Antex Electronics SX-26 Digital Audio Adapter - Manual (Page 6)

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To visualize the analog-to-digital conversion process, refer to
Figure 1. At the top is one cycle of an analog input signal wave.
We've used a simple sine wave to make visualization easier. In
this example, the signal has a peak-to-peak amplitude of 20 units,
measured by the scale on the left. The sampling frequency is
many times higher than the signal being sampled and is shown
along the bottom of Figure 1. Once for each cycle of the sampling
frequency, the sample-and-hold circuit "slices" the input signal,
allowing the quantizing circuit to generate a (digital) number equal
to the closest (of the 65,536 possible discrete values) quantization
value of the input signal at the time the sample is taken. This
repeats for each successive cycle of the sampling frequency and
the quantizer generates a continuous "bit stream" which
represents the quantized signal. The continuous stream of digital
audio information is converted into a digitally modulated signal
using a technique known as linear pulse code modulation.
Digital-to-analog conversion (used in playback) is the exact
opposite of the analog-to digital conversion process and is
illustrated in Figure 2.
Figure 1: Analog-to-Digital Conversion