Transformerless data transmission device e.g for two-wire telephone or transmission-lines - uses at least one control circuit for correcting output- side DC-supply voltage of transmission device to ensure that the DC-supply voltage level does not drop

摘要

A data transmission device has a transmission device (1-3) for generating an output signal on the transmission line (A,B), the output signal being comprised of a transmitted signal and a DC-supply (input terminal) voltage. At least one control circuit (5-8) is provided for correcting the output-side DC-supply voltage of the transmission device (1-3, such that the level of the DC-supply voltage does not decline. The control circuit specifically comprises a measurement device (4) for measuring the DC-voltage level at the output of the transmission device, and an addition-device (7) for adding the measured DC-voltage level to the transmitted signal.