US3742151A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Communication call holding and supervising circuit
Assignee: AT&T Inc
•
Filing: 1971-12-20
•
Granted: 1973-06-26
•
Expires: 1991-12-20
Abstract
Abstract An electronic call holding circuit including a PNPN switch and an NPN transistor in a constant current configuration across a telephone line is disclosed. A pair of photoresistive devices isolate the line from logic control circuitry and provide for the coupling of hold commands to the PNPN switch and for the detection of call supervisory signals on the line following the application of a constant current variable impedance hold condition across the line.
Inventors
- 👤 P Ruether
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 01:53
CPC Classifications
H; H04; H04M; H04M9/00; H04M9/002; H04M9/005; H04M9/006
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
156 words
A circuit for holding a call on a communication line comprising a constant current transistor circuit arrangement for applying a controllable electrical impedance across said line to hold a call on said line, a transistor switch responsive to a receipt of a hold request signal for connecting said transistor circuit arrangement to said line for applying said controllable impedance to said line, means electrically biasing said transistor circuit arrangement, said biasing means including a Zener diode and voltage divider network for cooperating with electrical signals on said line for controlling said impedance to regulate a constant magnitude of current flow on said line for call holding, said voltage divider network including a photoresistive device having a Resistor element serially connected with said Zener diode, and means light coupled to said resistor element and being responsive to a receipt of a hold request signal, said Zener diode providing a fixed voltage for biasing said transistor circuit arrangement.
Claim 2
Dependent Claim
156 words
A circuit for holding a call on a communication line comprising a constant current transistor circuit arrangement for applying a controllable electrical impedance across said line to hold a call on said line, a transistor switch responsive to a receipt of a hold request signal for connecting said transistor circuit arrangement to said line for applying said controllable impedance to said line, means electrically biasing said transistor circuit arrangement, said biasing means including a Zener diode and voltage divider network for cooperating with electrical signals on said line for controlling said impedance to regulate a constant magnitude of current flow on said line for call holding, said voltage divider network including a photoresistive device having a Resistor element serially connected with said Zener diode, and means light coupled to said resistor element and being responsive to a receipt of a hold request signal, said Zener diode providing a fixed voltage for biasing said transistor circuit arrangement.
Claim 3
Dependent Claim
49 words
The invention defined in claim 1 further comprising means responsive to a receipt of a call hold initiating signal for activating said light coupled means to alter the resistance of said resistance element for effecting the application of said fixed voltage to bias said constant current transistor circuit arrangement.
Claim 4
Dependent Claim
53 words
The invention defined in claim 2 wherein said activating means includes a bistable flip-flop responsive to a receipt of a call hold initiating signal from a telephone set for supplying an output signal, and, amplifier means responsive to said output signal for applying a hold request signal to activate said light coupled means.
Claim 5
Dependent Claim
23 words
The invention defined in claim 1 wherein said constant current transistor circuit arrangement includes means for sensing call supervisory signals on said line.
Claim 6
Dependent Claim
56 words
The invention defined in claim 4 wherein said sensing means includes a photoresistive device having a resistor element and means light coupled to said element and being responsive to supervisory signals on said line for altering the resistance of said resistor element, and circuitry responsive to said resistance altering for sensing supervisory signals on said line.
Claim 7
Dependent Claim
79 words
The invention defined in claim 5 wherein said supervisory signals include a call disconnect signal, said sensing circuitry includes means responsive to said resistance altering for detecting a call disconnect signal, means controlled by said detecting means for defining a timed interval, and means operated by said defining means at the expiration of said interval for generating an electrical signal to control said transistor switch for effecting a disconnection of said constant current transistor circuit arrangement from said line.
Claim 8
Dependent Claim
61 words
The invention defined in claim 6 wherein said generating means includes a monopulser amplifer operable for generating an electrical pulse signal, said defining means includes a transistor timing circuit activatable for operating said monopulser amplifier, and said detecting means includes a transistor amplifier responsive to a prescribed altering of the resistance of said resistor element for activating said transistor timing circuit.
