Which of the following is not considered a type of modulation?

Modulation is a technique used in communication systems to encode information onto a carrier wave, allowing for the transmission of data over various mediums. The three common types of modulation include Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).

Amplitude Modulation involves varying the amplitude of the carrier signal in accordance with the information being sent. Frequency Modulation alters the frequency of the carrier wave, while Phase Modulation changes the phase angle of the carrier signal corresponding to the transmitted information.

In the context of this question, "Power Modulation" is not a recognized standard type of modulation used in communication systems. While concepts related to power might be involved in the broader context of signal transmission, they do not correspond to a specific method of encoding information by modifying the carrier wave. Hence, it is accurately identified as the option that does not belong in the list of types of modulation.