Keith Dysart wrote:
When allowed to excite the black boxes with different
signals there are many ways to determine an internal
equivalent circuit. The question here was did the various
ways of making -j567 affect the results for sinusoidal
single frequency excitation.

Yes, it illustrated the two separate and different
IEEE definitions for "impedance", one a cause for
the voltage to current ratio and one a result of a
voltage to current ratio.
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73, Cecil http://www.w5dxp.com