| 摘要 |
PURPOSE:To obtain an economical transmission line of high quality by transmitting a signal for the gain control of the main transmission circuit of an intermidiate repeater installed on a communication line by using the only the main transmission line, in an automatic gain controller. CONSTITUTION:In intermediate repeater 4, a communication signal has its line loss compensated by amplifying board 5. Variation in signal level is detected by control board 6 of receiving terminal station 2 and when the detection value exceeds a criterion, a control signal is sent out by using a low-frequency signal outside of a communication signal band. This control signal is separated from the communication signal by power separating filter board 8, inputted to control board 7, and detected, thereby controlling the gain of amplifier 5. The control signal branched by board 8 is transmitted through a low-pass circuit and supplied to main transmission line 3 by way of power separating filter board 9. The low-pass circuit is so constituted that signals will bypass amplifier 5 and will never be disturbed by directional amplifier 5. |
