US5394465A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Parallel phone detection circuit
Assignee: STMicroelectronics Pte Ltd
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Filing: 1993-01-28
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Granted: 1995-02-28
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Expires: 2013-01-28
Abstract
Abstract A parallel phone detection circuit is described, the function of which is to enable a phone call to be transferred from a first telephone set to a second telephone set. The detection circuit maintains the first telephone set connected to the telephone line until the handset of the second telephone set has been taken off-hook, and then disconnects the first telephone set. The circuit operates by detecting the line current from the telephone line and produces the reference value for comparison purposes related to that line current.
Inventors
- 👤 Sung J. Jo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 11:07
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/80; H04M3/00; H04M3/22; H04M3/2272; H04M3/42; H04M3/428; H04M3/4283
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
128 words
A line current detection circuit for use in a telephone set comprising: means for deriving a comparison current from the line current of a telephone line; generating means for producing sequentially different values of reference currents; means for determining when the value of a reference current generated by the generating means corresponds to the value of the comparison current; means for storing the value of said reference current corresponding to said comparison current so that said reference current is used as a basis for subsequent comparison with said comparison current; and means for subsequently comparing said stored reference current or a current based thereon with said comparison current and for producing an output signal for controlling disconnection of the telephone set to the telephone line in response thereto.
Claim 2
Dependent Claim
128 words
A line current detection circuit for use in a telephone set comprising: means for deriving a comparison current from the line current of a telephone line; generating means for producing sequentially different values of reference currents; means for determining when the value of a reference current generated by the generating means corresponds to the value of the comparison current; means for storing the value of said reference current corresponding to said comparison current so that said reference current is used as a basis for subsequent comparison with said comparison current; and means for subsequently comparing said stored reference current or a current based thereon with said comparison current and for producing an output signal for controlling disconnection of the telephone set to the telephone line in response thereto.
Claim 3
Dependent Claim
37 words
A circuit as claimed in claim 1 further comprising means for reducing said stored reference current by a predetermined offset value, said offset-reduced reference current being used as a basis for subsequent comparison with said comparison current.
Claim 4
Dependent Claim
49 words
A circuit as claimed in claim 1 or 2 which comprises a duration counter connected to receive the output signal from the comparing means, the duration counter being operable to detect whether or not the output signal from the comparing means maintains the same state during a predetermined duration.
Claim 5
Dependent Claim
52 words
A circuit as claimed in claim 1 or 2 comprising connection control means responsive to said output signal for maintaining the telephone set connected to the telephone line until the comparing means detects that a second telephone set has been connected to the telephone line, whereupon the first-mentioned telephone set is disconnected.
Claim 6
Dependent Claim
67 words
A circuit as claimed in claim 4, which comprises a maximum time counter operable to provide an output signal a predetermined time after the first-mentioned telephone set has been placed in an on-hook condition and to control said connection control means to disconnect said first-mentioned telephone set in the condition that a second telephone set has not been connected to the telephone line within said predetermined time.
Claim 7
Dependent Claim
92 words
A circuit as claimed in claim 1 or 2, which comprises: a duration counter connected to receive the output signal from the comparing means, the duration counter being operable to detect whether or not the output signal from the comparing means maintains the same state during a predetermined duration; and connection control means responsive to said output signal for maintaining the telephone set connected to the telephone line until the comparing means detects that a second telephone set has been connected to the telephone line, whereupon the first mentioned set is disconnected.
Claim 8
Dependent Claim
67 words
A circuit as claimed in claim 6, which comprises a maximum time counter operable to provide an output signal a predetermined time after the first-mentioned telephone set has been placed in an on-hook condition and to control said connection control means to disconnect said first-mentioned telephone set in the condition that a second telephone set has not been connected to the telephone line within said predetermined time.
Claim 9
Dependent Claim
40 words
A circuit as claimed in claim 1 or 2 wherein said determining means and said comparing means are provided by a comparator having a first input for receiving said comparison current and a second input for receiving said reference current.
Claim 10
Dependent Claim
23 words
A circuit as claimed in claim 1 or 2 wherein said generating means is operable to produce sequentially successively reduced values of current.
Claim 11
Dependent Claim
21 words
A circuit as claimed in claim 8 wherein said generating means is operable to produce sequentially successively reduced values of current.
Claim 12
Dependent Claim
55 words
A circuit as claimed in claim 9 wherein said generating means comprises a current source, a divider for producing from said current source a plurality of reference currents of different values and switching circuitry for connecting or disconnecting said reference currents of different values thereby to produce said sequentially successively reduced values of reference currents.
Claim 13
Dependent Claim
55 words
A circuit as claimed in claim 10 wherein said generating means comprises a current source, a divider for producing from said current source a plurality of reference currents of different values and switching circuitry for connecting or disconnecting said reference currents of different values thereby to produce said sequentially successively reduced values of reference currents.
Claim 14
Independent Claim
105 words
A method of detecting a telephone line current comprising the steps of: deriving a comparison current from the line current of the telephone line; producing sequentially different values of reference current; determining when the value of a reference current corresponds to the value of the comparison current; storing the value of said reference current corresponding to said comparison current so that said reference current is used as a basis for subsequent comparison with said comparison current; and comparing said stored reference current or a current based thereon with said comparison current and controlling disconnection of a telephone set to a telephone line in response thereto.
Claim 15
Independent Claim
105 words
A method of detecting a telephone line current comprising the steps of: deriving a comparison current from the line current of the telephone line; producing sequentially different values of reference current; determining when the value of a reference current corresponds to the value of the comparison current; storing the value of said reference current corresponding to said comparison current so that said reference current is used as a basis for subsequent comparison with said comparison current; and comparing said stored reference current or a current based thereon with said comparison current and controlling disconnection of a telephone set to a telephone line in response thereto.
Claim 16
Dependent Claim
30 words
A method as claimed in claim 13 further comprising the step of detecting whether or not the output from the comparing means maintains the same state during a predetermined duration.
Claim 17
Dependent Claim
56 words
A method as claimed in claim 13 or 14 further comprising the step of determining whether a second telephone set has been taken off-hook within a predetermined time of a first telephone set being placed in an on-hook condition, and for disconnecting the first telephone set after said predetermined time if such on-hook condition is detected.
Claim 18
Dependent Claim
25 words
A method as claimed in claim 13 or 14 wherein said different values of reference current are produced sequentially as successively reduced values of current.
Claim 19
Dependent Claim
23 words
A method as claimed in claim 15 wherein said different values of reference current are produced sequentially as successively reduced values of current.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-02-27 | 1998-08-29 | 1999-02-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-02-27 | 2002-08-29 | 2003-02-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-02-27 | 2006-08-29 | 2007-02-28 | $7700.00 | Window Closed / Lapsed |