Book excerpt: Pulse Code Modulation Techniques brings together the theory and practice of PCM at the physical layer, where the "bits meet the silicon", so to speak. The key topics of symbol encoding, detection and synchronization are discussed, in detail, both from a theoretical and a practical standpoint. Topics which have been largely absent in text books, such as multiplexing, formatting and format synchronization, are also considered. Although PCM evolved as a communication technology, it has become an important technology in data recording. In a sense, magnetic or optical media are just specialized communication media and the key technologies discussed in this book are just as important to recording applications as to communications. PCM codes used for magnetic recording applications are discussed along with traditional communication codes. The design, analysis and implementation of a PCM system requires knowledge of very specific techniques associated with detection, synchronization and coding. The techniques have evolved from both ad hoc methods and complex theory. One of the goals of this book is to bridge the gap between theory and practice in the key techniques. Matched filters are not only discussed theoretically, but means for implementing them are also considered. The same is true with symbol synchronization.