A novel method for testing a communications circuit is disclosed. The method includes the following steps: (a) connecting an internal balanced circuit to a well-balanced resistor network; (b) measuring a first plurality of real and imaginary components of the voltages with the internal balanced circuit connected to the well-balanced resistor network; (c) calculating an error for the internal balanced circuit based on the first plurality of voltages; (d) connecting the internal balanced circuit to the communications circuit; (e) measuring a second plurality of real and imaginary components of the voltages with the internal balanced circuit connected to the communications circuit; and (f) calculating a corrected balance for the communications circuit based on the second plurality of voltages and the error for the internal balanced resistor network. A novel device and software program that incorporates this novel method are also disclosed.