PURPOSE: To improve the reliability of switching from the active side by monitoring normality on the reserve side at all times by conducting the loop- back of a non-active side communication system at a counter line switching device and forming a loop.
CONSTITUTION: When a switching signal is '0', the communication with the opposite side is performed on the active side by connecting a first interface 101 to a third interface 103 and connecting a second interface 102 to a fourth interface 104. On the other hand, a sixth interface 106 is connected through a logic circuit 114 to a fifth interface 105, and the reserve side forms the loop with the counter station. When the switching signal is '1', the communication with the opposite station is conducted on the reserve side by connecting the first interface 101 to the fifth interface 105 and connecting the second interface 102 to the sixth interface 106. Then, the fourth interface 104 is connected through a logic circuit 113 to the third interface 103, and the active side forms the loop.
NAKAJIMA HIROHITO
ONUMA KAZUHIRO
OGAWA KAZUTADA
