There are three basic types of modulations for transmission of sound over a digital medium:
Amplitude modulation (AM)
Frequency modulation (FM)
Phase modulation (PM)
Amplitude modulation uses a voltage change to increase or decrease the size of peaks and valleys. For example, AM radio stations broadcast their programs using amplitude modulation.
Frequency modulation changes frequencies to cause increases and decreases in the space between waves. For example, FM radio stations broadcast their programs using frequency modulation.
Phase modulation shifts the point at which a wave begins by delaying the moment at which a wave begins transmission. Modern analog modems use a constellation of phase and amplitude combinations to represent ...