US3987254A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Transformerless amplification circuitry for telecommunication system
Assignee: Italtel SpA
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Filing: 1975-03-20
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Granted: 1976-10-19
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Expires: 1995-03-20
Abstract
Abstract A two-wire line is connected via a resistive hybrid circuit to a high-impedance output of a transmitter amplifier, carrying outgoing voice signals originating at a microphone, and to a high-impedance input of a receiver amplifier, carrying incoming voice signals destined for an earphone. A biasing network, connected across the line in parallel with the hybrid circuit, includes a pair of cascaded complementary transistors whose collectors are interconnected through a low-ohmic voltage divider supplying operating voltage, balanced with reference to the line voltage, to the transmitter ampllifier and delivering a similarly balanced reference voltage to the receiver amplifier.
Inventors
- 👤 Roberto Pipitone
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 11:44
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/60; H04M1/6025
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
133 words
In a telecommunication system, in combination: a two-wire line connected to a source of d-c biasing voltage; a biasing network connected across said line; a signal-transmitting network including first amplifier means with a high-impedance output circuit; a signal-receiving network including second amplifier means with a high-impedance input circuit and with a supply circuit connected across said line; first conductor means connecting said biasing network to said first amplifier means for supplying thereto an operating voltage substantially balanced with respect to the line voltage; second conductor means connecting said biasing network to said second amplifier means for supplying thereto a reference voltage substantially balanced with respect to the line voltage; and a coupling circuit connected across said line and provided with mutually conjugate pairs of terminals respectively connected across said input and output circuits.
Claim 2
Dependent Claim
133 words
In a telecommunication system, in combination: a two-wire line connected to a source of d-c biasing voltage; a biasing network connected across said line; a signal-transmitting network including first amplifier means with a high-impedance output circuit; a signal-receiving network including second amplifier means with a high-impedance input circuit and with a supply circuit connected across said line; first conductor means connecting said biasing network to said first amplifier means for supplying thereto an operating voltage substantially balanced with respect to the line voltage; second conductor means connecting said biasing network to said second amplifier means for supplying thereto a reference voltage substantially balanced with respect to the line voltage; and a coupling circuit connected across said line and provided with mutually conjugate pairs of terminals respectively connected across said input and output circuits.
Claim 3
Dependent Claim
33 words
The combination defined in claim 1 wherein said first amplifier means comprises a transistor stage with supply terminals connected by said first conductor means across a low-resistance intermediate section of said biasing network.
Claim 4
Dependent Claim
22 words
The combination defined in claim 2 wherein said signal-transmitting network comprises a piezoelectric microphone connected across an input of said transistor stage.
Claim 5
Dependent Claim
53 words
The combination defined in claim 2 wherein said coupling network comprises a resistance bridge with two opposite high-resistance arms and two opposite low-resistance arms forming a first diagonal connected across said line and a second diagonal connected across a matching impedance, said low-resistance arms having their midpoints connected across said high-impedance output circuit.
Claim 6
Dependent Claim
29 words
The combination defined in claim 4 wherein said high-impedance output circuit comprises a pair of complementary transistors controlled by said transistor stage and connected in cascade between said midpoints.
Claim 7
Dependent Claim
29 words
The combination defined in claim 1 wherein said second amplifier means comprises a differential-amplifier stage with a supply circuit including a control transistor connected to said second conductor means.
Claim 8
Dependent Claim
22 words
The combination defined in claim 6 wherein said signal-receiving network comprises a piezoelectric earphone connected across an output of said differential-amplifier stage.
Claim 9
Dependent Claim
53 words
The combination defined in claim 6 wherein said coupling network comprises a resistance bridge with two opposite high-resistance arms and two opposite low-resistance arms forming a first diagonal connected across said line and a second diagonal connected across a matching impedance, said high-resistance arms having their midpoints connected across said high-impedance input circuit.
Claim 10
Dependent Claim
29 words
The combination defined in claim 8 wherein said high-impedance input circuit comprises a pair of differentially interconnected transistors in series with a common transistor driven by said control transistor.
Claim 11
Dependent Claim
37 words
The combination defined in claim 1 wherein said biasing network comprises a pair of cascaded complementary transistors with collectors interconnected through a low-ohmic voltage divider, said first and second conductor means being connected to said voltage divider.
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) | 1979-10-19 | 1980-04-19 | 1980-10-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-10-19 | 1984-04-19 | 1984-10-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-10-19 | 1988-04-19 | 1988-10-19 | $7700.00 | Window Closed / Lapsed |