What is modulation in communications equipment?

Modulation is a fundamental concept in communications equipment that refers to the technique used to encode information onto a carrier wave for transmission. This process is essential because it allows information (such as voice, video, or data) to be transmitted over various media, including air and cables, by altering the characteristics of a carrier wave.

When modulation is applied, certain properties of the carrier wave—such as its amplitude, frequency, or phase—are varied in accordance with the information being sent. This makes it possible to efficiently transmit signals over long distances without significant loss of quality.

Other techniques mentioned in the options, while related to communications, do not encapsulate the primary function of modulation. For example, increasing bandwidth or filtering signals are important concepts in signal processing, but they do not directly define what modulation is. Similarly, converting electrical signals to sound pertains more to the transduction process rather than the encoding of information for transmission. Thus, the role of modulation in preparing a signal for effective transmission makes this definition the most accurate in the context of communications equipment.