| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately grasp whether an optical terminal device gets out of order at a center device side by a simple constitution. <P>SOLUTION: A center device 2 and the optical terminal device 4 are connected to each other through an optical transmission line 6. The optical terminal device 4 includes a video optical terminal 4a and a communication optical terminal 4b. The center device 2 transmits an optical television signal and an optical control signal to the video optical terminal 4a through the optical transmission line 6 to optically communicate with the communication optical terminal 4b through the optical transmission line 6. The video optical terminal 4a converts the optical television signal and the optical control signal into an electric television signal and an electric control signal by a photodiode 10. Amplification stages 18 and 20 of amplifying and outputting the electric television signal to the outside of the video optical terminal are turned on and off according to the electric control signal. Output levels of the amplification stages 18 and 20 are detected by detection circuits 38 and 40 and compared by a microcomputer 32 with thresholds, and comparison results are transmitted to the center device 2 through the communication optical terminal 4b. <P>COPYRIGHT: (C)2010,JPO&INPIT |
