| 摘要 |
PURPOSE:To check abnormalities in a titled optical signal transmitting system by monitoring the intervals of low levels in receiving signals at the receiver side, by monitoring an information signal at the transmitter side, by making a pulse signal when there is no information signal for a fixed period, and by optically transmitting the pulse signal. CONSTITUTION:A fixed time is set to a pulse adding circuit 11 of a transmitter 1, the adder 11 outputs a pulse at a fixed time interval during a period where an information signal outputted from a sensor 10 is in a range from the trailing edge to a low level, and the pulse is added to the information signal digitally. This added signal is converted into an optical signal at an electrooptic converter 12, and made incident to a receiver 3 through a light transmitting path 2. This optical signal is converted into an electric pulse at a photoelectric converter 13 and the pulse is discriminated through a low-pass filter 14. An abnormality detecting circuit 15 monitors the interval of signals at low level. In this way, abnormalities in the light transmitting path 2 and the transmitter 1 are detected. |
