What process converts an analog source into a discrete-time, analog-amplitude source?

The process that converts an analog source into a discrete-time, analog-amplitude source is known as sampling. Sampling involves taking measurements of the analog signal at regular intervals, which transforms the continuous signal into a series of discrete samples. This allows for the representation of the analog signal in a form that can be processed digitally while retaining the amplitude information.

Quantizing follows sampling and involves rounding the sampled values to a finite set of levels, typically related to a specific bit depth. Encoding, on the other hand, is the process of converting these quantized values into a specific format for transmission or storage, which doesn't apply until after sampling and quantizing have occurred. Graphing is a method for visually representing data but does not pertain to the conversion process itself. Thus, sampling is the correct choice as it specifically addresses the transition from continuous to discrete times in an analog context.