US3758860A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Selective calling squelch circuit for receiving systems
Assignee: Motorola Solutions Inc
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Filing: 1972-01-17
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Granted: 1973-09-11
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Expires: 1992-01-17
Abstract
Abstract A receiver, decoder and switch connected to an (audio) output stage with a first band pass filter connected to the decoder and supplying a signal to an OR gate only when a message is properly decoded by the decoder and a second band pass filter connected to the decoder and supplying a signal to the OR gate only when white noise, or an improperly decoded signal, is present at the decoder. The presence of a signal from the first filter or the absence of a signal from the second filter enables the OR gate and activates the switch to allow the signal to pass from the decoder to the output stage.
Inventors
- 👤 W Braun
- 👤 A Leitich
- 👤 A Brown
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 17:32
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/34; H03G3/344
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
258 words
A system, including a selective calling squelch circuit, for receiving transmitted signals including information, having a specified band of frequencies, coded to produce a relatively wide band of frequencies with an average amplitude across the band which differs substantially from the average amplitude across the band of the information, said system comprising: a. receiver means adapted to receive said transmitted signals and supply an output of coded information; b. a decoder coupled to said receiver means for receiving the output therefrom and decoding the coded information; c. first switch means having an input, connected to receive the decoded information from said decoder, and an output; d. first band pass filter means passing a band of frequencies lying within the specified band of frequencies of the information and having an input, connected to receive the output from said decoder, and an output; e. second band pass filter means passing a relatively narrow band of frequencies coinciding with a portion of the band of frequencies of the coded information and excluding the band of frequencies of the information, said second filter means having an input, connected to receive the output from said decoder, and an output; and f. gate means connected to said first switch means and to the outputs of said first and second filter means for activating said first switch means to pass the information to the output thereof upon the occurrence of one of the passage of information through said first filter means and the absence of the passage of a signal through said second filter means.
Claim 2
Independent Claim
258 words
A system, including a selective calling squelch circuit, for receiving transmitted signals including information, having a specified band of frequencies, coded to produce a relatively wide band of frequencies with an average amplitude across the band which differs substantially from the average amplitude across the band of the information, said system comprising: a. receiver means adapted to receive said transmitted signals and supply an output of coded information; b. a decoder coupled to said receiver means for receiving the output therefrom and decoding the coded information; c. first switch means having an input, connected to receive the decoded information from said decoder, and an output; d. first band pass filter means passing a band of frequencies lying within the specified band of frequencies of the information and having an input, connected to receive the output from said decoder, and an output; e. second band pass filter means passing a relatively narrow band of frequencies coinciding with a portion of the band of frequencies of the coded information and excluding the band of frequencies of the information, said second filter means having an input, connected to receive the output from said decoder, and an output; and f. gate means connected to said first switch means and to the outputs of said first and second filter means for activating said first switch means to pass the information to the output thereof upon the occurrence of one of the passage of information through said first filter means and the absence of the passage of a signal through said second filter means.
Claim 3
Dependent Claim
44 words
A system as set forth in claim 1 including in addition first means interposed between said first filter means and said gate means and second means interposed between said second filter means and said gate means for converting signals passing therethrough to DC signals.
Claim 4
Dependent Claim
16 words
A system as set forth in claim 1 wherein the gate means includes an ''''OR'''' gate.
Claim 5
Dependent Claim
70 words
A system as set forth in claim 1 wherein the average amplitude of the information across the band thereof exceeds the average amplitude of the coded information across the band thereof and the gate means includes circuitry responsive to signals from the first filter means having an average amplitude across the band thereof which exceeds the average amplitude of the coded information across the band thereof by a predetermined amount.
Claim 6
Dependent Claim
60 words
A system as set forth in claim 1 wherein the band of frequencies of the coded information is approximately 0 to 30 KHz, the first filter means includes components tuned to pass a band of frequencies approximately 350 to 2,700 hertz and the second filter means includes components tuned to pass a band of frequencies approximately 50 to 150 hertz.
Claim 7
Dependent Claim
28 words
A system as set forth in claim 1 wherein the decoder includes a shift-register/exclusive-or curcuit and the coded information is a scrambled binary bit stream or digital signal.
Claim 8
Dependent Claim
99 words
A system as set forth in claim 1 including in addition: transmitting means adapted to transmit signals including information, having the specified band of frequencies, coded to produce a relatively wide band of frequencies with an average amplitude across the band which differs substantially from the average amplitude across the band of the information; coding means attached to said transmitting means for providing the coded information to be transmitted; and connecting means electrically attaching the first band pass filter means to said coding means for frequency limiting information applied to said coding means to the specified band of frequencies.
Claim 9
Dependent Claim
23 words
A system as set forth in claim 7 including in addition signal utilization means Connected to the output of said first switch means.
Claim 10
Dependent Claim
47 words
A system as set forth in claim 8 including in addition a second switch means coupled to the transmitting means and the signal utilization means and including circuitry for deactivating said transmitting means during reception of signals and circuitry for deactivating said signal utilization means during transmission.
Claim 11
Dependent Claim
252 words
A transmit-receive system comprising: a. receiving means adapted to receive transmitted signals including information, having a specified band of frequencies, coded to produce a relatively wide band of frequencies with an average amplitude across the band which differs substantially from the average amplitude across the band of the information; b. a decoder coupled to said receiving means for receiving the output therefrom and decoding the coded information; c. switch means having an input, connected to receive the decoded information from said decoder, and an output; d. squelch means, including band pass filter means for passing a band of frequencies substantially equal to the specified band of frequencies of the information, connected to said decoder and to said switch means for activating said switch means to pass to the output of said switch means information received at the input of said switch means only when the information from said decoder is correctly decoded; e. transmitting means adapted to transmit signals including information, having the specified band of frequencies, coded to produce a relatively wide band of frequencies with an average amplitude across the band which differs substantially from the average amplitude across the band of the information; f. coding means attached to said transmitting means for providing the coded information to be transmitted; and g. switch means attached to said squelch means and said coding means for electrically connecting said band pass filter means to said coding means to frequency limit information applied to said coding means to the specified band of frequencies.
Claim 12
Dependent Claim
252 words
A transmit-receive system comprising: a. receiving means adapted to receive transmitted signals including information, having a specified band of frequencies, coded to produce a relatively wide band of frequencies with an average amplitude across the band which differs substantially from the average amplitude across the band of the information; b. a decoder coupled to said receiving means for receiving the output therefrom and decoding the coded information; c. switch means having an input, connected to receive the decoded information from said decoder, and an output; d. squelch means, including band pass filter means for passing a band of frequencies substantially equal to the specified band of frequencies of the information, connected to said decoder and to said switch means for activating said switch means to pass to the output of said switch means information received at the input of said switch means only when the information from said decoder is correctly decoded; e. transmitting means adapted to transmit signals including information, having the specified band of frequencies, coded to produce a relatively wide band of frequencies with an average amplitude across the band which differs substantially from the average amplitude across the band of the information; f. coding means attached to said transmitting means for providing the coded information to be transmitted; and g. switch means attached to said squelch means and said coding means for electrically connecting said band pass filter means to said coding means to frequency limit information applied to said coding means to the specified band of frequencies.
References Cited (Backward Citations)
US3496467A
Cited
US3613003A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-10 | 1977-03-12 | 1977-09-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-10 | 1981-03-12 | 1981-09-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-10 | 1985-03-12 | 1985-09-11 | $7700.00 | Window Closed / Lapsed |