This principle provides the theoretical foundation for converting analog signals to digital signals. The principle says that it is possible to reliably represent analog signal if the signal is sampled at twice the maximum frequency of the signal.
Nyquist theorem is applied for building the current telecommunications infrastructure.
The maximum voice frequency for telephone communications is set at 4KHz. This means that the analog voice signals need to be sampled at 8KHz. However, there has been tremendous progress in communications technologies since then. It is now possible to achieve almost the same telephone grade voice quality at about 4Kbps. This means that at 64Kbps, the current telecommunication network is 16 times less efficient for carrying voice traffic, if it were designed using the most current technologies.