  We study the effects of dispersion in carrier waves on the properties of
soliton self--induced transparency (SIT) in two level media. We found
substantial impact of dispersion effects on typical SIT soliton features. For
example, the degree of SIT pulse velocity slowing down (acceleration) is
determined by the ratio of the incoming pulse frequency over atomic transition
frequency - $x=\omega/\omega_0$. Specifically, an immediate pulse stopping is
predicted for absorbing media when pulse duration time exceeds some critical
value. In the sharp line limit stopping may emerge only for frequency ratio
above unity, while for the inhomogeneously broadened systems it appears
irrespective of the value of $x$. Analysis performed on the basis of Mcall\&
Hahn \textit{Area theorem} implies that pulse stopping is achieved when Ber's
absorption coefficient approaches infinity, that is, pulse energy is fully
absorbed in the medium. In the case of amplifying media super-luminal motion is
predicted as in the case of resonance. However, there is a lowest value in the
frequency ratio below which the pulse velocity tends to the sub-luminal region.
These new features of the SIT phenomenon open novel ways on how it may be
exploited for the control of electromagnetic wave radiation in two-level media.
This may be achieved by varying frequency ratio.
