Which description best matches a digital signal?

Which description best matches a digital signal?

• A. A An analog signal that has not been sampled
• B. B A continuous-time signal with unquantized amplitudes
• C. C A sequence of numbers representing sampled and quantized values
• D. D A purely continuous-time signal

Answer: (C)

Digital signals are representations that are discrete in time and amplitude. They come from sampling a continuous-time signal at regular intervals and quantizing the amplitude to a finite set of levels, producing a sequence of numbers that encode the signal. This is exactly what a digital signal is: a series of numeric values representing the sampled, quantized amplitudes. In contrast, an analog signal that has not been sampled remains continuous in time; a continuous-time signal with unquantized amplitudes is still analog; and a purely continuous-time signal does not produce discrete numeric values.

Digital signals are representations that are discrete in time and amplitude. They come from sampling a continuous-time signal at regular intervals and quantizing the amplitude to a finite set of levels, producing a sequence of numbers that encode the signal. This is exactly what a digital signal is: a series of numeric values representing the sampled, quantized amplitudes. In contrast, an analog signal that has not been sampled remains continuous in time; a continuous-time signal with unquantized amplitudes is still analog; and a purely continuous-time signal does not produce discrete numeric values.