US4161633A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Subscriber line/trunk circuit
Assignee: Nokia of America Corp
•
Filing: 1978-05-08
•
Granted: 1979-07-17
•
Expires: 1998-05-08
Abstract
Abstract A microprocessor controlled subscriber line circuit for interfacing analog telephone lines and trunks to a digital switching system is disclosed. All processing of incoming analog signals is accomplished by the line circuit, including the interface between the line and a digital switching matrix, measuring, monitoring, testing of the signals associated with the speech path. Additionally, the dc signal powering the carbon microphone on the handset is generated as well as ringing and other tones. Equalization and providing the two-wire to four-wire conversion with acceptable echo performance and minimized cross-office transmission loss are also accomplished. Analog-to-digital and digital-to-analog conversions are accomplished under microprocessor control as are the tone and power generation functions in a programmable power supply configuration utilizing pulse duration modulated feedback control in a programmable signal generator. The described subscriber circuit is particularly advantageous in that it is designed to maximize its implementation using solid state circuit techniques including large scale integration as opposed to conventional components and relays.
Inventors
- 👤 Robert Treiber
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:11
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/005; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H04Q; H04Q1/00; H04Q1/18; H04Q1/56
Claims Analysis
Total Claims: 41
Claim 1
Independent Claim
125 words
A line circuit for providing an interface between at least a subscriber line carrying bidirectional analog communication signals and a digital circuit, said line circuit being subject to undesired line signal return from a two-wire to four-wire conversion means provided therein, comprising: analog-to-digital coder means for converting said analog communication signals to digital signals; digital signal processing means for selectively attenuating said digital signals coupled thereto from said analog-to-digital coder and for subtracting from said attenuated digital signals said undesired line signal return present in said line circuit to provide a composite digital output signal representative of said analog communication signals substantially without the presence therein of said undesired line signal return; and means for coupling said composite digital output signal to said digital circuit.
Claim 2
Dependent Claim
125 words
A line circuit for providing an interface between at least a subscriber line carrying bidirectional analog communication signals and a digital circuit, said line circuit being subject to undesired line signal return from a two-wire to four-wire conversion means provided therein, comprising: analog-to-digital coder means for converting said analog communication signals to digital signals; digital signal processing means for selectively attenuating said digital signals coupled thereto from said analog-to-digital coder and for subtracting from said attenuated digital signals said undesired line signal return present in said line circuit to provide a composite digital output signal representative of said analog communication signals substantially without the presence therein of said undesired line signal return; and means for coupling said composite digital output signal to said digital circuit.
Claim 3
Dependent Claim
57 words
A circuit in accordance with claim 1, further comprising: digital-to-analog converter means for converting return digital communication signals from said digital circuit to return analog communication signals; means for coupling said return digital signals to said signal processing means; and summing means for coupling said return analog communications signals from said digital-to-analog converter to said subscriber line.
Claim 4
Dependent Claim
17 words
A circuit in accordance with claim 2, wherein said analog communication signals include modulation representative of speech.
Claim 5
Dependent Claim
15 words
A circuit in accordance with claim 2, wherein said digital circuit comprises a switching matrix.
Claim 6
Dependent Claim
20 words
A circuit in accordance with claim 2, wherein said analog-to-digital converter includes means for deriving pulse code modulated digital signals.
Claim 7
Dependent Claim
29 words
A circuit in accordance with claim 2, wherein said subscriber line comprises a two-wire telephone line and wherein said means for selctively attenuating said digital signals includes equalizing means.
Claim 8
Dependent Claim
59 words
A circuit in accordance with claim 2, wherein said signal processing means comprises a programmable microcomputer, including: means for sensing subscriber line transmission conditions; and means for coupling signals representative of said sensed subscriber line transmission conditions to said microcomputer to derive control signals for varying the effective line matching impedance in accordance with said sensed subscriber line conditions.
Claim 9
Dependent Claim
87 words
A circuit in accordance with claim 7, wherein said signal processing means further includes: first digital filter means for selectively attenuating said digital signals in accordance with the transfer function of said digital signals including said undesired signal return; second digital filter means for deriving a negative representation of said undesired signal return in accordance with the transfer function of said return signal thru said filter; and means for summing said digital signals and said return signals in accordance with said first and second digital filter means.
Claim 10
Dependent Claim
25 words
A circuit in accordance with claim 8, wherein said first digital filter means provides compensation for transmission line parameters under control of said programmable microcomputer.
Claim 11
Dependent Claim
19 words
A circuit in accordance with claim 8, wherein said first digital filter means includes means for detecting ac signalling.
Claim 12
Dependent Claim
17 words
A circuit in accordance with claim 4, wherein said line circuit is remote from said switching matrix.
