See modulation and carrier. Vary the Amplitude In AM modulation, the voltage (amplitude) of the carrier is varied by the incoming signal. In this example, the modulating wave implies an analog signal.

This tutorial explains the fundamentals of time-, frequency-, and modulation-domain analysis from the perspective of several examples.

For example, a standard broadcast amplitude modulation signal looks like Figure 18 where the high frequency carrier signal always has an envelope that looks like the low frequency modulating signal.

One of the most basic digital modulation schemes, amplitude shift keying (ASK), is frequently used in simple wireless systems such as RF car remotes and tire pressure monitoring systems.