US3838208A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Circuit for reducing white balance variations
Assignee: Panasonic Holdings Corp
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Filing: 1972-12-27
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Granted: 1974-09-24
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Expires: 1992-12-27
Abstract
Abstract A color television receiver having a generator for generating a reference signal by means of ringing for applying this reference signal to a demodulator for the demodulation of a chrominance signal. In the receiver, an oscillator oscillating substantially at a frequency of 3.58 MHz is provided so as to apply its output to the demodulator during reception of a monochromatic television signal, thereby preventing undesirable variations of the white balance depending on the reception of a color television signal or monochromatic television signal irrespective of fluctuations of the characteristics of elements constituting the demodulator.
Inventors
- 👤 Y Fujiwara
- 👤 N Meki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 20:45
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/64; H04N9/73
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
293 words
Circuitry for preventing white balance variations arising when switching from monochromatic television reception to color television reception and vice versa in a television receiver utilizing a reference signal generator of the ringing type, said circuit comprising: a detector for detecting the presence or absence of a burst signal in a carrier chrominance signal supplied through a chrominance signal amplifier, a reference signal generator for generating by means of ringing a first reference signal synchronous in phase with the burst signal only when the burst signal exists in the carrier chrominance signal, said detector being connected to the output of said generator, an amplifying circuit including a feedback circuit, said amplifying circuit being connected to said reference signal generator, and said feedback circuit being further connected to said detector, said feedback circuit being energized or deenergized depending on the output of said detector, said feedback circuit being deenergized under the existence of the burst signal to cause said amplifying circuit to amplify the first reference signal from said reference signal generator, said feedback circuit being energized under the non-existence of the burst signal to cause said amplifying circuit to constitute a feedback oscillator incorporating said feedback circuit so as to produce a second reference signal, and a demodulator connected to said amplifying circuit and the chrominance signal amplifier, said demodulator demodulating a chrominance signal contained in the carrier chrominance signal in response to the application of both the chrominance signal and the first reference signal during reception of a color television signal, and said demodulator during reception of a monochromatic signal providing an output signal having a d.c. level which is not varIed from that provided during reception of a color television signal owing to the second reference signal being applied to said demodulator.
Claim 2
Dependent Claim
293 words
Circuitry for preventing white balance variations arising when switching from monochromatic television reception to color television reception and vice versa in a television receiver utilizing a reference signal generator of the ringing type, said circuit comprising: a detector for detecting the presence or absence of a burst signal in a carrier chrominance signal supplied through a chrominance signal amplifier, a reference signal generator for generating by means of ringing a first reference signal synchronous in phase with the burst signal only when the burst signal exists in the carrier chrominance signal, said detector being connected to the output of said generator, an amplifying circuit including a feedback circuit, said amplifying circuit being connected to said reference signal generator, and said feedback circuit being further connected to said detector, said feedback circuit being energized or deenergized depending on the output of said detector, said feedback circuit being deenergized under the existence of the burst signal to cause said amplifying circuit to amplify the first reference signal from said reference signal generator, said feedback circuit being energized under the non-existence of the burst signal to cause said amplifying circuit to constitute a feedback oscillator incorporating said feedback circuit so as to produce a second reference signal, and a demodulator connected to said amplifying circuit and the chrominance signal amplifier, said demodulator demodulating a chrominance signal contained in the carrier chrominance signal in response to the application of both the chrominance signal and the first reference signal during reception of a color television signal, and said demodulator during reception of a monochromatic signal providing an output signal having a d.c. level which is not varIed from that provided during reception of a color television signal owing to the second reference signal being applied to said demodulator.
Claim 3
Dependent Claim
123 words
Circuitry for preventing white balance variations as claimed in claim 1, wherein said amplifying circuit comprises a differential amplifying means and a resonance circuit tuned substantially to the frequency of said first reference signal, said differential amplifying means including a first and a second transistor, said first transistor being connected at the base circuit thereof to the output of said reference signal generator and said second transistor being connected at the collector circuit thereof to said resonance circuit and to said demodulator, and said feedback circuit includes switching means interposed between the base circuit of said first transistor and the collector circuit of said second transistor so that said switching means is turned on and offi depending on the output of said detector.
Claim 4
Dependent Claim
111 words
Circuitry for preventing white balance variations as claimed in claim 1, wherein said amplifying circuit comprises a differential amplifying means and a resonance circuit tuned substantially to the frequency of said first reference signal, said differential amplifying means including a first and a second transistor arranged so that said first transistor is connected at the base circuit thereof to the output of said reference signal generator and said second transistor is connected at the collector circuit thereof to said resonance circuit and to said demodulator, and said feedback circuit includes signal phase shifting means interposed between the collector circuit of said first transistor and the base circuit of said second transistor.
Claim 5
Dependent Claim
18 words
Circuitry for preventing white balance variations as claimed in claim 1, wherein said detector is a killer detector.
References Cited (Backward Citations)
US3535437A
Cited
US3541242A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-09-23 | 1978-03-25 | 1978-09-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-23 | 1982-03-25 | 1982-09-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-23 | 1986-03-25 | 1986-09-24 | $7700.00 | Window Closed / Lapsed |