| 摘要 |
PURPOSE:To transmit the communication of >=1 pair for each set, by providing two pairs of transmission lines to transmit the digital signal to both forward and backward directions and having a connection with priority to the transmission line having a smaller number of terminal offices which are connected in a range from a transmitting terminal office through a receiving terminal office. CONSTITUTION:The communications of 3 pairs are transmitted among terminal offices A-B, C-D and E-F via two loop transmission lines with features that a loop R1 goes backward and rise and fall signals are always transmitted through a backward loop between terminal offices. In such a case, the communications of 1.5 pairs are transmitted for each loop. If the station E exists between stations C and D, the transmission is impossible between either one of E-F and C-D. However, an N-multiplexed digital signal transmission line is used in place of N pieces of loop transmission lines in a loop transmission system, and >=10 systems are usually used for both the value of N and the number of terminal offices. Then an idle loop is looked for, and the rise and fall signals are connected in a backward loop and between the side close to the loops at all times. Thus the effective transmission is ensured on an average. |
