US4939765A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interlock circuit for preventing corruption of telephone line signals
Assignee: Fluke Corp
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Filing: 1989-11-24
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Granted: 1990-07-03
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Expires: 2009-11-24
Abstract
Abstract Corruption of communication signals on a telephone line by the direct (low impedance) interfacing of test equiupment to the line is precluded by a protective interlock circuit, which prevents the test set from seizing the line if data traffic is present. The interlock circuit is coupled between the line circuit to be accessed and the test equipment, and includes a multiple band frequency detector, which monitors the line for signals lying within (in and out-of-audio) frequency bands. Should the detector identify any traffic within its sensitivity range (out of the audio band) during the interval of a timing pulse produced by the closure of a switch, the logic level applied to combinational logic will change state and prevent the generation of a test set enabling signal. The test set enabling signal is normally coupled to a `line-seize` transistor circuit within the test set, so that, without this enabling signal, the test set is effectively locked-out from the line and data cannot be corrupted. Should the frequency detector not have produced an out of audio band detection signal after the expiration of the timing pulse, the combinational logic circuit and an associated flip-flop generate an output signal for enabling the test equipment to seize the line. The flip-flop remains set and the logic level of the output signal is maintained until the line is no longer seized by the test equipment.
Inventors
- 👤 Dean L. Benjamin
- 👤 Wayne K. Wong
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 21:17
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/22; H04M3/26; H04M3/28; H04M3/30; H04M1/00; H04M1/24; H04Q; H04Q1/00; H04Q1/18; H04Q1/30; H04Q1/44; H04Q1/442
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
88 words
An interface circuit for controllably coupling a telephone line to line test equipment comprising: first means, to which a telephone line is to be coupled, for controllably monitoring said line for the presence of communication signals on said line; second means, coupled to said first means, for causing said first means to monitor said line for the presence of communication signals on said line and, in the absence thereof, generating an output signal in response to which said line test equipment may cause said line to be seized.
Claim 2
Dependent Claim
88 words
An interface circuit for controllably coupling a telephone line to line test equipment comprising: first means, to which a telephone line is to be coupled, for controllably monitoring said line for the presence of communication signals on said line; second means, coupled to said first means, for causing said first means to monitor said line for the presence of communication signals on said line and, in the absence thereof, generating an output signal in response to which said line test equipment may cause said line to be seized.
Claim 3
Dependent Claim
46 words
An interface circuit according to claim 1, wherein said first means comprises means for monitoring said line for the presence of communication signals in respectively different frequency bands and providing an output in response to the presence of communication signals in any of said frequency bands.
Claim 4
Dependent Claim
82 words
An interface circuit according to claim 2, wherein said second means comprises switch means for generating an enabling signal in response to which said first means is enabled to monitor said line and gate means coupled to receive said enabling signal and the output of said first means and generating said output signal after the generation of said enabling signal by said switch means in the absence of communication signals on said line, but otherwise preventing the generation of said output signal.
Claim 5
Dependent Claim
32 words
An interface circuit according to claim 3, wherein said second means comprises means for maintaining the generation of said output signal until the line is no longer seized by said test equipment.
Claim 6
Dependent Claim
30 words
An interface circuit according to claim 1, further including third means for controllably coupling said test equipment to said line in response to said second means generating said output signal.
Claim 7
Dependent Claim
42 words
An interface circuit according to claim 5, wherein said second means comprises means for maintaining the generation of said output signal until the line is no longer seized by said test equipment and thereafter controllably decoupling said test equipment from said line.
Claim 8
Dependent Claim
29 words
An interface circuit according to claim 1, further comprising third means for causing said second means to generate said output signal irrespective of the operation of said first means.
Claim 9
Dependent Claim
88 words
An interface circuit according to claim 1, wherein said second means comprises first switch means for generating a first enabling signal in response to which said first means is enabled to monitor said line and gate means coupled to receive said first enabling signal and the output of said first means and generating said output signal after the generation of said first enabling signal by said first switch means in the absence of communication signals on said line, but otherwise normally preventing the generation of said output signal.
