| 摘要 |
PURPOSE:To always monitor lines of 0 and 1 systems by utilizing a data signal of an active system even when phases of a 0 system signal and a 1 system signal are coincident with or different from each other. CONSTITUTION:In order to monitor and switch a 0 system signal 5101 and a 1 system signal S102, a monitor pattern signal P is detected independently by any of detection circuits (A) 21, (B) 22, (C) 23 from outputs of respective selection circuits (A) 11, (B) 12, (C) 13 through the selection circuits (A) 11, (B) 12, (C) 13 and the changeover is implemented periodically. When the phases of the 0 system signal and the 1 system signal are coincident with or different from each other, a data signal of the active system is utilized and the line of the 0 and 1 systems is always monitored. |
