| 摘要 |
PURPOSE:To improve reliability without switching circuits in case of a fault of a transmission line by composing a loop transmitting circuit of a couple of transmission lines and performing polling transmission so that when information is received from one transmission line, information arriving from the other transmission line is not received. CONSTITUTION:A center transmitter CT and plural terminal transmitters T1, T2-Tn are looped in series by couples of transmission lines L1, L2-Ln, and Ln+1. This transmitter CT sends polling information for calling the terminal transmitter T1 or a control signal with a polling function to the transmission lines L1 and Ln+1 on both ends at the same time. The respective transmitters T1, T2-Tn receiving the information receive information from one transmission line to relay it to the other transmission line, and also input display information I1 when the polling information is received to send the information I1 to respective transmission lines L1, L2-Ln, and Ln+1, receiving information from none of other transmission lines. Then, switching is not performed in the event of a fault among the transmission lines L1, L2-Ln, and Ln+1. |
