McLuhan was greatly struck by an observation in Norbert Wiener’s 1950 The Human Use Of Human Beings  concerning “the electron valve “:

it is 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. (173)

He had read Wiener’s book soon after it was published and then immediately wrote to Wiener relating this observation to his own field of English literature:

Your account of the uses of the vacuum tube in heavy industry is an exact description of the poetic techniques of Joyce and Eliot in constructing their works. Their use of allusion as situational analogy effects an enormous amplification of power from small units, at the same time that it permits an unrivalled precision. (McLuhan to Norbert Wiener, March 28, 1951, Norbert Wiener Papers M.I.T.)

In essays from the early 1950s¹ McLuhan went on to specify further both how “a tiny amount of energy can be exactly controlled or stepped up instantly to very high potentials”² and how this principle applied to language and communication in general. Wiener had traced the idea back to Edison³, but for McLuhan it could be seen at work throughout “the whole history of culture”:

When current is too weak for direct flow, it can, in a vacuum tube, be used as signal voltage on the grid of the tube. Then every variation in the shape of the wave will be faithfully reproduced in the output wave of the tube. Thus a tiny amount of energy can be exactly controlled or stepped up instantly to very high potentials. Now metaphor has always had the character of the cathode-anode circuit, and the human ear has always been a grid, mesh, or, as Joyce calls it in Finnegans Wake, Earwicker. But Joyce was the first artist to make these aspects of language and communication explicit. In so doing, he applied the principles of electronics to the whole history of culture.²

The central point was that control of an electric circuit or of sense requires a break through a repurposing takes place. As McLuhan would later put it: “the gap is where the action is”.

With electronification the flow is taken out of the wire and into the vacuum tube circuit, which confers freedom and flexibility such as are in metaphor and in words themselves.⁵

Such a break in flow occurs in all language and communication:

Metaphor means a carrying across. All speech is metaphoric because any oral sound is a gesture towards externalizing an inner gesture of the mind. (…) [Likewise] writing is metaphor for sound. It translates, or metamorphizes the audible into the visual. There is necessarily discontinuity in metaphor. There has to be a leap from one situation to another. (‘Radio and Television vs. The ABCED-Minded’, Explorations 5, 1955) 

Now Bohm and Hiley offer comparable considerations of what they call “active information” in The Undivided Universe:⁶

• new properties of matter (…) are revealed by the quantum theory. The first of these new properties can be seen by noting that the quantum potential is not changed when we multiply the field ψ by an arbitrary constant.(…) This means that the effect of the quantum potential is independent of the strength (i.e. the intensity) of the quantum field but depends only on its form.
• consider a ship on automatic pilot being guided by radio waves. Here, too, the effect of the radio waves is independent of their intensity and depends only on their form. The essential point is that the ship is moving with its own energy, and that the form of the radio waves is taken up to direct the much greater energy of the ship.
• The basic idea of active information is that a form having very little energy enters into and directs a much greater energy. The activity of the latter is in this way given a form similar to that of the smaller energy.
• consider a radio wave whose form carries a signal. The sound energy we hear in the radio does not come directly from the radio wave itself which is too weak to be detected by our senses. It comes from the power plug or batteries which provide an essentially unformed energy that can be given form (i.e. in-formed) by the pattern carried by the radio wave. This process is evidently entirely objective and has nothing to do with our knowing the details of how this happens. The information in the radio wave is potentially active everywhere, but it is actually active, only where and when it can give form to the electrical energy which, in this case, is in the radio.
• in the process of cell growth it is only the form of the DNA molecule that counts, while the energy is supplied by the rest of the cell (and indeed ultimately by the environment as a whole). Moreover, at any moment, only a part of the DNA molecule is being ‘read’ and giving rise to activity. The rest is potentially active and may become actually active according to the total situation in which the cell finds itself. While we are bringing out (…) the objective aspects of [active] information, we do not intend to deny its importance in subjective human experience. [On the contrary]⁷, we wish to point out that even in this domain, the notion of active information still applies.
• it seems that the general idea of something like active information is (…) needed for an ontological explanation of quantum theory.
• The wave function is defined in the configuration space of all the particles. (…) Information is ordered in the configuration space rather than in the ordinary space of three dimensions.  The fact that the wave function is in configuration space implies that we have to look more carefully into the meaning of active information in such a context. First of all we may consider its implications for all the motions of the particles. These now respond in a correlated way to what is, in effect, a common pool of information. 

“Configuration space” considered as “a common pool of information” and as differentiated from three dimensional space is closely related to Bohm’s notion of the “implicate order” of possibility.⁸