| 摘要 |
PURPOSE:To prevent production of a code error at automatic changeover by ORing a control circuit output and a standby optical transmission circuit control output as an operation stop signal of an active optical transmission circuit and switching the circuits after a standby optical transmission circuit is active. CONSTITUTION:After the standby optical transmission circuit 3 is started, when a switching control signal (g) is brought into an L level after a time T1 elapses while the circuit is active, the standby optical transmission circuit 3 is switched from the nonoperating state into the operating and an optical output (d) is generated. On the other hand, a switching control signal (h) is already logical L and since an output operation stop signal (i) of the OR circuit 6 goes from H to L by the L level of the switching control signal (g), the active optical transmission circuit 2 is inactive and the optical output (c) is lost. Thus, since the switching is applied while the active optical transmission circuit 2 and the standby optical transmission circuit 3 are both active, an output signal (j) is sent to the optical repeater of the next stage without mistaking the code at automatic changeover. |
