From The Human Use of Human Beings: Cybernetics and Society, 1950, 145-146 (emphasis added):

The most flexible universal apparatus for amplifying small energy-levels into high energy-levels is the vacuum tube, or electron valve (…) that  (…) originated in Edison’s greatest scientific discovery (…).
He observed that when an electrode was placed inside an electric lamp, and was taken as electrically positive with respect to the filament, then a current would flow, if the filament were heated, but not otherwise. Through a series of inventions by other people, this led to a more effective way than any known before of controlling a large current by a small voltage. This is the basis of the modern radio industry, but it is also an industrial tool which is spreading widely into new fields. It is thus no longer necessary to control a process at high energy-levels by a mechanism in which the important details of control are carried out at these levels.¹ It is quite possible to form a certain pattern of behavior response at levels much lower even than those found in usual radio sets, and then to employ a series of amplifying tubes to control by this apparatus a machine as heavy as a steel-rolling mill. The work of discriminating and of forming the pattern of behavior for this is done under conditions in which the power losses are insignificant, and yet the final employment of this discriminatory process is at arbitrarily high levels of power.
It will be seen that this is an invention which alters the fundamental conditions of industry (…) The study of the pattern of behavior is transferred to a special part of the instrument in which power-economy is of very little importance. We have thus deprived of much of their importance the dodges and devices previously used to insure that a mechanical linkage should consist of the fewest possible elements, as well as the devices used to minimize friction and lost motion. The design of machines involving such parts has been transferred from the domain of the skilled shopworker to that of the research-laboratory man; and in this he has all the available tools of circuit theory to replace a mechanical ingenuity of the old sort. Invention in the old sense has been supplanted by the intelligent employment of certain laws of nature. The step from the laws of nature to their employment has been reduced by a hundred times.