| 摘要 |
PURPOSE:To inform quickly the search for a faulty station even in a double fault mode among plural slave stations by replacing the data received by a signal line with the reception data to be sent to a loop-back line by a slave station which received a loop-back command from a master station. CONSTITUTION:A master station #1 and slave stations #2-#n are connected in a loop from to a transmission line containing a signal line l1 and a loop-back line l2 through which signals are sent in the different directions. Then data are transmitted among these master and slave stations. The station #1 transmits the same signal to both lines l1 and l2. When a loop synchronizing control part 7 of the station #1 detects a fault of the line l1, the address of a slave station to be looped back is transmitted together with a loop-back command signal. A loop- back control part 5 of a slave station which received said command signal converts the signal sent from the line l2 into a digital signal by a signal converter 4 in place of the signal sent from the line l1. This digital signal is sent to the line l1 via a signal converter 3 in the form of the reception data. Then a data highway loop is formed. The loop-back command is sent successively to slave stations to secure a quick search for a fault even in a double fault mode. |
