The RC filter-hard limiter-RC filter nonlinear system shown in Fig. 1 is the subject of this paper. Because of computational difficulties implicated in the analysis of the above system, only its response to the zero mean Gaussian system input has been analytically investigated [2,3,5]. An approximate output density has also been found for nonzero mean Gaussian, while verified to be "close" to the real one for finite means [4]. In the present paper, a close form of the system output density is obtained when the input mean tends to infinity. for that, xi-upcrossing methods were used.