There are two forms of implementing spacing in spaced repetition. The areoles are spaced evenly along the ribs, approximately apart. They are usually spaced uniformly and crossed by the spirals. Therefore, meridians are equally spaced along a given parallel. Note that they are not proportionally spaced along the surface. The wing pivot points are significantly spaced far apart. Chloroplast contains evenly spaced and ungrouped thylakoids. This is as desired for equally spaced angular momenta. In other cases, the hour-lines are not spaced evenly, even though the shadow rotates uniformly. Arrays may also be formed using numbers of very closely spaced microphones. In the diagram shown, the gridlines are spaced one unit distance apart. This is because the hour angles are equally spaced around the dial. Multiple miniature banana connectors are usually spaced on -inch centers. When walking or trotting, the tracks are spaced roughly apart. Unfortunately the resonant modes are not exactly equally spaced due to dispersion.