The load impedance of a generator or the radiation impedance of a transducer can be controlled by a second active generator coupled to the first generator by a transmission line. The primary control variables are the relative magnitude and phase of the signals in each generator. A load impedance of any magnitude and phase, including negative resistance, can be obtained. The second generator is used as an active reflector and absorber. The theory is applicable to the case where the generators are underwater sound transducers and the line is a water‐filled tube.