Claim 13
Dependent Claim
15 words
A circuit in accordance with claim 7, wherein said microcomputer includes a stored program control.
Claim 14
Dependent Claim
24 words
A circuit in accordance with claim 7, wherein said subscriber line carrying analog communication signals further carries ac voltages indicative of telephone signalling information.
Claim 15
Dependent Claim
35 words
A circuit in accordance with claim 13, further comprising: programmable signal generator means responsive to microcomputer generated control signals for deriving said ac voltages indicative of said telephone signalling information and for deriving dc voltages.
Claim 16
Dependent Claim
62 words
A circuit in accordance with claim 14, further comprising: pulse duration modulated means responsive to said control signals, said control signals being pulse duration modulated signals; transformer means for coupling said pulse duration modulated signals to said programmable signal generator; and means for varying the output of said programmable signal generator in accordance with said pulse duration modulated control signals coupled thereto.
Claim 17
Dependent Claim
23 words
A circuit in accordance with claim 15, wherein one of said signalling voltages generated by said programmable signal generator is a ringing voltage.
Claim 18
Dependent Claim
18 words
A circuit in accordance with claim 15, wherein said sensing means includes means for sensing hook status conditions.
Claim 19
Dependent Claim
17 words
A circuit in accordance with claim 15, wherein said sensing means includes means for sensing ring-trip conditions.
Claim 20
Dependent Claim
18 words
A circuit in accordance with claim 15, wherein said sensing means includes means for sensing dc current changes.
Claim 21
Dependent Claim
17 words
A circuit in accordance with claim 17, wherein said sensing means includes means for sensing dial pulsing.
Claim 22
Dependent Claim
132 words
In a telephone subscriber line circuit, a programmable signal generator for generating an electrically isolated output voltage comprising: means for coupling generated programmably regulated analog voltages to a two-wire line having signals representative of speech modulation thereon; analog-to-digital converter means coupled to said line for sensing said analog voltages and for deriving an electrically isolated digital output signal; signal processing means responsive to said digital output signal for comparing said digital output signal with a reference signal and for deriving a pulse duration modulated feedback control signal in response to said comparing; and regulator means coupled to said two-wire line for controlling said pulse duration modulated feedback control signal to regulate said coupled programmably regulated analog voltages on said two-wire line, said regulator means further including means for generating said analog voltages.
Claim 23
Dependent Claim
132 words
In a telephone subscriber line circuit, a programmable signal generator for generating an electrically isolated output voltage comprising: means for coupling generated programmably regulated analog voltages to a two-wire line having signals representative of speech modulation thereon; analog-to-digital converter means coupled to said line for sensing said analog voltages and for deriving an electrically isolated digital output signal; signal processing means responsive to said digital output signal for comparing said digital output signal with a reference signal and for deriving a pulse duration modulated feedback control signal in response to said comparing; and regulator means coupled to said two-wire line for controlling said pulse duration modulated feedback control signal to regulate said coupled programmably regulated analog voltages on said two-wire line, said regulator means further including means for generating said analog voltages.
Claim 24
Dependent Claim
33 words
In a telephone subscriber circuit in accordance with claim 21, a programmable signal generator for generating an electrically isolated output voltage wherein said analog voltages on said two-wire line include ac signalling voltages.
Claim 25
Dependent Claim
29 words
In a telephone subscriber circuit in accordance with claim 21, a programmable signal generator for generating an electrically isolated output voltage wherein said signal processing means comprises a microcomputer.
Claim 26
Dependent Claim
95 words
In a telephone subscriber circuit in accordance with claim 23, programmable signal generator for generating an electrically isolated output voltage wherein said regulator means includes: switching circuit means having a duty cycle controlled by said feedback control signal and having a switched output signal; and transformer means for transferring energy from the primary thereof to the secondary thereof in response to said switched output signal from said switching circuit such that the amount of energy transferred from said primary to said secondary of said transformer is proportional to the duty cycle of said switching circuit.
Claim 27
Dependent Claim
27 words
In a telephone subscriber circuit in accordance with claim 24, further comprising: means for testing said two-wire line with test voltages generated by said programmable signal generator.
Claim 28
Dependent Claim
39 words
In a telephone subscriber circuit in accordance with claim 24, wherein said regulator means further includes: signal isolation means for isolating the secondary of said transformer from said two-wire line, and wherein said switching circuit is a switching transistor.
Claim 29
Dependent Claim
27 words
In a telephone subscriber circuit in accordance with claim 24, wherein said transformer is a ferrite transformer and wherein said isolation means includes a floating bridge circuit.
Claim 30
Dependent Claim
37 words
In a telephone subscriber circuit in accordance with claim 27, wherein said floating bridge circuit is comprised of a plurality of switches controlled by said microcomputer for generating an output ac voltage from said regulated analog voltage.
