- Nyquist Rule is one of the mathematical expressions.

- While sampling the frequency, the sampling frequency is multiplied twice.

- The signal should not contain a Fourier spectrum with sine or cosine above the frequency.

- The signal can be reconstructed by sampling at twice the frequency.

- The signal can not be reconstructed if the signal is not sampled at twice the frequency.

- Nyquist is required only for digital signal processing but not for analog singnal processing.