US3796894A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic switching system
Assignee: Italtel SpA
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Filing: 1972-04-05
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Granted: 1974-03-12
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Expires: 1992-04-05
Abstract
Abstract An electronic switching system, particularly for a base band of video signals, comprises a diode bridge with a signal source and a load connected to respective ends of a main diagonal and a pair of normally blocked switching transistors connected between respective ends of a control diagonal and opposite terminals of a d-c supply. The two switching transistors are of opposite conductivity types and are cascaded to conduct simultaneously upon the application of an unblocking voltage to one of them, thereby causing a biasing current to flow in parallel through two pairs of bridge diodes in their forward direction. In the absence of this biasing current, the control diagonal is virtually shortcircuited by a low-resistance path including either a pair of serially connected ancillary diodes with grounded junction or two ancillary transistors, also of opposite conductivity types, which are cut off in the conductive condition of the switching transistors.
Inventors
- 👤 G Marchetti
- 👤 A Tronconi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 21:55
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/51; H03K17/74; H04; H04N; H04N5/00; H04N5/222; H04N5/262; H04N5/268
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
304 words
An electronic switching system comprising: a rectifier bridge including four diodes in respective bridge arms forming two parallel branches of the same polarity between a first bridge corner and a second bridge corner, said branches consisting each of two bridge arms in series with junctions constituting a third and a fourth bridge corner, said third and fourth corners being respectively connectable to a source of alternating-current signals and to a load; biasing means for said bridge including a direct-current supply with a positive and a negative supply terminal, a first transistor of one conductivity type inserted between one supply terminal and said first corner, and a second transistor of opposite conductivity type inserted between the other supply terminal and said second corner, said transistors being so poled as to pass in their conductive condition a biasing current through said branches in the forward direction of all said diodes; control means for simultaneously reversing the state of conductivity of said first and second transistors, thereby alternately blocking and unblocking the flow of said biasing current, said first transistor having an input electrode connected to said control means and an output electrode connected to an input electrode of said second transistor; and electronic circuit means responsive to said bIasing current for establishing a low-resistance shunt path between said first and second corners in the nonconductive condition of said first and second transistors, said electronic circuit means comprising a third transistor of said one conductivity type inserted between said one supply terminal and said second corner, said third transistor having an input electrode connected to an output electrode of said second transistor, and a fourth transistor of said opposite conductivity type inserted between said other supply terminal and said first corner, said fourth transistor having an input electrode connected to the output electrode of said first transistor.
Claim 2
Dependent Claim
304 words
An electronic switching system comprising: a rectifier bridge including four diodes in respective bridge arms forming two parallel branches of the same polarity between a first bridge corner and a second bridge corner, said branches consisting each of two bridge arms in series with junctions constituting a third and a fourth bridge corner, said third and fourth corners being respectively connectable to a source of alternating-current signals and to a load; biasing means for said bridge including a direct-current supply with a positive and a negative supply terminal, a first transistor of one conductivity type inserted between one supply terminal and said first corner, and a second transistor of opposite conductivity type inserted between the other supply terminal and said second corner, said transistors being so poled as to pass in their conductive condition a biasing current through said branches in the forward direction of all said diodes; control means for simultaneously reversing the state of conductivity of said first and second transistors, thereby alternately blocking and unblocking the flow of said biasing current, said first transistor having an input electrode connected to said control means and an output electrode connected to an input electrode of said second transistor; and electronic circuit means responsive to said bIasing current for establishing a low-resistance shunt path between said first and second corners in the nonconductive condition of said first and second transistors, said electronic circuit means comprising a third transistor of said one conductivity type inserted between said one supply terminal and said second corner, said third transistor having an input electrode connected to an output electrode of said second transistor, and a fourth transistor of said opposite conductivity type inserted between said other supply terminal and said first corner, said fourth transistor having an input electrode connected to the output electrode of said first transistor.
Claim 3
Dependent Claim
110 words
A switching system as defined in claim 1 wherein said first and second transistors each include an emitter connected to the associated supply terminal, a base constituting its input electrode and a collector constituting its output electrode, said biasing means further including a first resistive connection from the base of said first transistor to said one supply terminal, a second resistive connection from the base of said second transistor to said other supply terminal, a first series resistor between the collector of said first transistor and said first corner, and a second series resistor of substantially the same magnitude between the collector of said second transistor and said second corner.
Claim 4
Dependent Claim
21 words
A switching system as defined in claim 2 wherein said first and second transistors are of NPN and PNP type, respectively.
Claim 5
Dependent Claim
44 words
A switching system as defined in claim 1 wherein the connection between said output electrode of said first transistor and said input electrode of said fourth transistors includes two further diodes connected back-to-back and having a junction connected to one of said supply terminals.
Claim 6
Dependent Claim
60 words
A switching system as defined in claim 1 wherein said input electrodes are bases and said output electrodes are collectors, said first and fourth transistors being of NPN type and having each an emitter tied to said negative supply terminal, said second and third transistors being of PNP type and having each an emitter tied to said positive supply terminal.
Claim 7
Dependent Claim
61 words
A switching system as defined in claim 1 wherein said four diodes are poled to pass current from said second corner to said first corner, said first transistor being of NPN type and inserted between said first corner and said negative supply terminal, said second transistor being of PNP type and inserted between said second corner and said positive supply terminal.
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) | 1977-03-11 | 1977-09-10 | 1978-03-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-11 | 1981-09-10 | 1982-03-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-11 | 1985-09-10 | 1986-03-12 | $7700.00 | Window Closed / Lapsed |