| 摘要 |
PURPOSE:To execute switching to loop-back without having a centralized control station, by switching a communication frame to a communication frame of the other system, executing the transmission to a communication line of the own system, and also inverting a logical value of an actual working/waiting informing signal in the communication frame, in case when a carrier of communication does not arrive from an upstream side, and an initializing frame arrives from the upstream side in the other system. CONSTITUTION:In case when a timer of a communicating station 11 becomes time-up first of all, transmission of a prescribed initializing communication frame is started from the communicating station 11, it is transmitted successively to a communicating station of the downstream through a commnication line 2, and the communicating station of the downstream executes the trigger of each timer. When both of the two systems are normal, the communication frame sent out from the communicating station 11 goes the round of each loop and is returned, therefore, when the communicating station 11 collates the returned communicating frame and confirms that there is no error, the system decided in advance becomes the actual working side and starts the regular communication. |
