US4127846A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tone signal detecting circuit
Assignee: NEC Corp
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Filing: 1977-11-25
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Granted: 1978-11-28
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Expires: 1997-11-25
Abstract
Abstract A tone signal detecting circuit for use in a paging receiver or the like employs an N-path filter in place of an active filter to facilitate circuit integration. The circuit includes a clock signal generating circuit responsive to a first control signal for selecting and reading out one of plural clock signals of a frequency equal to N (N being an integer equal to or greater than 2) times the frequency of the plural tone signals. The N-path filter has a prescribed rise and fall time and selects and responds to a tone signal in accordance with a clock signal from the clock signal generating circuit. A low-pass filter having prescribed frequency characteristics removes harmonic signals of the tone signals contained in the output of the N-path filter. A tone designating circuit responsive to a second control signal is connected to the low-pass filter and changes its frequency characteristics. A detector is connected to the output of the low-pass filter, and control circuits are responsive to the output of the detector to generate the first and second control signals.
Inventors
- 👤 Toshihiro Mori
- 👤 Takashi Oda
- 👤 Koichi Nagata
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 19:35
CPC Classifications
H; H04; H04W; H04W88/00; H04W88/02; H04W88/022; H04W88/025; H04W88/027
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
195 words
A tuneable tone signal detecting circuit for sequentially receiving and passing a plurality of tone signals in a predetermined sequence comprising: a first means responsive to a first control signal for selecting and providing as an output one of a plurality of clock signals of a frequency equal to N, N being an integer equal to or greater than 2, times the frequency of said plurality of tone signals; an N-path filter having a prescribed energy buildup and decay rate for selecting and responding to said plurality of tone signals in accordance with the output of said first means; a first filter having prescribed frequency characteristics for removing harmonic signals of each of said plurality of tone signals contained in the output of said N-path filter; a second means connected to said first filter for changing said frequency characteristics in response to a second control signal, a detector connected to said first filter and responsive to each of said plurality of tone signals sequentially passing said N-path filter for providing a detected output; and a third means connected to said detector and responsive to said detecting signals for providing said first and second control signals.
Claim 2
Dependent Claim
195 words
A tuneable tone signal detecting circuit for sequentially receiving and passing a plurality of tone signals in a predetermined sequence comprising: a first means responsive to a first control signal for selecting and providing as an output one of a plurality of clock signals of a frequency equal to N, N being an integer equal to or greater than 2, times the frequency of said plurality of tone signals; an N-path filter having a prescribed energy buildup and decay rate for selecting and responding to said plurality of tone signals in accordance with the output of said first means; a first filter having prescribed frequency characteristics for removing harmonic signals of each of said plurality of tone signals contained in the output of said N-path filter; a second means connected to said first filter for changing said frequency characteristics in response to a second control signal, a detector connected to said first filter and responsive to each of said plurality of tone signals sequentially passing said N-path filter for providing a detected output; and a third means connected to said detector and responsive to said detecting signals for providing said first and second control signals.
Claim 3
Dependent Claim
48 words
A tone signal detecting circuit as claimed in claim 1 which further comprises an indicator means connected to said detector and responsive to a detecting signal corresponding to the final one of said plurality of tone signals for indicating the reception of a prescribed series of tone signals.
Claim 4
Dependent Claim
47 words
A tone signal detecting circuit as claimed in claim 1 wherein said first means comprises a signal generator and a fifth means responsive to said first control signal for dividing the frequency of the output of said signal generator at varying ratios to generate said clock signals.
Claim 5
Dependent Claim
88 words
A tone signal detecting circuit as claimed in claim 1 wherein said N-path filter comprises a resistor for receiving said plurality of said tone signals at one terminal thereof and N first capacitors connected in parallel to the other terminal of said resistor and switches each connected in series to one of said N capacitors for being opened and closed in a cyclic sequence by the frequency of said clock signals, and wherein said fourth means simultaneously closes all of said switches in response to said detected output.
Claim 6
Dependent Claim
30 words
A tone signal detecting circuit as claimed in claim 1 wherein said first filter is a low-pass filter comprising at least of a resistor and a plurality of second capacitors.
Claim 7
Dependent Claim
23 words
A tone signal detecting circuit as claimed in claim 5 which further comprises means for connecting said second means to said second capacitors.
References Cited (Backward Citations)
US3670242A
Cited
US3882466A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-11-27 | 1982-05-29 | 1982-11-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-11-27 | 1986-05-29 | 1986-11-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-11-27 | 1990-05-29 | 1990-11-28 | $7700.00 | Window Closed / Lapsed |