  It is shown that the single-step periodic signal (periodic telegraph signal)
can not produce coherent stochastic resonance for diffusion on a segment with
one absorbing and one reflecting end points while the multi-step periodic
signal does. The general features of this process are exihibited. The resonant
frequency is found to decrease and the mean first passage time at resonant
frequency increases linearly, as we increase the length of the medium. The
cycle variable is shown to be the proper argument to express the first passage
time density function at resonance. A formula for first passage time density
function at resonance is derived in terms of two universal functions, which
clearly isolates its dependence on the length of the medium.
