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Patent US3743950A successfully refreshed from Google Patents.
US3743950A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Threshold detector for a voice frequency receiver
Assignee: U S Holding Co Inc
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Filing: 1972-03-03
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Granted: 1973-07-03
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Expires: 1992-03-03
Abstract
Abstract A threshold detector is disclosed which provides an output signal in response to a sinusoidal signal from a band pass filter while the sinusoidal signal has a voltage level equal to or above a reference voltage. The detector employs an operational amplifier as a first comparator or detector circuit to provide a pulse in response to each excursion of the sinusoidal signal above the threshold value. Current from the pulse is used to charge a capacitor in an RC circuit to a level above the reference voltage. A second operational amplifier is connected to the RC circuit to provide the desired constant output voltage so long as the stored voltage is equal to or above the reference voltage. Feedback from the output of the second operational amplifier to the input of the first operational amplifier is used to adjust the reference voltage to a level which makes the threshold detector insensitive to noise input associated with the sinusoidal signal.
Inventors
- 👤 D Sellari
- 👤 H Frost
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:13
CPC Classifications
H; H04; H04Q; H04Q1/00; H04Q1/18; H04Q1/30; H04Q1/44; H04Q1/444; H04Q1/45; H04Q1/453
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
144 words
A threshold detector, responsive to a sinusoidal signal from a band pass filter to supply input for a voice frequency receiver comprising first comparator means coupled to compare voltages and provide an output voltage when a sinusoidal input voltage on a first terminal is equal to, or greater than, a reference voltage on a second terminal, storage means coupled to receive and store said output voltage, second comparator means coupled to the storage means and to the reference voltage on the second terminal for comparing the stored output voltage with said reference voltage and providing a second output voltage when the stored output voltage is equal to or exceeds the reference voltage, and means coupling said second output voltage to the second terminal to modify the reference voltage and prevent an erratic second output voltage due to noise associated with said sinusoidal input voltage.
Claim 2
Dependent Claim
144 words
A threshold detector, responsive to a sinusoidal signal from a band pass filter to supply input for a voice frequency receiver comprising first comparator means coupled to compare voltages and provide an output voltage when a sinusoidal input voltage on a first terminal is equal to, or greater than, a reference voltage on a second terminal, storage means coupled to receive and store said output voltage, second comparator means coupled to the storage means and to the reference voltage on the second terminal for comparing the stored output voltage with said reference voltage and providing a second output voltage when the stored output voltage is equal to or exceeds the reference voltage, and means coupling said second output voltage to the second terminal to modify the reference voltage and prevent an erratic second output voltage due to noise associated with said sinusoidal input voltage.
Claim 3
Dependent Claim
78 words
In a threshold detector as claimed in claim 1 means for completing a connection to a band pass filter, means for assuring an accurate and stable reference voltage to enable preservation of desired bandwidth in a band pass filter, said means for assuring an accurate and stable reference voltage including a voltage divider formed of low tolerance metal film resistors from which the reference voltage is taken together with a high gain operational amplifier in the first comparator.
Claim 4
Dependent Claim
63 words
A threshold detector as claimed in claim 1, in which the reference voltage is held accurate and stable, to preserve the bandwidth of a band pass filter feeding said threshold detector, a high gain operational amplifier in said first comparator, and a voltage divider formed of low tolerance metal film resistors through which the reference voltage is supplied from a stable voltage source.
Claim 5
Dependent Claim
46 words
A threshold detector as claimed in claim 1, in which the first comparator means provides an output voltage in the form of a pulse, and the storage means includes an RC circuit responsive to said pulse to establish a voltage source for the second comparator means.
Claim 6
Dependent Claim
61 words
A threshold detector as claimed in claim 1, in which the output voltage produced by the first comparator means is a pulse at a voltage level above the reference voltage level, and the storage means includes an RC circuit responsive to said pulse to establish a voltage source for the second comparator means at a higher level than said reference voltage.
Claim 7
Dependent Claim
43 words
A threshold detector as claimed in claim 1, in which said first comparator provides a positive pulse, and unidirectional means are coupled to receive said positive pulse and transmit it to said storage means to provide a positive potential to said storage means.
Claim 8
Dependent Claim
51 words
A threshold detector as claimed in claim 1, in which said first comparator provides a positive pulse, said storage means responds to said positive pulse to provide a positive potential to said second comparator, and said second comparator responds to said positive potential to provide an output having a negative potential.
Claim 9
Dependent Claim
36 words
A threshold detector as claimed in claim 1, in which the first comparator means includes a first operational amplifier, the storage means includes an RC circuit, and the second comparator means includes a second operational amplifier.
Claim 10
Dependent Claim
71 words
A threshold detector as claimed in claim 1, in which the first comparator means provides an output voltage in the form of a positive pulse, the storage means includes an RC circuit responsive to said pulse to establish a voltage source for the second comparator means, and the second comparator means provides a constant output voltage while the voltage on said RC circuit is equal to or exceeds the reference voltage.
Claim 11
Dependent Claim
96 words
A threshold detector as claimed in claim 1, in which the first comparator provides an output voltage in the form of a pulse each time the sinusoidal input voltage rises to a level equal to, or greater than, the reference voltage, the storage means, in response to said pulses, maintains the stored voltage above a critical level for so long as the pulses continue and are separated by a particular time period, and the second comparator provides an output signal for so long as the stored voltage maintains a level equaling or exceeding the reference voltagE.
Claim 12
Dependent Claim
98 words
A threshold detector as claimed in claim 1, in which the first comparator includes a first operational amplifier which provides an output voltage in the form of a pulse each time the sinusoidal input voltage exceeds the reference voltage, said operational amplifier supplies each pulse at an amplitude greater than the reference voltage, the storage means includes an RC circuit which responds to each pulse to renew the stored output voltage, and the second comparator includes a second operational amplifier responsive to provide an output voltage for so long as said stored output voltage exceeds said reference voltage.
Claim 13
Dependent Claim
42 words
A threshold detector as claimed in claim 1, in which the first terminal of the threshold detector is coupled to a band pass filter, and said first terminal of the comparator exhibits high input impedance to minimize loading effect on the filter.
Claim 14
Dependent Claim
40 words
A threshold detector as claimed in claim 1, in which said first and second comparators comprise operational amplifiers, and the reference voltage is provided from a stable voltage source over a voltage divider formed of low tolerance metal film resistors.
References Cited (Backward Citations)
US3119984A
Cited
US3686577A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-02 | 1977-01-01 | 1977-07-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-02 | 1981-01-01 | 1981-07-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-02 | 1985-01-01 | 1985-07-03 | $7700.00 | Window Closed / Lapsed |