Weakly activated signaling cascades can be modeled as linear systems. The
input-to-output transfer function and the internal gain of a linear system,
provide natural measures for the propagation of the input signal down the
cascade and for the characterization of the final outcome. The most efficient
design of a cascade for generating sharp signals, is obtained by choosing all
the off rates equal, and a ``universal'' finite optimal length.Comment: 27 pages, 10 figures, LaTeX fil