The processes of propagation and absorption of electron cyclotron extraordinary modes in a Tokamak type plasma slab are studied by means of a wave-dynamical system of differential equations in which temperature effects are taken into account. Also the mode conversion of the incoming wave into Bernstein waves is described by the propagation equations and is analysed in the parameter space together with its effects on the global absorption. Similarities and discrepancies between the results of the numerical integration of the full-wave system and those provided by the WKB approximation are discussed as a function of the electron density and temperature.