A communications system including a first receiver unit connectable with a transmission channel and configured to determine a signal power of a first communications signal received over the transmission channel and comprising a noise detection unit configured to measure noise above a predefined noise level in the communications signal during reception of the communications signal, a first transmitter unit connectable with the transmission channel and configured to transmit the first or a second communications signal, wherein a gain of the communications signal which is output by the first transmitter unit is controllable, a second transmitter unit configured to transmit a gain control signal over the transmission channel, and a first control unit configured to control the gain of the first transmitter unit in response to the gain control signal such that the signal power is high enough to ensure safe reception of the communications signal and low enough to facilitate, during reception of the first communications signal, a measurement of noise of the predefined noise level; wherein the first receiver unit is integrated in a second modem device, the second modem device further comprising the second transmitter unit, and a second controller unit connected with the first receiver unit and the second transmitter unit and configured to initiate transmission of the gain control signal, when the determined signal power exceeds a first predetermined threshold level; and the first transmitter unit and the first control unit are integrated in a first modem device, the first modern device including a second receiver unit connected with the transmission channel and configured to receive the gain control signal, wherein the first transmitter unit is configured to transmit the first communications signal. a first receiver unit connectable with a transmission channel and configured to determine a signal power of a first communications signal received over the transmission channel and comprising a noise detection unit configured to measure noise above a predefined noise level in the communications signal during reception of the communications signal, a first transmitter unit connectable with the transmission channel and configured to transmit the first or a second communications signal, wherein a gain of the communications signal which is output by the first transmitter unit is controllable, a second transmitter unit configured to transmit a gain control signal over the transmission channel, and a first control unit configured to control the gain of the first transmitter unit in response to the gain control signal such that the signal power is high enough to ensure safe reception of the communications signal and low enough to facilitate, during reception of the first communications signal, a measurement of noise of the predefined noise level; wherein the first receiver unit is integrated in a second modem device, the second modem device further comprising the second transmitter unit, and a second controller unit connected with the first receiver unit and the second transmitter unit and configured to initiate transmission of the gain control signal, when the determined signal power exceeds a first predetermined threshold level; and the first transmitter unit and the first control unit are integrated in a first modem device, the first modern device including a second receiver unit connected with the transmission channel and configured to receive the gain control signal, wherein the first transmitter unit is configured to transmit the first communications signal.