A method is developed for calculating the probability density function

of the output of an

filter when the input is a particular kind of random telegraph wave. The method makes use of a computer to determine the numerical values of the coefficients in two series solutions, one of which contains a logarithm, of a fourth-order linear differential equation. The constants of integration are determined from the boundary conditions by a procedure that involves a summation of the series. Representative values and curves of

are presented, and the generality of the computer method is discussed briefly,