(under subclass 205) Subject matter wherein the receiver system includes means whereby the receiver is prevented from producing audio-frequency output in the total absence of an input signal or in the absence of a predetermined signal-noise ratio relationship.
(1) Note. The squelch means may be operated by signal energy in the receiver pass band, by noise quieting means, by a combination of the two, or means to prevent undesired variations in the output of the i.f., amplifier from causing a response in the output of the demodulator.
(2) Note. The amplitude limiting means found in this subclass is intended to ensure that the amplitude variations in the modulated wave input to the demodulator are an accurate representation of frequency modulation of the input exclusive of noise or other undesired effects and are not to be confused with the amplitude modulation elimination means found in subclasses 210+.
(3) Note. To complete the field of search for receivers in general utilizing muting or squelching means consult subclass 218.
(4) Note. The squelch means may be operated by an externally generated signal having special modulation characteristics; such systems are classified in subclasses 35.1+.
