Which of the following describes the muting of receiver audio controlled solely by the presence or absence of an RF signal?

The term that describes the muting of receiver audio controlled solely by the presence or absence of an RF signal is carrier squelch. This system functions by monitoring the strength of the incoming radio frequency (RF) signal. When the signal exceeds a certain threshold level, the squelch circuit opens, allowing audio to pass through so the operator can hear the transmission. If no significant RF signal is detected—meaning the signal is below the threshold—the squelch remains closed, muting the receiver audio.

This method is widely used to reduce noise and prevent the receiver from emitting sound when no transmission is present. Unlike tone squelch or CTCSS, which require the presence of a specific sub-audible tone or coded signal to open the squelch, carrier squelch does not depend on such additional tones and operates strictly based on the strength of the RF signal.