Claim 31
Independent Claim
122 words
A method for interfacing at least a subscriber line carrying bidirectional analog communication signals with a digital circuit through a line circuit said line circuit being subject to undesired line signal return from a two-wire to four-wire conversion means provided therein, comprising the steps of: converting said analog communication signals to digital signals; digitally processing said digital signals with a signal processing means by selectively attenuating said digital signals and by subtracting from said attenuated digital signals said undesired line signal return present in said line circuit to provide a composite digital output signal representative of said analog communication signals substantially without the presence therein of said undesired line signal return; and coupling said composite digital output signal to said digital circuit.
Claim 32
Independent Claim
122 words
A method for interfacing at least a subscriber line carrying bidirectional analog communication signals with a digital circuit through a line circuit said line circuit being subject to undesired line signal return from a two-wire to four-wire conversion means provided therein, comprising the steps of: converting said analog communication signals to digital signals; digitally processing said digital signals with a signal processing means by selectively attenuating said digital signals and by subtracting from said attenuated digital signals said undesired line signal return present in said line circuit to provide a composite digital output signal representative of said analog communication signals substantially without the presence therein of said undesired line signal return; and coupling said composite digital output signal to said digital circuit.
Claim 33
Dependent Claim
54 words
A method in accordance with claim 29, further comprising the steps of: converting return digital signals from said digital circuit to return analog communication signals; coupling said return digital signals to said processing means; and coupling said return analog communication signals from said digital-to-analog converter to a said subscriber line thru a summing means.
Claim 34
Dependent Claim
40 words
A method in accordance with claim 30, wherein said subscriber line comprises a two-wire telephone line and wherein said selective attenuation and substraction step includes processing said digital signals for providing digital signal isolation for a two-wire to four-wire conversion.
Claim 35
Dependent Claim
35 words
A method in accordance with claim 30, wherein said signal processing step includes: sensing subscriber line transmission conditions; and varying the selective attenuation of said digital signals in accordance with said sensed subscriber line conditions.
Claim 36
Dependent Claim
74 words
A method in accordance with claim 32 wherein said signal processing step further includes: digitally filtering said digital signals and undesired return signals in accordance with the transfer function of said digital signals and undesired return signals thru said line circuit; deriving a signal representative of said undesired communication signals in accordance with the transfer function of said signals alone; and summing said digital signals and undesired return signals in accordance with transfer functions.
Claim 37
Independent Claim
119 words
A method of providing a programmable signal generator for a bidirectional telephone subscriber line circuit comprising the steps of: coupling generated and programmably regulated analog voltages to a two-wire line; sensing said analog voltages with an analog to digital converter coupled to said line for deriving an electrically isolated digital output signal; comparing said digital output signal with a reference signal in a signal processor responsive to said digital output signal for deriving a pulse duration modulated feedback control signal in response to said comparing; and regulating said programmably regulated analog voltages on said two-wire line with a regulator coupled to said two-wire line for controlling said pulse duration modulated feedback control signal and for generating said analog voltages.
Claim 38
Independent Claim
119 words
A method of providing a programmable signal generator for a bidirectional telephone subscriber line circuit comprising the steps of: coupling generated and programmably regulated analog voltages to a two-wire line; sensing said analog voltages with an analog to digital converter coupled to said line for deriving an electrically isolated digital output signal; comparing said digital output signal with a reference signal in a signal processor responsive to said digital output signal for deriving a pulse duration modulated feedback control signal in response to said comparing; and regulating said programmably regulated analog voltages on said two-wire line with a regulator coupled to said two-wire line for controlling said pulse duration modulated feedback control signal and for generating said analog voltages.
Claim 39
Dependent Claim
98 words
A method in accordance with claim 34, wherein said regulating step includes generating an electrically isolated, regulated output voltage in accordance with the following substeps: switching a solid state circuit having a duty cycle controlled by said feedback control signal and having a switched output signal; and tranferring energy from the primary of a transformer to the secondary thereof in response to said switched output signal from said switching solid state circuit such that the amount of energy transferred from said primary to said secondary of said transformer is proportional to the duty cycle of said switching circuit.
Claim 40
Dependent Claim
22 words
A method in accordance with claim 35 further including the step of: isolating the secondary of said transformer from said two-wire line.
Claim 41
Dependent Claim
25 words
A method in accordance with claim 34 including the further step of testing said two-wire line with test voltages generated by said programmable signal generator.
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) | 1982-07-16 | 1983-01-15 | 1983-07-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-07-16 | 1987-01-15 | 1987-07-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-07-16 | 1991-01-15 | 1991-07-17 | $7700.00 | Window Closed / Lapsed |