US3879579A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic direct access arrangement selector
Assignee: MI 2 Inc
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Filing: 1973-03-21
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Granted: 1975-04-22
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Expires: 1993-03-21
Abstract
Abstract A circuit providing automatic or manual selection of and connection of a data terminal to one of two alternative direct access arrangement terminal units. A four pole double throw relay is actuated by a logic circuit when a ring signal occurs at a first terminal unit or when the first terminal is manually selected to connect the data terminal to the first terminal unit. Otherwise, the relay is not actuated and connects the data terminal to the second terminal unit.
Inventors
- 👤 Richard D Fretwell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 12:42
CPC Classifications
H; H04; H04M; H04M11/00; H04M11/06
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
359 words
A circuit for selecting and alternatively connecting a data terminal to one of two direct access arrangement (DAA) terminal units, said data terminal including a ring detector connected to a first of said DAA units for shifting from a first to a second logic level in response to a ring signal and including an OH circuit for shifting its output from a first to a second logic level when said data terminal is off hook; said circuit comprising: a. a multiple pole, double throw, electrically operated switch means connected to said DAA terminal units and having wiper terminals connected to said data terminal, for connecting said data terminal to a first one of said DAA terminal units when said switch means is actuated and for connecting said data terminal to the other DAA terminal unit when said switch means is not actuated; and b. logic circuit means connected to said switch means and having inputs connected to the output of said ring detector and the output of said off-hook (OH) circuit for actuating said switch means in response to the simultaneous existence of a ring signal at said ring detector and an on hook state and for holding said switch means in an actuated state in response to simultaneous existence of an off hook state and an actuated switch means. c. said logic circuit means further including a first transistor switch having its input connected to said OH circuit for being turned on in response to an off hook state and for being turned off in response to an on hook state; d. a second transistor switch series connected to said first transistor switch and having its input effectively connected to the output of said logic circuit means for being turned on when said switch means is activated; e. a third transistor switch connected parallel to said series connected first and second transistor switches and having its input connected to said ring detector for being turned on in response to a ring state at said ring detector; and f. a diode connecting the input of said third transistor switch to the node intermediate the first and second transistor switches.
Claim 2
Dependent Claim
359 words
A circuit for selecting and alternatively connecting a data terminal to one of two direct access arrangement (DAA) terminal units, said data terminal including a ring detector connected to a first of said DAA units for shifting from a first to a second logic level in response to a ring signal and including an OH circuit for shifting its output from a first to a second logic level when said data terminal is off hook; said circuit comprising: a. a multiple pole, double throw, electrically operated switch means connected to said DAA terminal units and having wiper terminals connected to said data terminal, for connecting said data terminal to a first one of said DAA terminal units when said switch means is actuated and for connecting said data terminal to the other DAA terminal unit when said switch means is not actuated; and b. logic circuit means connected to said switch means and having inputs connected to the output of said ring detector and the output of said off-hook (OH) circuit for actuating said switch means in response to the simultaneous existence of a ring signal at said ring detector and an on hook state and for holding said switch means in an actuated state in response to simultaneous existence of an off hook state and an actuated switch means. c. said logic circuit means further including a first transistor switch having its input connected to said OH circuit for being turned on in response to an off hook state and for being turned off in response to an on hook state; d. a second transistor switch series connected to said first transistor switch and having its input effectively connected to the output of said logic circuit means for being turned on when said switch means is activated; e. a third transistor switch connected parallel to said series connected first and second transistor switches and having its input connected to said ring detector for being turned on in response to a ring state at said ring detector; and f. a diode connecting the input of said third transistor switch to the node intermediate the first and second transistor switches.
Claim 3
Dependent Claim
359 words
A circuit for selecting and alternatively connecting a data terminal to one of two direct access arrangement (DAA) terminal units, said data terminal including a ring detector connected to a first of said DAA units for shifting from a first to a second logic level in response to a ring signal and including an OH circuit for shifting its output from a first to a second logic level when said data terminal is off hook; said circuit comprising: a. a multiple pole, double throw, electrically operated switch means connected to said DAA terminal units and having wiper terminals connected to said data terminal, for connecting said data terminal to a first one of said DAA terminal units when said switch means is actuated and for connecting said data terminal to the other DAA terminal unit when said switch means is not actuated; and b. logic circuit means connected to said switch means and having inputs connected to the output of said ring detector and the output of said off-hook (OH) circuit for actuating said switch means in response to the simultaneous existence of a ring signal at said ring detector and an on hook state and for holding said switch means in an actuated state in response to simultaneous existence of an off hook state and an actuated switch means. c. said logic circuit means further including a first transistor switch having its input connected to said OH circuit for being turned on in response to an off hook state and for being turned off in response to an on hook state; d. a second transistor switch series connected to said first transistor switch and having its input effectively connected to the output of said logic circuit means for being turned on when said switch means is activated; e. a third transistor switch connected parallel to said series connected first and second transistor switches and having its input connected to said ring detector for being turned on in response to a ring state at said ring detector; and f. a diode connecting the input of said third transistor switch to the node intermediate the first and second transistor switches.
