  The phenomenological parameters of eclipsing binary stars, which are the
prototypes of the EA, EB and EW systems are determined using the expert complex
of computer programs, which realizes the NAV ("New Algol Variable") algorithm
(Andronov 2010, 2012) and its possible modifications are discussed, as well as
constrains for estimates of some physical parameters of the systems in a case
of photometric observations only, such as the degree of eclipse, ratio of the
mean surface brightnesses of the components. The half-duration of the eclipse
is 0.0617(7), 0.1092(18) and 0.1015(7) for Algol, $\beta$ Lyrae and W UMa,
respectively. The brightness ratio is 6.8$\pm$1.0, 4.9$\pm$1.0 and
1.15$\pm$0.13. These results show that the eclipses have distinct begin and end
not only in EA (as generally assumed), but also in EB and EW - type systems as
well. The algorithm may be applied to classification and study of the newly
discovered (or poorly studied) eclipsing variables based on own observations or
that obtained using photometric surveys.
