US3902123A
Expired / Lapsed
US
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Digital circuit for determining if signal source consists primarily of noise or contains information
Assignee: Cincinnati Electronics Corp
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Filing: 1973-11-30
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Granted: 1975-08-26
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Expires: 1993-11-30
Abstract
Abstract A digital squelch circuit responds to a band limited audio output signal of a radio receiver to count the number of cycles of the source per unit length of time. In response to the count being respectively above and below a predetermined value, the audio signal source is decoupled from and gated to an output terminal. The audio signal source is gated to the output terminal for a predetermined period subsequent to termination of the count with the predetermined time being less than a pre-established value in order to prevent squelching in the period between adjacent words of a voice source.
Inventors
- 👤 Johannes A F Oomen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 00:21
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/34; H03G3/342
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
237 words
A digital squelch circuit responsive to a band limited audio output signal of a radio receiver comprising first counter means advanced in response to the signal to repeatedly count the number of cycles of the source in successive time periods having predetermineD durations and for deriving an output signal each time the count in one of the periods exceeds a predetermined value indicative of no information signal being derived from the receiver, second counter means advanced once each of the time periods, means for resetting the second counter means each time no signal is derived from the first counter means during a time period, the second counter means deriving an output signal in response to a predetermined number of the time periods occurring prior to resetting of the second counter means, the time interval of the predetermined number of periods being slightly greater than the typical time interval between word utterances of a speaker, a latching circuit respectively driven to first and second states in response to (a) no signal being derived from the first counter means during a time interval and (b) the output signal of the second counter means, and a gate circuit responsive to the receiver output signal and an output signal of the latching circuit for respectively enabling and disabling coupling of the receiver output signal to an output terminal in response to the latching circuit being in the first and second states.
Claim 2
Dependent Claim
237 words
A digital squelch circuit responsive to a band limited audio output signal of a radio receiver comprising first counter means advanced in response to the signal to repeatedly count the number of cycles of the source in successive time periods having predetermineD durations and for deriving an output signal each time the count in one of the periods exceeds a predetermined value indicative of no information signal being derived from the receiver, second counter means advanced once each of the time periods, means for resetting the second counter means each time no signal is derived from the first counter means during a time period, the second counter means deriving an output signal in response to a predetermined number of the time periods occurring prior to resetting of the second counter means, the time interval of the predetermined number of periods being slightly greater than the typical time interval between word utterances of a speaker, a latching circuit respectively driven to first and second states in response to (a) no signal being derived from the first counter means during a time interval and (b) the output signal of the second counter means, and a gate circuit responsive to the receiver output signal and an output signal of the latching circuit for respectively enabling and disabling coupling of the receiver output signal to an output terminal in response to the latching circuit being in the first and second states.
Claim 3
Dependent Claim
79 words
The circuit of claim 1 further including means for deriving first, second and third time displaced pulses during each period, said first pulse occurring in each period slightly before the second pulse, the latching circuit and the second counter resetting means being responsive to the sampled output of the first counter means, means for resetting the first counter means in response to the second pulse, and means for advancing the second counter means in response to the third pulse.
Claim 4
Dependent Claim
51 words
The circuit of claim 2 wherein the means for deriving the first, second and third time displaced pulses includes a clock source for advancing a third counter means, said third counter means including first, second and third output terminals on which are respectively derived the first, second and third output pulses.
Claim 5
Dependent Claim
28 words
The circuit of claim 1 further including rectifier means responsive to the signal for deriving a d.c. power supply voltage for energizing active elements of the squelch circuit.
Claim 6
Dependent Claim
225 words
A circuit to indicate if a band limited audio signal contains information, in the form of a voice signal or a tone, or consists primarily of noise, comprising first counter means advanced in response to the signal to repeatedly count the number of cycles of the source in successive time periods having predetermined durations and for deriving an output signal each time the count in one of the periods exceeds a predetermined value indicative of no information signal being derived from the receiver, second counter means advanced once each of the time periods, means for resetting the second counter means each time no signal is derived from the first counter means during a time period, the second counter means deriving an output signal in response to a predetermined number of the time periods occurring prior to resetting of the second counter means, the time interval of the predetermined number of periods being slightly greater than the typical time interval between word utterances of a speaker, a latching circuit respectively driven to first and second states in response to (a) no signal being derived from the first counter means during a time period and (b) the output signal of the second counter means, the latching circuit being in the first and second states respectively indicating that the audio signal does and does not contain the information.