Claim 4
Dependent Claim
359 words
A circuit for selecting and alternatively connecting a data terminal to one of two direct access arrangement (DAA) terminal units, said data terminal including a ring detector connected to a first of said DAA units for shifting from a first to a second logic level in response to a ring signal and including an OH circuit for shifting its output from a first to a second logic level when said data terminal is off hook; said circuit comprising: a. a multiple pole, double throw, electrically operated switch means connected to said DAA terminal units and having wiper terminals connected to said data terminal, for connecting said data terminal to a first one of said DAA terminal units when said switch means is actuated and for connecting said data terminal to the other DAA terminal unit when said switch means is not actuated; and b. logic circuit means connected to said switch means and having inputs connected to the output of said ring detector and the output of said off-hook (OH) circuit for actuating said switch means in response to the simultaneous existence of a ring signal at said ring detector and an on hook state and for holding said switch means in an actuated state in response to simultaneous existence of an off hook state and an actuated switch means. c. said logic circuit means further including a first transistor switch having its input connected to said OH circuit for being turned on in response to an off hook state and for being turned off in response to an on hook state; d. a second transistor switch series connected to said first transistor switch and having its input effectively connected to the output of said logic circuit means for being turned on when said switch means is activated; e. a third transistor switch connected parallel to said series connected first and second transistor switches and having its input connected to said ring detector for being turned on in response to a ring state at said ring detector; and f. a diode connecting the input of said third transistor switch to the node intermediate the first and second transistor switches.
Claim 5
Dependent Claim
115 words
A circuit according to claim 1 wherein said logic circuit means comprises: a. a first OR gate having its output effectively connected to said switch means for actuating said switch means; b. a first AND gate having its output connected to an input of said first OR gate and having a pair of inputs, one input connected to the output of said OR gate and the other input connected to said OH circuit; and c. a second AND gate having its output connected to another input of said first or gate, the second AND gate having an inverting input connected to said OH circuit and having a second input effectively connected to said ring detector.
Claim 6
Dependent Claim
69 words
A circuit according to claim 2 wherein a second OR gate is interposed between said second input of said second AND gate and said ring detector and wherein a manual selection switch is connected to another input of said second OR gate for additionally actuating said switch means in response to the simultaneous existence of an on hook state and a manual selection of said first DAA terminal unit.
Claim 7
Dependent Claim
30 words
A circuit according to claim 3 wherein said logic circuit means includes a logic level shifting interface interposed between the output of said first OR gate and said switch means.
Claim 8
Dependent Claim
57 words
A circuit according to claim 1 wherein said logic circuit means comprises logic circuit for generating the Boolean logic function: R . O'' + O . X X where R represents a ring state at the output of said ring detector, O represents an off hook state and X represents the actuated state of said switch means.
Claim 9
Dependent Claim
71 words
A circuit according to claim 1 wherein said logic circuit means comprises a logic circuitry for generating the Boolean logic function: R . O'' + O . X + M.O'' X where R represents a ring state at the output of said ring detector, O represents an off hook state, X represents the actuated state of said switch means and M represents a manual selection of said first DAA terminal unit.
Claim 10
Dependent Claim
55 words
A circuit according to claim 1 wherein said first transistor switch and said third transistor switch are connected to a common ground and wHerein a logic level shifting circuit is interposed between the output of said logic circuit means and the non-grounded end of said parallel third transistor switch and first and second transistor switches.
Claim 11
Dependent Claim
57 words
A circuit according to claim 7 wherein a first diode connects the input of said third transistor switch to said ring detector and a second diode connects the input of said third transistor switch to a manual selection switch for additionally turning on said second switch in response to manual selection of said first DAA terminal unit.
Claim 12
Dependent Claim
81 words
A circuit according to claim 8 wherein a first shunt resistance and capacitance are shunted across the input of said first transistor switch for holding it in a turned on state a selected time delay after the beginning of an on hook state and wherein a second shunt resistance and capacitance are shunted across the input of said third transistor switch for holding it on for a selected time period after the end of a ring state at said ring detector.
References Cited (Backward Citations)
US3193620A
Cited
US3649759A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-21 | 1978-10-21 | 1979-04-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-21 | 1982-10-21 | 1983-04-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-21 | 1986-10-21 | 1987-04-22 | $7700.00 | Window Closed / Lapsed |