Claim 10
Dependent Claim
67 words
An interface circuit according to claim 8, further comprising third means for causing said second means to generate said output signal irrespective of the operation of said first means, said third means including second switch means for generating a second enabling signal, and wherein said gate means includes means, responsive to said first and second enabling signals, for causing said second means to generate said output signal.
Claim 11
Dependent Claim
112 words
An interface circuit for controllably coupling a telephone line to line test equipment comprising: first means, to which a telephone line is to be coupled, for controllably monitoring said line for the presence of communication signals lying within a prescribed plurality of frequency bands and producing respective detection signals in response to the presence of communication signals within respective ones of said frequency bands; second means coupled to said first means, for causing said first means to monitor said line for the presence of communication signals on said line and, upon said first means not having produced a detection signal, generating an output signal for enabling test equipment to seize said line.
Claim 12
Dependent Claim
112 words
An interface circuit for controllably coupling a telephone line to line test equipment comprising: first means, to which a telephone line is to be coupled, for controllably monitoring said line for the presence of communication signals lying within a prescribed plurality of frequency bands and producing respective detection signals in response to the presence of communication signals within respective ones of said frequency bands; second means coupled to said first means, for causing said first means to monitor said line for the presence of communication signals on said line and, upon said first means not having produced a detection signal, generating an output signal for enabling test equipment to seize said line.
Claim 13
Dependent Claim
76 words
An interface circuit according to claim 10, wherein said second means comprises switch means for generating a first enabling signal in response to which said first means is enabled to monitor said line, and gate means, coupled to said first means and responsive to said first enabling signal, for generating said output signal in the absence of the production of a detection signal by said first means, but otherwise preventing the generation of said output signal.
Claim 14
Dependent Claim
32 words
An interface circuit according to claim 11, wherein said second means comprises means for maintaining the generation of said output signal until the line is no longer seized by said test equipment.
Claim 15
Dependent Claim
30 words
An interface circuit according to claim 10, further including third means for controllably coupling said test equipment to said line in response to said second means generating said output signal.
Claim 16
Dependent Claim
42 words
An interface circuit according to claim 13, wherein said second means comprises means for maintaining the generation of said output signal until the line is no longer seized by said test equipment and thereafter controllably decoupling said test equipment from said line.
Claim 17
Dependent Claim
67 words
An interface circuit according to claim 11, further comprising third means for causing said second means to generate said output signal irrespective of the operation of said first means, said third means including second switch means for generating a second enabling signal, and wherein said gate means includes means, responsive to said first and second enabling signals, for causing said second means to generate said output signal.
Claim 18
Independent Claim
95 words
A method of preventing the corruption of communication signals being transmitted over a telephone line in the course of coupling telephone line test equipment to said telephone line comprising the steps of: (a) monitoring said telephone line for the presence of communication signals lying within a prescribed plurality of frequency bands and producing respective detection signals in response to the presence of communication signals within respective ones of said frequency bands; and (b) upon step (a) not having produced a detection signal, generating an output signal for enabling said test equipment to seize said line.
Claim 19
Independent Claim
95 words
A method of preventing the corruption of communication signals being transmitted over a telephone line in the course of coupling telephone line test equipment to said telephone line comprising the steps of: (a) monitoring said telephone line for the presence of communication signals lying within a prescribed plurality of frequency bands and producing respective detection signals in response to the presence of communication signals within respective ones of said frequency bands; and (b) upon step (a) not having produced a detection signal, generating an output signal for enabling said test equipment to seize said line.
Claim 20
Dependent Claim
24 words
A method according to claim 16, wherein step (b) includes controllably coupling said test equipment to said line in response to said output signal.
Claim 21
Dependent Claim
38 words
A method to claim 17, further including the step of (c) maintaining the generation of said output signal until the line is no longer seized by said test equipment and thereafter decoupling said test equipment from said line.
Claim 22
Dependent Claim
90 words
An interface circuit for controllably coupling a telephone line to line test equipment comprising: first means, to which a telephone line is to be coupled, for controllably monitoring a condition of said line representative of the use of said line without seizing said line; and second means, coupled to said first means, for causing said first means to monitor said line for a condition representative of the use of said line and providing an output indicative of whether or not said line may be seized by said line test equipment.
