Patent US3866151A successfully refreshed from Google Patents.
US3866151A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Specific frequency signal detecting circuit
Assignee: NEC Corp
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Filing: 1973-03-13
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Granted: 1975-02-11
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Expires: 1993-03-13
Abstract
Abstract An improved specific frequency signal detecting circuit useful, for example, in a telephone channel includes a bandpass circuit and a band-rejection circuit, the difference in the detected outputs of which is compared with a threshold reference voltage. Detection of the specific frequency signal occurs when the difference voltage exceeds the reference voltage. The bandpass circuit includes an amplitude limiter to prevent malfunctioning or false detecting when formant components are present in the specific frequency signal band.
Inventors
- 👤 Mutsunari Tajima
- 👤 Isao Komatsu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 23:31
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/04; H04B3/10
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
147 words
In a specific frequency signal detecting circuit comprising: means for passing full-range frequency components in a transmission frequency band and for delivering a first d.c. signal representative of the lEvel of said full-range frequency components; means for attenuating specific frequency components in said frequency band, for passing the remaining frequency components in said frequency band, and delivering a second d.c. signal representative of the level of said remaining frequency components; means for subtracting said second d.c. signal from said first d.c. signal; and means for generating a detection signal when the output of said subtracting means exceeds a given threshhold value, thereby to detect a specific frequency signal contained in said specific frequency components; the improvement comprising an amplitude limiting means in said full-range frequency components passing means for restricting the output level of said full-range frequency components passing means to a value below a predetermined level.
Claim 2
Dependent Claim
147 words
In a specific frequency signal detecting circuit comprising: means for passing full-range frequency components in a transmission frequency band and for delivering a first d.c. signal representative of the lEvel of said full-range frequency components; means for attenuating specific frequency components in said frequency band, for passing the remaining frequency components in said frequency band, and delivering a second d.c. signal representative of the level of said remaining frequency components; means for subtracting said second d.c. signal from said first d.c. signal; and means for generating a detection signal when the output of said subtracting means exceeds a given threshhold value, thereby to detect a specific frequency signal contained in said specific frequency components; the improvement comprising an amplitude limiting means in said full-range frequency components passing means for restricting the output level of said full-range frequency components passing means to a value below a predetermined level.
Claim 3
Dependent Claim
170 words
A specific frequency signal detecting circuit comprising: means for passing full-range frequency components in a transmission frequency band and for delivering a first d.c. signal representative of the level of said full-range frequency components, including amplitude limiting means for causing the gain of said full-range frequency components passing means to be a non-linear multiplier decreasing with increasing signal level; means for attenuating specific frequency components in said frequency band, for passing the remaining frequency components in said frequency band, and delivering a second d.c. signal representative of the level of said remaining frequency components; means for subtracting said second d.c. signal from said first d.c. signal; and means for generating a detection signal when the output of said subtracting means exceeds a given threshold value, thereby to detect a specific frequency signal contained in said specific frequency components whereby the detecting circuit is prevented from malfunctioning by externally introduced circuit noise whose level is near said given threshhold value when measured at the input of said detection signal generating means.
Claim 4
Dependent Claim
170 words
A specific frequency signal detecting circuit comprising: means for passing full-range frequency components in a transmission frequency band and for delivering a first d.c. signal representative of the level of said full-range frequency components, including amplitude limiting means for causing the gain of said full-range frequency components passing means to be a non-linear multiplier decreasing with increasing signal level; means for attenuating specific frequency components in said frequency band, for passing the remaining frequency components in said frequency band, and delivering a second d.c. signal representative of the level of said remaining frequency components; means for subtracting said second d.c. signal from said first d.c. signal; and means for generating a detection signal when the output of said subtracting means exceeds a given threshold value, thereby to detect a specific frequency signal contained in said specific frequency components whereby the detecting circuit is prevented from malfunctioning by externally introduced circuit noise whose level is near said given threshhold value when measured at the input of said detection signal generating means.
Claim 5
Dependent Claim
209 words
A specific frequency signal detecting circuit comprising: means for passing full-range frequency components in a transmission frequency band and for delivering a first d.c. signal representative of the level of said full-range frequency components, said full-range frequency components passing means including an amplifier receiving an input signal, amplitude limiting means having a non-linear gain decreasing with increasing signal level, and a detector, said amplifier, amplitude limiting means and said detector being connected in series; means for attenuating specific frequency components in said frequency band, for passing the remaining frequency components in said frequency band, and delivering a second d.c. signal representative of the level of said remaining frequency components, said specific frequency attenuating means including a band-rejection filter for rejecting said specific frequency components, an amplifier, and a detector, said band-rejection filter, amplifier and detector being connected in series; means for subtracting said second d.c. signal from said first d.c. signal; and means for generating a detection signal when the output of said subtracting means exceeds a given threshold value, thereby to detect a specific frequency signal contained in said specific frequency components without malfunctioning when externally introduced circuit noise measured at the input of said detection signal generating means is at a level near said given threshold value.
Claim 6
Dependent Claim
209 words
A specific frequency signal detecting circuit comprising: means for passing full-range frequency components in a transmission frequency band and for delivering a first d.c. signal representative of the level of said full-range frequency components, said full-range frequency components passing means including an amplifier receiving an input signal, amplitude limiting means having a non-linear gain decreasing with increasing signal level, and a detector, said amplifier, amplitude limiting means and said detector being connected in series; means for attenuating specific frequency components in said frequency band, for passing the remaining frequency components in said frequency band, and delivering a second d.c. signal representative of the level of said remaining frequency components, said specific frequency attenuating means including a band-rejection filter for rejecting said specific frequency components, an amplifier, and a detector, said band-rejection filter, amplifier and detector being connected in series; means for subtracting said second d.c. signal from said first d.c. signal; and means for generating a detection signal when the output of said subtracting means exceeds a given threshold value, thereby to detect a specific frequency signal contained in said specific frequency components without malfunctioning when externally introduced circuit noise measured at the input of said detection signal generating means is at a level near said given threshold value.
References Cited (Backward Citations)
US3076939A
Cited
US3163717A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-02-10 | 1978-08-12 | 1979-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-10 | 1982-08-12 | 1983-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-10 | 1986-08-12 | 1987-02-11 | $7700.00 | Window Closed / Lapsed |