Loop back control system in loop data transmission system

摘要

In a loop back control system of a loop data transmission system which has a transmission circuit consisting of duplex loop transmission lines, a plurality of remote stations connected to the lines, a master station for monitoring these remote stations, and a loop back function, loop back command data having a common address for the remote stations is set in a destination address field, and first and second parameter fields, in which the addresses of two remote stations subjected to loop back control are set, are sent from the master station to the plurality of remote stations through the lines. Each remote station receives the loop back command data and detects whether or not the self station address is specified. If the self station address is specified, loop back control switching is performed.