How is information applied to the carrier in FM communications?

In FM (Frequency Modulation) communications, information is applied to the carrier by varying the frequency of the carrier wave according to the instantaneous amplitude of the modulating signal. The primary mechanism by which this occurs involves altering the frequency, which encodes the information being transmitted.

The correct choice involves comprehending the dual aspects of modulation techniques. In FM, while the amplitude of the carrier remains relatively constant, the frequency is what changes to convey the desired information. This modulation can be distinguished between different types of sideband operations; for example, Single-Sideband (SSB) modulation allows transmission of either the upper sideband (USB) or lower sideband (LSB) while eliminating the carrier and one of the sidebands entirely. This contrasts with Double-Sideband (DSB) operations which transmit both sidebands but are less efficient.

Thus, the correct answer captures the essence of how FM communication encodes information primarily through frequency variation, accommodating both DSB and SSB operations, while maintaining that amplitude remains unchanged when transmitting signals.