Claim 9
Dependent Claim
97 words
An electronic call holding circuit for a communication line having first and second conductors and comprising a transistor switch, a transistor arrangement for applying an electrical holding condition across said conductors, a first photoresistive device responsive to a receipt of a hold signal for operating said transistor switch and said transistor arrangement, and a second photoresistive device controlled by said electrical holding condition for detecting call supervisory signals on said line, said transistor arrangement including means including said second photoresistive device for supplying a constant current controllable impedance across said conductors for call holding on said line.
Claim 10
Dependent Claim
97 words
An electronic call holding circuit for a communication line having first and second conductors and comprising a transistor switch, a transistor arrangement for applying an electrical holding condition across said conductors, a first photoresistive device responsive to a receipt of a hold signal for operating said transistor switch and said transistor arrangement, and a second photoresistive device controlled by said electrical holding condition for detecting call supervisory signals on said line, said transistor arrangement including means including said second photoresistive device for supplying a constant current controllable impedance across said conductors for call holding on said line.
Claim 11
Dependent Claim
58 words
The invention defined in claim 8 wherein said second photoresistive device includes a resistor element and lamp means light coupled to said element for altering the resistance of said element, and said supplying means includes a constant current amplifier including a transistor having an emitter electrode serially connected with said lamp means and one of said line conductors.
Claim 12
Dependent Claim
43 words
The invention defined in claim 9 wherein said constant current amplifier transistor includes a base electrode, said amplifier further including a Zener diode and a voltage divider network for supplying a fixed voltage to said base electrode for call holding on said line.
Claim 13
Dependent Claim
62 words
The invention defined in claim 10 wherein said first photoresistive device includes a lamp element respOnsive to a receipt of a hold signal for emitting light signals and a resistor means connected in said voltage divider network and responsive to the emitted light signals for changing its resistance to control said Zener diode to supply said fixed voltage to said base electrode.
Claim 14
Dependent Claim
91 words
The invention defined in claim 11 wherein said constant current amplifier transistor further includes a collector electrode, and said transistor switch includes a PNPN transistor having a cathode electrode connected to said collector electrode, an anode electrode connected to a second one of said line conductors, and a gate electrode connected to said voltage divider network and responsive to a resistance change of said resistor means for activating said PNPN transistor electrically to connect said collector electrode through said cathode and anode electrodes to said second one of said line conductors.
Claim 15
Dependent Claim
42 words
The invention defined in claim 12 further comprising means operable for energizing said lamp element to emit said light signals, and a bistable device responsive to a receipt of a hold initiating signal from a telephone set for operating said energizing means.
Claim 16
Dependent Claim
45 words
The invention defined in claim 13 further comprising means defining a timed interval for a valid call hold removal signal, and an amplifier activated by an alteration of said resistance of said resistor element in response to a call hold removal signal on said line.
Claim 17
Dependent Claim
77 words
The invention defined in claim 14 further comprising means activated by said defining means for generating a reset signal for said bistable device to effect a release of said energizing means and a deactivation of said transistor switch, and said bistable device selectively responsive to a receipt of a reset signal from said generating means and a hold removal signal from said telephone set for controlling said bistable device to effect a release of said energizing means.
Claim 18
Dependent Claim
86 words
An electronic call holding circuit for a communication line having a pair of conductors and comprising a transistor for establishing a hold condition across the conductors, a control arrangement for detecting control signals for applying and removing the hold condition, a semiconductor gate connected in series with said transistor for operating said transistor, and a voltage divider arrangement including a photoresistance light coupled to said control arrangement for operating said semiconductor gate and biasing said transistor to regulate a constant magnitude of current on the line.
Claim 19
Dependent Claim
86 words
An electronic call holding circuit for a communication line having a pair of conductors and comprising a transistor for establishing a hold condition across the conductors, a control arrangement for detecting control signals for applying and removing the hold condition, a semiconductor gate connected in series with said transistor for operating said transistor, and a voltage divider arrangement including a photoresistance light coupled to said control arrangement for operating said semiconductor gate and biasing said transistor to regulate a constant magnitude of current on the line.
Claim 20
Dependent Claim
39 words
An electronic call holding circuit in accordance with claim 16 further comprising a light emitting element in series with said transistor and light coupled to said control arrangement for applying disconnect signals from the line to said control arrangement.
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) | 1976-06-25 | 1976-12-25 | 1977-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-25 | 1980-12-25 | 1981-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-25 | 1984-12-25 | 1985-06-26 | $7700.00 | Window Closed / Lapsed |