This chapter describes the frequency modulation in-band on-channel (FM IBOC) waveforms and presents the various configurations from which a broadcaster can choose in order to transmit digital audio or data in a manner that best supports the broadcaster's needs. It provides an overview of the DTS high definition (HD) Radio system design concepts and what it means to broadcasting systems. The chapter also describes the transmitted spectrum for each of the three digital waveform types. It examines the assignment of logical channels to the secondary sidebands and describes the intended application of the logical channels for each secondary service mode. The chapter reviews the modulation and spectral occupancy of the waveforms. It describes the processing necessary to convert the digital data in the active logical channels into an amplitude modulated IBOC waveform. HD Radio broadcasting represents a major departure in the way future broadcasting equipment and receivers must be built and function.