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