The Automatic-Control System as a Communication Channel

The science of communication was pursued in mathematical form much earlier than the science of control, since the former can be traced back at least to the mid nineteenth century when Kelvin solved the differential equation of the propagation of an electric signal along a cable of negligible inductance; and in the first quarter of the nineteenth century a number of well-known applied mathematicians (for example, Heaviside, Carson, Sobel, Nyquist) were associated with telecommunications. Moreover, Shannon's elaboration and consolidation of the mathematical theory of communication came before the major developments in automatic control. It is therefore profitable to examine whether any of the theorems or techniques which have been developed in connection with telecommunications can be applied to problems in automatic control.