squelch

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squelch

Electronics a circuit that cuts off the audio-frequency amplifier of a radio receiver in the absence of an input signal, in order to suppress background noise

squelch

[skwelch]
(electronics)
To automatically quiet a receiver by reducing its gain in response to a specified characteristic of the input.

squelch

squelchclick for a larger image
A simple squelch circuit.
A circuit in a radio receiver that keeps the volume down when no signal is being received, but the volume builds up as soon as a signal is received. The function of a squelch is to adjust the sensitivity of the receiver by eliminating unwanted weak signals that cause background noise such as static, hash, or hiss. Most squelch controls are automatic, but there are a few manual squelch controls, too. Squelch circuits are used in communications equipment, which have long periods of silence between transmissions.