US3622699A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Facsimile system with preemphasis varied by signal rate
Assignee: Philips North America LLC
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Filing: 1969-05-16
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Granted: 1971-11-23
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Expires: 1989-05-16
Abstract
Abstract An improved facsimile system capable of either yielding improved quality copy at the prior art transmission speed or of yielding copy of quality comparable to the prior art machine in a reduced period of transmission time is disclosed. These improvement result from a modified gray-scale signal circuit at the transmitter which has its gray-scale transfer function-time dependent along with an improved receiver circuit which has a gray-scale time-dependent transfer function. These modifications cause both transmitter and receiver to tend to saturate at lower signal levels for rapidly changing gray-scale inputs.
Inventors
- 👤 William E Richeson Jr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 03:02
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/407; H04N7/00; H04N7/12
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
97 words
The method of improving the performance of a facsimile transmission system comprising the steps of: increasing the amount of regenerative feedback in the receiver for more rapidly changing baseband signals so that the point of receiver saturation decreases as the rate of change of baseband signals increases; and increasing the gain of a modified Schmitt trigger circuit in the transmitter in response to an increase in baseband rate of change so that the input to a voltage-controlled oscillator reaches its maximum value at lower Schmitt trigger input levels for higher rates of changes in the signal level.
Claim 2
Independent Claim
97 words
The method of improving the performance of a facsimile transmission system comprising the steps of: increasing the amount of regenerative feedback in the receiver for more rapidly changing baseband signals so that the point of receiver saturation decreases as the rate of change of baseband signals increases; and increasing the gain of a modified Schmitt trigger circuit in the transmitter in response to an increase in baseband rate of change so that the input to a voltage-controlled oscillator reaches its maximum value at lower Schmitt trigger input levels for higher rates of changes in the signal level.
Claim 3
Dependent Claim
51 words
The method of claim 1 wherein the step of increasing the gain comprises the steps of: lowering the input attenuation of the modified Schmitt trigger circuit and lowering the impedance between stages of the modified Schmitt trigger circuit, both in response to an increase in the signal level rate of change.
Claim 4
Dependent Claim
131 words
In a facsimile system comprising a transmitter and a receiver, the improvement comprising: a modified Schmitt trigger circuit in the transmitter having first and second current control devices therein; preemphasis means in said modified Schmitt trigger circuit for improving the rapid response characteristics of said transmitter, said preemphasis means comprising a series inductor capacitor circuit in parallel with a resistance coupling the output of said first current control device to the input of said second current control device, and a parallel resistor capacitor circuit for providing an input impedance to said first current control device which decreases as the rapidity of the input signals increases; and postemphasis means in the receiver for improving the rapid response characteristics of said receiver comprising a series capacitor-inductor circuit across the output of said receiver.
Claim 5
Dependent Claim
131 words
In a facsimile system comprising a transmitter and a receiver, the improvement comprising: a modified Schmitt trigger circuit in the transmitter having first and second current control devices therein; preemphasis means in said modified Schmitt trigger circuit for improving the rapid response characteristics of said transmitter, said preemphasis means comprising a series inductor capacitor circuit in parallel with a resistance coupling the output of said first current control device to the input of said second current control device, and a parallel resistor capacitor circuit for providing an input impedance to said first current control device which decreases as the rapidity of the input signals increases; and postemphasis means in the receiver for improving the rapid response characteristics of said receiver comprising a series capacitor-inductor circuit across the output of said receiver.
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) | 1974-11-22 | 1975-05-24 | 1975-11-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-22 | 1979-05-24 | 1979-11-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-22 | 1983-05-24 | 1983-11-23 | $7700.00 | Window Closed / Lapsed |