Varies the amplitude or height of a signal to represent the binary data

Changes the signal into a carrier signal

When noise occurs it normally affects amplitude of the signal meaning this keying method is more susceptible to signal loss

Varies the frequency of the signal.

One frequency can represent the 0 bits and another can represent the 1 bits

Varies the phase of the signal

A phase change can represent the 0 and no change in phase can represent a 1