Thus does not depend on , but on lag and we can write

The autocorrelation function of the out put is

                                                                     

is a function of lag m only and we write

       The mean-square value of the output process is

       Thus if is WSS then is also WSS.

        Taking the DTFT of we get
                                                            

This input-output relation in the frequency domain is illustrated in Figure 4.