The projective coordinates for calculation of load currents, presented in Chaps. 6–8, are analyzed. These coordinates, as a reference triangle, are introduced with the aid of characteristic regime points. Usually, the working values of load currents are much less, than the values of the characteristic regime currents. Therefore, the recalculation of load currents can lead to inadmissible errors. On the other hand, the high characteristic regime currents present technical difficulties when testing such circuits. The reasonable choice of more convenient projective coordinate systems, when the currents of the corresponding characteristic regimes are close to the working values of load currents, is given. The definitions of regime and its invariants, group properties of the regime changes, remain in these coordinate systems.