using loop is N meaning the normal state. At the same time, a node part 10-0 feeds a constitution request to the device 11. Then a changeover switch SW2 is changed to an ON state shown by the dotted lines in order to have a connection to a spare loop L 2. As a result, the controller 13 is connected to the loop L2, and the signal of the loop L2 is transmitted to a control circuit 15 of the loop L2 via a receiver R2. |
