Anytime, anywhere, anything can be taken as the motto and objective of digital communications. Anytime means that one can communicate on a 24/7 basis; anywhere states this communication can take place in any geographical location, at minimum one no longer is tied to being close to one's land line; anything implies that not only traditional voice and video but also other messages can be transmitted over the same channel, principally text, and not only individually but in combination. In large part digital communication systems over the past three decades have achieved the three objectives. Text messaging in all its forms, such as email, internet access, etc., is a reality. Webcasting and podcasting are becoming common. All parts of the globe are connected to the world wide communication system provided by the Internet.

Perhaps, and arguably just as important, a fourth “any” can be added, anybody. Though perhaps not as well developed as the first three, digital communication has the potential to make communication affordable to everyone. One feature of digital circuitry is that its cost, relative to its capability, keeps dropping dramatically. Thus though analog communication could achieve the above objectives, digital communications, due to this increasingly low cost, flexibility, robustness, and ease of implementation, has become the preferred technology.

This text is an introduction to the basics of digital communication and is meant for those who wish a fundamental understanding of important aspects of digital communication design.