A discrete signal or **discrete-time signal** is a time series consisting of a sequence of quantities. In other words, it is a time series that is a function over a domain of discrete integers. Each value in the sequence is called a sample.

Unlike a continuous-time signal, a discrete-time signal is not a function of a continuous argument; however, it may have been obtained by sampling from a continuous-time signal. When a discrete-time signal is a sequence corresponding to uniformly spaced times, it has an associated sampling rate; the sampling rate is not apparent in the data sequence, so may be associated as a separate data item.

## Acquisition[]

Discrete signals may have several origins, but can usually be classified into one of two groups:

- By acquiring values of an analog signal at constant or variable rate. This process is called sampling.
- By accumulating a variable over time. For example, the number of people taking a certain elevator every day.

## Video[]

thumb|300px|right

## Digital signals[]

A digital signal is a discrete-time signal that takes on only a discrete set of values.

The process of converting a continuous-valued discrete-time signal to a digital (discrete-valued discrete-time) signal is known as quantization. This process, also known as analog-to-digital conversion, loses information (by truncating or rounding the sample values). That is, discrete-valued signals are always an approximation to the original continuous-valued signal.

Common practical digital signals are represented as 8-bit (256 levels), 16-bit (65,536 levels), 32-bit (4.3 billion levels), and so on, though any number of quantization levels is possible, not just powers of two.