n their own criteria and circumstances. However, it does cover the details of the pros and cons behind each approach, allowing the engineer to make better-in- formed decisions. We hope you enjoy reading and using this book as much as we enjoyed writing it! Part I: Fundamentals of Synchronization and Timing Chapter 1. Introduction to Synchronization and Timing In this chapter, you will learn the following: Overview of time synchronization: Covers the basic concepts behind time, beginning with some history and coming forward to the present day. What is synchronization and why is it needed?: Introduces the different types of synchroniza- tion, namely frequency, phase, and time of day. What is time?: Covers the concepts of time, the currently used timescales, such as TAI and UTC, and modern sources of time. How can GPS provide timing and synchronization?: Provides a basic overview of the satel- lite systems that are widely used to distribute time. Accuracy versus precision versus stability: Covers these three concepts, vital to the discus- sion of the quality with which time is kept, transported, and used. This chapter begins with a look at the historical record to help you understand how the world defines time today and why it is defined that way. Although seemingly a very simple concept, the implementation and practical applications of time are very involved. A few searches on Wikipedia on the subject of time quickly leads down rabbit holes of details, SO this text will stick to the highlights. After an introduction to time, the focus moves to synchronization, addressing why you might need it and what happens when it goes wrong. The term "synchronization" covers several different types (frequency, phase, and time), SO it is important to understand which type of synchronization is re- quired for any specific use case, why that application might need it, and how you accomplish it. 1.1 Overview of Time Synchronization In medieval times, before anybody had any form of accurate timepiece, a village might use a clock- to