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US 3,939,425 AGranted
Noise-squelching circuit using a phase-locked loop
AssigneeSony Corporation
InventorMasakatsu Toyoshima
Life of this patent
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Abstract
A noise-squelching circuit in which a phase-locked loop supplies an identifiable output signal that distinguishes between those times when the voltage-controlled oscillator in the loop is locked onto an incoming carrier, and those times when it is not. This identifiable signal controls a muting circuit to allow the information modulated onto the incoming carrier to pass through the muting circuit to an output terminal only when the loop is locked to an incoming signal but not when the loop is not locked onto a carrier.
Claims6
A noise-squelching circuit comprising:
- A. receiving means for receiving a modulated carrier signal within a predetermined frequency band;
- B. a phase-locked loop comprising a phase comparator, a low pass filter, and a voltage-controlled oscillator, said oscillator being controlled by an output signal from said filter to provide a carrier signal having a predetermined frequency related to the frequency of said modulated carrier signal when a modulated carrier signal is applied to said phase comparator;
- C. a demodulated signal path;
- and
- D. a muting circuit connected to said filter to be controlled by the output signal thereof and connected to said signal path to permit the passage of signals along said path only in response to a predetermined output signal level from said filter corresponding to a phase-locked condition of said loop.
2 more elements
Dependencies are inferred from the claim text.