  We study the propagation of string fields (metric $G_{\mu\nu}$, Mawxell gauge
potential $A_{\mu}$, dilaton $\Phi$, and tachyon $T$) in a two-dimensional (2D)
charged black hole. It is shown that the tachyon is a propagating field both
inside and outside the black hole. This becomes infinitely blueshifted at the
inner horizon. We confirm that the inner horizon is unstable, whereas the outer
horizon is stable.