Claim 23
Dependent Claim
90 words
An interface circuit for controllably coupling a telephone line to line test equipment comprising: first means, to which a telephone line is to be coupled, for controllably monitoring a condition of said line representative of the use of said line without seizing said line; and second means, coupled to said first means, for causing said first means to monitor said line for a condition representative of the use of said line and providing an output indicative of whether or not said line may be seized by said line test equipment.
Claim 24
Dependent Claim
35 words
An interface circuit according to claim 19, wherein said first means comprises means for monitoring said line for the presence of communication signals and providing an output in responsive to the presence of communication signals.
Claim 25
Dependent Claim
60 words
An interface circuit according to claim 20, wherein said second means comprises means, coupled to said first means, for causing said first means to monitor said line for the presence of communication signals on said line and, in the absence thereof, generating an output signal in response to which said line test equipment may cause said line to be seized.
Claim 26
Dependent Claim
46 words
An interface circuit according to claim 21, wherein said first means comprises means for monitoring said line for the presence of communication signals in respectively different frequency bands and providing an output in response to the presence of communication signals in any of said frequency bands.
Claim 27
Dependent Claim
82 words
An interface circuit according to claim 22, wherein said second means comprises switch means for generating an enabling signal in response to which said first means is enabled to monitor said line and gate means coupled to receive said enabling signal and the output of said first means and generating said output signal after the generation of said enabling signal by said switch means in the absence of communication signals on said line, but otherwise preventing the generation of said output signal.
Claim 28
Dependent Claim
32 words
An interface circuit according to claim 23, wherein said second means comprises means for maintaining the generation of said output signal until the line is no longer seized by said test equipment.
Claim 29
Dependent Claim
29 words
An interface circuit according to claim 19, further including third means for controllably coupling said test equipment to said line in response to said second means providing said output.
Claim 30
Dependent Claim
38 words
An interface circuit according to claim 25, wherein said second means comprises means for providing said output until the line is no longer seized by said test equipment and thereafter controllably decoupling said test equipment from said line.
Claim 31
Dependent Claim
28 words
An interface circuit according to claim 19, further comprising third means for causing said second means to provide said output irrespective of the operation of said first means.
Claim 32
Dependent Claim
87 words
An interface circuit according to claim 20, wherein said second means comprises first switch means for generating a first enabling signal in response to which said first means is enabled to monitor said line and gate means coupled to receive said first enabling signal and the output of said first means and providing said output after the generation of said first enabling signal by said first switch means in the absence of communication signals on said line, but otherwise normally preventing said output signal from being provided.
Claim 33
Dependent Claim
66 words
An interface circuit according to claim 28, further comprising third means for causing said second means to provide said output irrespective of the operation of said first means, said third means including second switch means for generating a second enabling signal, and within said gate means includes means, responsive to said first and second enabling signals, for causing said second means to generate said output signal.
Claim 34
Independent Claim
57 words
A method of controllably coupling a telephone line to line test equipment comprising the steps of: (a) monitoring, without seizing, said telephone line for the presence of a condition of representative of the use of said line and (b) providing an output indicative of whether or not said line may be seized by said line test equipment.
Claim 35
Independent Claim
57 words
A method of controllably coupling a telephone line to line test equipment comprising the steps of: (a) monitoring, without seizing, said telephone line for the presence of a condition of representative of the use of said line and (b) providing an output indicative of whether or not said line may be seized by said line test equipment.
Claim 36
Dependent Claim
31 words
A method according to claim 30, wherein step (a) comprises monitoring said line for the presence of communication signals and providing an output in response to the presence of communication signals.
Claim 37
Dependent Claim
59 words
A method according to claim 31, wherein step comprises monitoring said line for the presence of communication signals on said line and step (b) comprises, in the absence of step (a) detecting the presence of communication signals on said line, generating an output signal in response to which said line test equipment may cause said lien to be seized.
Claim 38
Dependent Claim
41 words
A method according to claim 32, wherein step comprises monitoring said line for the presence of communication signals in respectively different frequency bands and providing an output in response to the presence of communication signals in any of said frequency bands.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-07-02 | 1994-01-01 | 1994-07-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-07-02 | 1998-01-01 | 1998-07-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-07-02 | 2002-01-01 | 2002-07-03 | $7700.00 | Window Closed / Lapsed |