Some relativistic invariant systems of differential equations

We define a new class of partial differential equations of first order (complex covariantly equipped systems of equations), which are invariant with respect to (pseudo)orthogonal changes of Cartesian coordinates of (pseudo)euclidian space. It is shown that for pseudoeuclidian spaces of signature $(1,n-1)$ covariantly equipped systems of equation can be written in the form of Friedrichs symmetric hyperbolic systems of equations of first order. We prove that Maxwell and Dirac model equations belong to the class of covariantly equipped systems of equations.