Since the mid-1970s, digital methods of transmitting data have slowly but surely replaced the older, more conventional analog ones. Today, thanks to the availability of fast, low-cost analog-to-digital (A /D) and digital-to-analog (D /A) converters and high-speed digital signal processors, most electronic communications is digital.

This chapter begins with the reasons for using digital transmission. Then the concepts and operation of A /D and D /A converters are summarized. Next, pulse modulation techniques are described, and the chapter concludes with an introduction to digital signal processing (DSP), techniques.