Modulation refers to the application of information onto a carrier signal by varying one or more of the signal’s basic characteristics (frequency, amplitude or phase); the conversion of a signal from its original (e.g., digital) format to analog format. Specific types include:
• Amplitude modulation (AM)
• Adaptive differential pulse code modulation (ADPCM)
• Frequency modulation (FM)
• Pulse amplitude modulation (PAM)
• Pulse code modulation (PCM)
• Pulse width modulation (PWN); also called pulse duration modulation, or PDM