The eye diagram is a very useful and practical tool for analyzing, evaluating, diagnosing and correcting errors in digital communication systems or indeed any digital/wireless system. The premise is fairly simple. Using the eye diagram a number of valuable parameters may be extracted at a glance. These parameters play a critical role in the transmission and reception of data. An intuitive understanding of the eye diagram is essential for good design technique and analysis of systems. Simulation of the eye diagram and its measurement can be better understood if one knows the underlying technique of eye diagram construction. A brief expose of this tool can be found at http://www.signalpro.biz. > engineer’s corner.