LOOP-SHAPED TRANSMISSION SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a loop-shaped transmission system capable of detecting the disconnection of a transmission line at one spot and identifying the abnormality of disconnecting the transmission line more than two spots and abnormality at a slave station or pull-in part thereof. SOLUTION: This system is provided with a switching device 16 for connecting a transmission/reception part 14 of a master station and respective divided transmission lines and switching the state of connecting the transmission/reception part and the divided transmission line through two relay contacts 17 and 18 capable of dividing and respectively independently operating a transmission line 10 to connect the master station while defining at least one unit 1 of transmission control units 1-n as a master station and the other units as slave stations when many transmission control units 1-n capable of mutual transmission/reception are successively connected in the shape of loop by the transmission line 10 and a control means 11 for controlling the ON/OFF state of the relay contacts constituting the switching device 16 and for detecting at least one of the disconnecting spot of the transmission line, the fault of the slave station and the disconnection of the pull-in transmission line thereof based on that ON/OFF state and the presence/absence of a response to the transmission from the master station from the slave station.