US3582788A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Telecommunication system with automatic volume control
Assignee: Italtel SpA
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Filing: 1968-04-29
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Granted: 1971-06-01
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Expires: 1988-04-29
Abstract
Abstract Multichannel telephone system with transmission of pilot frequency to control the gain of an amplifier at a remote terminal by comparison of a reference voltage with a control voltage proportional to pilot amplitude, the pilot frequency being switchable between zero and a relatively low normal amplitude level for signaling in the absence of voice-frequency transmission and between this low level and an abnormally high level for signaling during such transmission; the changeover from normal to abnormal level triggers a compensating circuit which reduces the control voltage at the comparator input or increases the magnitude of the reference voltage to maintain the gain control independent of the pilot level.
Inventors
- 👤 Francesco Castagna
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 09:16
CPC Classifications
H; H04; H04J; H04J1/00; H04J1/02; H04J1/14
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
258 words
In a telecommunication system having a first terminal, a second terminal, a transmission channel linking said terminals, means at said first terminal for modulating a carrier with message signals to be transmitted over said channel within a predetermined frequency band, means including a variable-gain amplifier at said second terminal for demodulating said carrier to reconstitute said message signals, oscillator means at said first terminal for generating a constant-frequency pilot oscillation within said band for transmission over said channel, and volume-control means at said second terminal including a control element in said channel for regulating the effective output of said amplifier in response to variations in the amplitude of the incoming pilot oscillation, the combination therewith of: signaling means at said first terminal connected to vary the output of said oscillator means between a normal level and an abnormal level, the difference between said levels exceeding the range of amplitude variations from said normal level to be offset by said volume-control means; switch means at said second terminal connected to said channel at a point beyond said element and responsive to changes in said incoming pilot oscillation from a first amplitude range corresponding to said normal level to a second amplitude range corresponding to said abnormal level; signal-repeating means at said second terminal controlled by said switch means; and compensating means at said second terminal controlled by said switch means for readjusting said volume-control means to respond in substantially identical manner to amplitude excursions of said pilot oscillation with reference to the mean of either of said amplitude ranges.
Claim 2
Dependent Claim
258 words
In a telecommunication system having a first terminal, a second terminal, a transmission channel linking said terminals, means at said first terminal for modulating a carrier with message signals to be transmitted over said channel within a predetermined frequency band, means including a variable-gain amplifier at said second terminal for demodulating said carrier to reconstitute said message signals, oscillator means at said first terminal for generating a constant-frequency pilot oscillation within said band for transmission over said channel, and volume-control means at said second terminal including a control element in said channel for regulating the effective output of said amplifier in response to variations in the amplitude of the incoming pilot oscillation, the combination therewith of: signaling means at said first terminal connected to vary the output of said oscillator means between a normal level and an abnormal level, the difference between said levels exceeding the range of amplitude variations from said normal level to be offset by said volume-control means; switch means at said second terminal connected to said channel at a point beyond said element and responsive to changes in said incoming pilot oscillation from a first amplitude range corresponding to said normal level to a second amplitude range corresponding to said abnormal level; signal-repeating means at said second terminal controlled by said switch means; and compensating means at said second terminal controlled by said switch means for readjusting said volume-control means to respond in substantially identical manner to amplitude excursions of said pilot oscillation with reference to the mean of either of said amplitude ranges.
Claim 3
Dependent Claim
75 words
The combination defined in claim 1 wherein said volume-control means comprises detector means for deriving a unipolar control voltage from the amplitude of said incoming pilot oscillation, a source of constant reference voltage, and comparison means having two inputs connected to receive said control voltage and said reference voltage, respectively; said compensating means including an impedance network in series with one of said inputs and switchover means for modifying the effective impedance of said network.
Claim 4
Dependent Claim
29 words
The combination defined in claim 2 wherein said network includes a voltage divider, said switchover means being connected across a section of said voltage divider for optionally short-circuiting same.
Claim 5
Dependent Claim
35 words
The combination defined in claim 2 wherein said network includes a voltage divider with a pair of parallel branches, said switchover means being connected in series with one of said branches for optionally open-circuiting same.
Claim 6
Dependent Claim
26 words
The combination defined in claim 2 wherein said switchover means comprises a relay and voltage-sensitive trigger means connected to said detector means for operating said relay.
Claim 7
Dependent Claim
20 words
The combination defined in claim 5 wherein said relay is provided with an armature forming part of said switch means.
Claim 8
Dependent Claim
30 words
The combination defined in claim 2 wherein said switchover means comprises a first transistor and a normally cutoff second transistor connected to be driven to saturation by said first transistor.
Claim 9
Dependent Claim
22 words
The combination defined in claim 2 wherein said compensating means comprises a direct-current amplifier provided with an output circuit including said network.
Claim 10
Dependent Claim
28 words
The combination defined in claim 2 wherein said source of reference voltage includes a Zener diode, said network being connected at least in part across said Zener diode.
Claim 11
Dependent Claim
77 words
The combination defined in claim 1 wherein said abnormal level is higher than said normal level, said signaling means being effective in a busy condition of said channel, further comprising other signaling means at said first terminal effective in an idle condition of said channel for selectively interrupting said pilot frequency and other switch means at said second terminal responsive to interruption of said pilot frequency for carrying out switching operations indicated by said other signaling means.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-05-31 | 1974-11-30 | 1975-06-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-31 | 1978-11-30 | 1979-06-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-31 | 1982-11-30 | 1983-06-01 | $7700.00 | Window Closed / Lapsed |