| 摘要 |
PURPOSE:To prevent the formation of a closed loop by releasing the loopback of its own repeater at the loopback command reception of other repeater. CONSTITUTION:In sending a loopback command having on identification number of a recovery repeater 1'-U from a terminal station (not shown) via a transmission line 2-U, a loopback command output 19-U of a command identification circuit 8-U and an output 20-U of a repeater number identification circuit 9-U go to H to set a FF 15-U thereby operating all optical shutter drive circuit 16-U. Then the optical signal branched by a branch circuit 6-U is reflected to an opposed repeater 1-D. In releasing the loopback 7, the output 19-U is brought into L by a release command. Moreover, in receiving the loopback command of the other repeater, the output 19-U goes to H and the output 20-U goes to L, then the AND gate 12-U goes to H to release the loopback. |
