Excerpt from the original CRV Manual by Paul H. Smith
An opening or an open space; Hole, gap, gap, abyss, slit. In radar, the electronic gate that controls the width and dispersion pattern of the emitted signal or wave.
After a proper Stage I Ideogram/A/B sequence has been executed, the aperture (which was at its narrowest point during Stage I) opens to accommodate Stage II information. Not only does this allow the more detailed sensory information to pass through to the viewer, but it is accompanied by a correspondingly longer signal “loiter” time–the information comes in more slowly, and is less concentrated. Towards the end of Stage II, and approaching the threshold of Stage III, the aperture begins to expand even further, allowing the acquisition of dimensionally related information.