What is the primary function of a squelch?

The primary function of a squelch is to mute the receiver audio when a signal is not present. Squelch circuits are commonly found in two-way radios and receivers to prevent the speaker from producing noise in the absence of a radio signal. By setting the squelch level, users can filter out background noise, allowing them to hear only when a desired signal is strong enough to be heard above that noise level. This makes for a more pleasant and focused listening experience, especially in environments with significant static or interference.

The other options, while related to various aspects of radio operation, do not accurately describe the function of squelch. Reducing key clicks in a CW transmitter pertains to signal purity and clarity during Morse code transmissions, eliminating parasitic oscillations deals with stability in RF amplifiers, and reducing interference from impulse noise involves different noise reduction techniques. Each has its own specific function in the context of radio communications, but they do not describe the primary role of squelch.