| 摘要 |
PURPOSE:To obtain an inexpensive switching control circuit for the breaking of a transmission line by providing a change-over circuit at the terminal point of the transmission line and by supervising and changing over the transmission line at the terminal point. CONSTITUTION:Central controller 1 is connected to terminals 2-1-2-N and change- over device 8 via transmission line 3 and reception line 4 and provides transmission and reception of information signals in the known method. On the basis of received signals from reception signal 4, central controller 1 exercises a supervision over abnormality of reception signal 4 and change-over device 8 supervises abnormality of transmission line 3 on the basis of signals from transmission line 3. If abnormality is detected on transmission line 3 or reception line 4, central controller 1 and change- over device 8 cooperate with each other to make connections between stand-by transmission line 9 and transmission line 3, and stand-by reception line 10 and reception line 4 in change-over device 8, thereby evading the abnormality. |
