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# Long description

This figure is a graph of signal value against time. The horizontal axis extends from 0 to 1 units of time in increments of 0.1. The vertical axis is divided evenly into the same eight levels as in the previous figure, each represented by a three-bit binary number from 000 to 111. The distance between two levels is the quantisation interval.

One cycle of a sine wave is shown on the graph: it starts midway between the 011 and 100 levels at time 0, rises to reach the maximum 111 level at time 0.25, falls to cross the midway point again at time 0.5, falls further to reach the minimum 000 level at time 0.75, then rises back to the midway point at time 1. Overlaid on the sine wave is another line consisting of a series of steps, showing what the sine wave would look like if it were quantised to the eight levels. This stepped line remains at each level until the sine wave crosses the halfway point between that level and the one above or below it, at which point the stepped line rises or falls vertically to the new level.