What type of modulator employs an electromechanical device for varying frequency?

The modulator that employs an electromechanical device for varying frequency is a mechanical modulator. This type of modulator uses physical components, often involving moving parts, to create changes in frequency as a function of mechanical movement. The electromechanical aspect refers to the way electrical energy is transformed into mechanical motion, which in turn alters the modulation characteristics of the signal being transmitted. This could involve components like gears, levers, or other mechanical systems that operate under the influence of electrical signals.

Other types of modulators, such as electrical, digital, or analog, primarily focus on manipulating signal parameters through electronic circuits or digital processes rather than through mechanical systems. For instance, electrical modulators work through electrical circuit components, and digital modulators utilize binary data to impact modulation but do not involve the physical movement characteristic of a mechanical modulator. Therefore, understanding the unique role of mechanical systems in this context highlights why the mechanical modulator is the appropriate choice.