Patent US6115608A successfully refreshed from Google Patents.
US3974450A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dual frequency FM receiver
Assignee: UNIDEN Corp AN IN CORP
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Filing: 1975-07-16
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Granted: 1976-08-10
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Expires: 1995-07-16
Abstract
Abstract A receiver is disclosed which will receive signals on either one of two closely spaced frequencies. The receiver is of the superheterodyne type and has a local oscillator frequency midway between the two frequencies which the receiver is tuned to. The receiver also includes a tone squelch circuit which mutes the audio unless a tone is received for a period of time.
Inventors
- 👤 Charles Cunningham, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:36
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/005; H03G1/00; H03G1/02; H04; H04B; H04B1/00; H04B1/06; H04B1/16; H04B1/26; H04B1/28; H04B7/00; H04B7/02; H04B7/12
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
156 words
A superheterodyne receiver for receiving frequency modulated signals on one of two frequencies which are less than 500 kHz apart comprising: a. a local oscillator which operates at a frequency which is both independent of received signals and essentially midway between the two frequencies, said local oscillator being controlled in frequency by a piezoelectric crystal; b. R. F. signal receiving means having a bandpass broad enough for reception of signals on either of the two frequencies; c. a mixer for mixing signals from said R. F. signal receiving means with the output of said local oscillator; d. an I F bandpass filter coupled to the output of said mixer for preventing signals below 10 kHz and above 250 kHz from passing through; e. a frequency modulation detector connected to the output of said I F filter; and f. transducer means connected to the output of said frequency modulation detector for producing audio from the detected signal.
Claim 2
Dependent Claim
156 words
A superheterodyne receiver for receiving frequency modulated signals on one of two frequencies which are less than 500 kHz apart comprising: a. a local oscillator which operates at a frequency which is both independent of received signals and essentially midway between the two frequencies, said local oscillator being controlled in frequency by a piezoelectric crystal; b. R. F. signal receiving means having a bandpass broad enough for reception of signals on either of the two frequencies; c. a mixer for mixing signals from said R. F. signal receiving means with the output of said local oscillator; d. an I F bandpass filter coupled to the output of said mixer for preventing signals below 10 kHz and above 250 kHz from passing through; e. a frequency modulation detector connected to the output of said I F filter; and f. transducer means connected to the output of said frequency modulation detector for producing audio from the detected signal.
Claim 3
Dependent Claim
50 words
The receiver of claim 1 which additionally includes tone squelch means for preventing production of audio until a tone is received and for thereafter permitting production of audio, said tone squelch means including a manually operable reset switch means for again preventing production of audio until another tone is received.
Claim 4
Dependent Claim
22 words
The receiver of claim 2 in which said tone squelch means can be manually readily disabled to allow continuous monitoring of audio.
Claim 5
Dependent Claim
18 words
The receiver of claim 3 in which said tone squelch means is responsive to a 1050 Hz tone.
Claim 6
Dependent Claim
36 words
The receiver of claim 1 in which said receiver is for receiving frequency modulated signals on either 162.4 MHz or 162.55 MHz and in which said local oscillator operates at a frequency of essentially 162.475 MHz.
Claim 7
Dependent Claim
24 words
The receiver of claim 5 in which said I F bandpass filter passes essentially only frequencies between about 55 kHz and about 95 kHz.
Claim 8
Dependent Claim
50 words
The receiver of claim 5 which additionally includes tone squelch means for preventing production of audio until a tone is received and for thereafter permitting production of audio, said tone squelch means including a manually operable reset switch means for again preventing production of audio until another tone is received.
Claim 9
Dependent Claim
22 words
The receiver of claim 7 in which said tone squelch means can be manually readily disabled to allow continuous monitoring of audio.
Claim 10
Dependent Claim
23 words
The receiver of claim 8 in which said IF bandpass filter passes essentially only frequencies between about 55 kHz and about 95 kHz.
Claim 11
Dependent Claim
18 words
The receiver of claim 9 in which said tone squelch means is responsive to a 1050 Hz tone.
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) | 1979-08-10 | 1980-02-09 | 1980-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-10 | 1984-02-09 | 1984-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-10 | 1988-02-09 | 1988-08-10 | $7700.00 | Window Closed / Lapsed |