US4145580A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multi-frequency signal receiver
Assignee: NEC Corp
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Filing: 1978-01-23
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Granted: 1979-03-20
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Expires: 1998-01-23
Abstract
Abstract A multi-frequency signal receiver for use in tone signalling circuits is disclosed. The receiver includes a plurality of channel band pass filters having mutually independent pass bands, each of which receives the input signal. Threshold detectors are connected to the outputs of the channel bandpass filters as is a variable threshold circuit. The variable threshold circuit includes a peak hold circuit and an attenuator for generating a threshold value for the detectors. A rectifier and integrator circuit rectifies an output which is weighted compared with the output of the peak hold circuit to produce a timing signal. The timing signal is used to gate the output of the detectors.
Inventors
- 👤 Kouichi Hasegawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 13:25
CPC Classifications
H; H04; H04Q; H04Q1/00; H04Q1/18; H04Q1/30; H04Q1/44; H04Q1/444; H04Q1/45; H04Q1/453
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
135 words
A multi-frequency signal receiver adapted to receive an input signal consisting of at least two frequency tones selected out of more-than-two predetermined frequencies, comprising: filter means for receiving said input signal and having mutually independent pass bands at said frequencies; detector means coupled with said filter means for sensing the presence of a signal output at each of said frequencies; a variable threshold circuit coupled to said filter means for detecting the maximum value among the output signals of said filter means and for generating a threshold value for said detector means; an integrator circuit for integrating said input signal means for effecting weighted comparison between the outputs of said variable threshold circuit and said integrator circuit to provide a timing pulse; and means for gating outputs of said detector means by said timing pulse.
Claim 2
Dependent Claim
135 words
A multi-frequency signal receiver adapted to receive an input signal consisting of at least two frequency tones selected out of more-than-two predetermined frequencies, comprising: filter means for receiving said input signal and having mutually independent pass bands at said frequencies; detector means coupled with said filter means for sensing the presence of a signal output at each of said frequencies; a variable threshold circuit coupled to said filter means for detecting the maximum value among the output signals of said filter means and for generating a threshold value for said detector means; an integrator circuit for integrating said input signal means for effecting weighted comparison between the outputs of said variable threshold circuit and said integrator circuit to provide a timing pulse; and means for gating outputs of said detector means by said timing pulse.
Claim 3
Dependent Claim
166 words
In a multi-frequency signal receiver of the type adapted to receive an input signal consisting of at least two frequency tones selected out of more-than-two predetermined frequencies, said receiver including filter means for receiving said input signal and having mutually independent pass bands at said frequencies and detector means coupled with said filter means for sensing the presence of a signal output at each of said frequencies, the improvement comprising: a variable threshold circuit coupled to said filter means for detecting the maximum value among the output signals of said filter means and for generating a threshold value for said detector means; a rectifier and integrator circuit for rectifying and integrating said input signal; comparing means coupled to said variable threshold circuit and said integrator circuit for effecting weighted comparison between the outputs of said variable threshold circuit and said integrator circuit to provide a timing pulse; and gating means coupled to said detector means for gating outputs of said detector means by said timing means.
Claim 4
Dependent Claim
166 words
In a multi-frequency signal receiver of the type adapted to receive an input signal consisting of at least two frequency tones selected out of more-than-two predetermined frequencies, said receiver including filter means for receiving said input signal and having mutually independent pass bands at said frequencies and detector means coupled with said filter means for sensing the presence of a signal output at each of said frequencies, the improvement comprising: a variable threshold circuit coupled to said filter means for detecting the maximum value among the output signals of said filter means and for generating a threshold value for said detector means; a rectifier and integrator circuit for rectifying and integrating said input signal; comparing means coupled to said variable threshold circuit and said integrator circuit for effecting weighted comparison between the outputs of said variable threshold circuit and said integrator circuit to provide a timing pulse; and gating means coupled to said detector means for gating outputs of said detector means by said timing means.
Claim 5
Dependent Claim
22 words
The multi-frequency signal receiver as recited in claim 2, further comprising an attenuator connected to the output of said variable threshold circuit.
Claim 6
Dependent Claim
86 words
The multi-frequency signal receiver as recited in claim 2, wherein said variable threshold circuit comprises: a plurality of differential input operational amplifiers having respective first input terminals connected to corresponding outputs of said filter means and second input terminals connected in common, a plurality of diodes each connected between the output terminal and the second input terminal of a corresponding one of said differential input operational amplifiers, and a capacitor connected to the common connection of said second input terminals for storing a peak detected voltage.
Claim 7
Dependent Claim
31 words
The multi-frequency signal receiver as recited in claim 2, wherein said filter means comprises a plurality of multi-stage second order negative feedback type band-pass filters, one for each of said frequencies.
References Cited (Backward Citations)
US3961143A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-03-19 | 1982-09-18 | 1983-03-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-03-19 | 1986-09-18 | 1987-03-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-03-19 | 1990-09-18 | 1991-03-20 | $7700.00 | Window Closed / Lapsed |