| 摘要 |
PURPOSE:To expand the transmission range of information and to shorten a time related to the detection of a failure by sending a check signal to a closed loop constituted of continuous transmission control pairs adjacently arranged on the loop transmission line to detect abnormality and changing the number of transmission control pairs constituting the closed loop. CONSTITUTION:To detect the position of a failure, checking is started from a loop constituting a by-pass at a transmission control pair separated from the self-transmission control pair by kXn (k=1-n) sections on the loop transmission line and the check loop is narrowed successively from a far position to a near position. One cycle of a loop including a by-pass separated by n sections is checked at first, and if the checking is unsuccessful, the distance is successively narrowed like n-1, n-2-1. When a normal by-pass is not detected even if the sectional distance goes to ''1'', a by-pass is formed in the self-transmission control pair and the checking range is expanded from 2n to n+1 sections. When a normal by-pass is detected, the by-pass constituted in the self-transmission control pair is released and message transmission to the loop is restarted. |
