| 摘要 |
PURPOSE:To enable to ensure to separate the terminal station in relation to the production of a failure easily, by transmitting the output of time-up of a timer to a photoswitch and separating the terminal station from the phototransmission line, when the loop shape transmission line is not normal. CONSTITUTION:If a failure of transmission is produced at the terminal station of the preceding position immediately before, or a reception failure is produced at the main terminal station, when a failure detection circuit 23 detects the absence of a reception signal (a) for a given time or more, the switching state of a selector switch 24 is controlled with a switching instruction (d). That is, if the loop shape transmission line is not normal, the identifying signal (e) specific to the terminal station is transmitted to a master station via a selector switch 24, phototransmitter 14, and post terminal station, and a timer 25 is started with the instruction (f). Further, the output (g) after time-up of the timer 25 is given to a photoswitch 7 via an OR gate 28, and the terminal station is separated from phototransmission lines 6 and 8. Thus, the terminal station relating to the production of failure can easily and surely be separated. |
