| 摘要 |
PURPOSE:To remove a restriction on the fault supervisory section length of an interposing line by sending a fault supervisory signal to a light transmission line without using any interposing line. CONSTITUTION:The photoelectric conversion output of input circhit 2 connecting with optical fiber 1 is equalized and amplified 3, and discriminating-reproducing sircuit 4 discriminates and reproduces a digital signal, which is electrophoto-converted by output sircuit 5 by way of switching circuit 19 before being sent to optical fiber 20. Part of the output of circuit 2 is input to level supervising circuit 16 and remote command discriminating circuit 17 to decide on the lowering of the input level and on an operation stop signal sent out from a transmitting station. On receiving a clock signal from voltage control oscillator 13, fixed pattern generating circuit 18 generates a string of pulses of a pattern assigned to each repeater. Circuit 16, when circuit 17 generates an output, puts circuit 18 into operation to control circuit 19, thereby sending a string of fixed pulses. Consequently, the orientation of a fault point comes into effect without using any interposing line, so that the long- distance repetition of the digital signal can be attained by the optical fiber. |
