Abstract: The remote monitoring system locates individually the pairs of intermediate amplification circuits in a remote location in the transmission line between a monitoring station and a monitored station in which circuit a fault diminishing amplification is to be located. The monitoring station transmits remote location signals and other control signals which can be mixed with the data signals normally transmitted over the line. The monitoring station analyzes any faults in the signals transmitted and looped in the line and also carries out remote-control of the gain variation of each amplification circuit without normal transmission of the data signals being interrupted. Signals transmitted from by the monitoring station over the forward channel of the line control four loops of the inputs and outputs of a remote located pair of amplification circuits and a gain regulating means inserted in the negative feedback loop, or inserted upstream or downstream of each amplification circuit in order to change its gain.