Sampling and Aliasing
Reconstruction of a continuous signal from samples taken at sampling interval T is done by some sort of interpolation, such as the Whittaker–Shannon interpolation formula. Mathematically, that process is often modelled as the output of a lowpass filter whose input is a Dirac comb whose teeth have been weighted by the sample values. Such a comb is equivalent to the product of a comb and the original continuous signal. That mathematical abstraction is often described as "sampling" for purposes of introducing the subjects of aliasing and the Nyquist-Shannon sampling theorem.
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