Which modulation technique uses frequency variations to encode information?

Frequency Modulation (FM) is a modulation technique that employs variations in the frequency of the carrier wave to encode information. This method allows the amplitude of the carrier signal to remain constant while the frequency shifts in accordance with the input signal, which can carry the desired information, such as audio or data.

In FM, the amount of frequency deviation is directly related to the amplitude of the incoming signal, allowing for the transmission of a more complex waveform without distortion. This type of modulation is noted for its resilience to noise, making it particularly useful in radio broadcasting and communication systems where clarity and fidelity are crucial.

In contrast, other techniques like Amplitude Modulation (AM) encode information through variations in the amplitude of the carrier wave, while Phase Modulation (PM) involves changes to the phase of the carrier signal. Time Division Multiplexing (TDM) is not a modulation technique but a method of transmitting multiple signals over a shared medium by allocating distinct time slots for each signal, thus it does not fit into the category of frequency variation encoding.