This chapter has laid the foundations for good sampling practice, in that it has shown why it is necessary to sample band-limited signals at a rate which is above than given rate. In a complementary manner, it has also identified why sampling at great speed is unnecessary, being wasteful of bandwidth and storage space, thereby adding nothing useful to the information content of that same signal. The subtleties associated with the discrete and the digitised signal, and examined various means of analog to digital and digital to analog conversion. Finally, some methods that might be adopted when designing digital signal acquisition and transmission systems are also discussed. Armed with this knowledge, one can now move forward to consider the design of off-line and real-time DSP algorithms and systems hardware.