Squelch
（重定向自Squelch circuit）
In telecommunications, squelch is a circuit function that acts to suppress the audio (or video) output of a receiver in the absence of a sufficiently strong desired input signal. Squelch is widely used in two-way radios and radio scanners to suppress the sound of channel noise when the radio is not receiving a transmission. Squelch can be 'opened', which allows all signals entering the receivers discriminator tap to be heard. This can be useful when trying to hear distant, or otherwise weak signals.