| 摘要 |
PURPOSE:To make the line in duplicate with an opposite terminal station only by dividing a transmission signal into n:1, sending the result to an active line 1 and a standby line 2 respectively, allowing a reception section to add both signals, adjusting the level automatically and outputting the result. CONSTITUTION:Photocouplers 241, 242 distribute an optical output of optical transmission sections 221, 222 into n:1 (n<1) and send them to an active line 26 and a standby line 27. Moreover, photocouplers 251, 252 superimpose an optical signal of the active line 26 and an optical signal of the standby line 27 and input the result to optical reception sections 231, 232. An optical/electric conversion circuit (O/E) 31 of the optical reception section converts an input optical signal into an electric signal, an automatic gain adjustment (AGC) circuit 32 applies automatic gain control to the electric signal input from the O/E 31 to generate an output. An identification circuit 33 identifies an output signal from the circuit 32 and generates an output. Since the signal level of the active line is larger than the signal level of the standby line by a multiple of (n), the signal of the active line is identified independently of the signal of the standby line by selecting a threshold level for identification in the circuit 33 to be a value between the signal level of the active line and the signal level of the standby line. |
