  The system of equations of self-induced transparency (SIT) for extraordinary
wave in uniaxial anisotropic media by means of generalized reduction
perturbation method are transformed to the coupled nonlinear Schr\"odinger
equations. It is shown that in the theory of SIT the second derivatives have
significant role and leads to the formation of a vector $0\pi$ pulse
oscillating with the sum and difference of the frequencies. An explicit
analytical expressions for the profile and parameters of the nonlinear wave are
obtained. It is shown that along with scalar $2\pi$ pulse, the vector $0\pi$
pulse is also the basic pulse of SIT and the scalar $0\pi$ pulse of SIT is only
an approximation which can be considered in some special cases. The conditions
of the existence of the nonlinear extraordinary wave depends on the direction
of propagation. The profile of the vector $0\pi$ pulse in anisotropic crystal
of ruby is presented with characteristic parameters which usually met in
experiments.
