This document discusses various methods of modulating digital and analog data for transmission: 1. It describes digital-to-analog modulation techniques including amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK), and quadrature amplitude modulation (QAM). 2. It explains the relationships between bit rate, baud rate, and bandwidth for different modulation schemes. ASK, FSK, and PSK have baud rate equal to bit rate, while higher-order PSK and QAM can have higher bit rates through multiple bits per symbol. 3. Modems and standards like V.32, V.34, and V.90 are discussed in the context of mod