Claim 7
Dependent Claim
225 words
A circuit to indicate if a band limited audio signal contains information, in the form of a voice signal or a tone, or consists primarily of noise, comprising first counter means advanced in response to the signal to repeatedly count the number of cycles of the source in successive time periods having predetermined durations and for deriving an output signal each time the count in one of the periods exceeds a predetermined value indicative of no information signal being derived from the receiver, second counter means advanced once each of the time periods, means for resetting the second counter means each time no signal is derived from the first counter means during a time period, the second counter means deriving an output signal in response to a predetermined number of the time periods occurring prior to resetting of the second counter means, the time interval of the predetermined number of periods being slightly greater than the typical time interval between word utterances of a speaker, a latching circuit respectively driven to first and second states in response to (a) no signal being derived from the first counter means during a time period and (b) the output signal of the second counter means, the latching circuit being in the first and second states respectively indicating that the audio signal does and does not contain the information.
Claim 8
Dependent Claim
79 words
The circuit of claim 5 further including means for deriving first, second and third time displaced pulses during each period, said first pulse occurring in each period slightly before the second pulse, the latching circuit and the second counter resetting means being responsive to the sampled output of the first counter means, means for resetting the first counter means in response to the second pulse, and means for advancing the second counter means in response to the third puLse.
Claim 9
Dependent Claim
51 words
The circuit of claim 6 wherein the means for deriving the first, second and third time displaced pulses includes a clock source for advancing a third counter means, said third counter means including first, second and third output terminals on which are respectively derived the first, second and third output pulses.
Claim 10
Dependent Claim
228 words
A circuit to indicate if a band limited audio signal contains information, in the form of a voice signal or a tone, or consists primarily of noise, comprising first counter means advanced in response to the signal to repeatedly count the number of cycles of the source in successive time periods having predetermined durations and for deriving an output signal each time the count in one of the periods exceeds a predetermined value indicative of no information signal being derived from the receiver, a clock source, second counter means advanced in response to the clock source, means for resetting the second counter means each time no signal is derived from the first counter means during a time period, the second counter means deriving an output signal in response to a predetermined number of the time periods occurring prior to resetting of the second counter means, the time interval of the predetermined number of periods being slightly greater than the typical time interval between word utterances of a speaker, a latching circuit respectively driven to first and second states in response to (a) no signal being derived from the first counter means during a time period and (b) the output signal of the second counter means, the latching circuit being in the first and second states respectively indicating that the audio signal does and does not contain the information.
Claim 11
Dependent Claim
228 words
A circuit to indicate if a band limited audio signal contains information, in the form of a voice signal or a tone, or consists primarily of noise, comprising first counter means advanced in response to the signal to repeatedly count the number of cycles of the source in successive time periods having predetermined durations and for deriving an output signal each time the count in one of the periods exceeds a predetermined value indicative of no information signal being derived from the receiver, a clock source, second counter means advanced in response to the clock source, means for resetting the second counter means each time no signal is derived from the first counter means during a time period, the second counter means deriving an output signal in response to a predetermined number of the time periods occurring prior to resetting of the second counter means, the time interval of the predetermined number of periods being slightly greater than the typical time interval between word utterances of a speaker, a latching circuit respectively driven to first and second states in response to (a) no signal being derived from the first counter means during a time period and (b) the output signal of the second counter means, the latching circuit being in the first and second states respectively indicating that the audio signal does and does not contain the information.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-25 | 1979-02-24 | 1979-08-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-25 | 1983-02-24 | 1983-08-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-25 | 1987-02-24 | 1987-08-26 | $7700.00 | Window Closed / Lapsed |