US3845498A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Receiver for an educational branching system
Assignee: Westinghouse Electric Corp
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Filing: 1973-05-25
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Granted: 1974-10-29
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Expires: 1993-05-25
Abstract
Abstract A closed circuit or conventional broadcast system used as an educational TV system features a multiplicity of pictures for branching purposes that are transmitted and received within a single TV frequency channel by modification to the encoder and decoder that are normally used for the transmission of NTSC color pictures. The receiver includes a coding and switching logic means to provide any one of three completely independent monochrome picture programs and conventional color television programs, all of which occupy a full TV raster. The changes to the encoding and decoding circuits avoid modification to the NTSC synchronizing waveforms and the relative positions of the video, audio and color subcarrier frequencies.
Inventors
- 👤 J Justice
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 21:39
CPC Classifications
H; H04; H04N; H04N11/00; H04N11/06; H04N11/12; H04N11/14; H04N7/00; H04N7/08; H04N7/081
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
225 words
In television system for transmitting and receiving at least two separate and independent video signals using a single radiofrequency carrier signal, the combination of: means for producing a complete first video signal corresponding to a first video image, a filter for limiting the upper frequency of said first video signal, means for producing a complete second video signal corresponding to a second video image, said second video signal being separate and independent from said first video signal, a filter for limiting the upper frequency of said second video signal, means for modulating the filtered second video signal onto a subcarrier to form a modulated subcarrier having a frequency domain essentially non-overlapping with the frequency domain of the filtered first video signal, means for combining the filtered first complete video signal and the filtered second complete video signal after modulation with a subcarrier to form a composite video signal, means for transmitting said composite signal on a single radiofrequency carrier signal, means for detecting the complete first video signal and the modulated subcarrier with the complete second video signal from said single radio-frequency carrier signal, means for demodulating the modulated subcarrier to recover the complete second video signal, and switching means for selecting one of the detected complete video signals for display of the video image represented thereby upon a cathode-ray tube of a television receiver.
Claim 2
Dependent Claim
225 words
In television system for transmitting and receiving at least two separate and independent video signals using a single radiofrequency carrier signal, the combination of: means for producing a complete first video signal corresponding to a first video image, a filter for limiting the upper frequency of said first video signal, means for producing a complete second video signal corresponding to a second video image, said second video signal being separate and independent from said first video signal, a filter for limiting the upper frequency of said second video signal, means for modulating the filtered second video signal onto a subcarrier to form a modulated subcarrier having a frequency domain essentially non-overlapping with the frequency domain of the filtered first video signal, means for combining the filtered first complete video signal and the filtered second complete video signal after modulation with a subcarrier to form a composite video signal, means for transmitting said composite signal on a single radiofrequency carrier signal, means for detecting the complete first video signal and the modulated subcarrier with the complete second video signal from said single radio-frequency carrier signal, means for demodulating the modulated subcarrier to recover the complete second video signal, and switching means for selecting one of the detected complete video signals for display of the video image represented thereby upon a cathode-ray tube of a television receiver.
Claim 3
Dependent Claim
76 words
The combination according to claim 1 further comprising means for producing three interdependent color video signals, matrixing means receiving said color video signals for delivering Y, I and Q video signals to said means for transmitting, switch means for removing said matrixing means from the signal paths of said first and second complete video signals, and switch means for removing said filter for said first video signal from the signal path of said color video signals.
Claim 4
Dependent Claim
42 words
The combination according to claim 2 further comprising means for decoding said Y, I and Q video signals, and means for connecting the decoded Y, I and Q signals to the red, green and blue control grids of a color cathode-ray tube.
Claim 5
Dependent Claim
41 words
The combination according to claim 3 wherein said filter for the complete first video signal comprises an approximate 2.0 MHZ low-pass filter, said combination further comprising switch means for passing said complete first video signal through said 2.0 MHZ low-pass filter.
Claim 6
Dependent Claim
29 words
The combination according to claim 4 further comprising an approximate 2.0 MHZ low-pass filter in the signal path of said complete first video signal following said means for detecting.
Claim 7
Dependent Claim
22 words
The combination according to claim 1 wherein said filter for the complete first video signal includes an approximately 2.0 MHZ low-pass filter.
Claim 8
Dependent Claim
25 words
The combination according to claim 6 further comprising means following said filter means in the signal path of said video signals for time synchronization thereof.
Claim 9
Dependent Claim
238 words
In a television system for transmitting and receiving three separate and independent video signals on a single radio-frequency carrier signal, the combination of: means for producing a YS video signal representing a complete and independent video imagE, means for producing an IS video signal representing a complete and independent video image, means for producing a QS video signal representing a complete and independent video image, said YS, QS and IS video signals being separate and independent from each other, a filter for limiting the upper frequency of said YS video signal, filters for limiting the upper frequencies of said IS and QS video signals, a quadrature-phased subcarrier for modulation by the filtered IS and QS video signals to form a quadrature-phased modulated subcarrier having a frequency domain essentially non-overlapping with the frequency domain of the filtered YS video signal, means for combining the filtered YS video signal and the filtered QS and IS video signals after modulation onto the quadrature-phased subcarrier to form a composite signal, means for transmitting said composite signal on a single radio-frequency carrier signal, means for detecting the YS signal and the modulated quadrature-phased subcarrier from said single radio-frequency carrier signal, means for demodulating the QS and IS video signals from said quadrature-phased subcarrier, and switching means for selecting one of the transmitted YS, IS and QS video signals for display of the video image represented thereby upon a cathode-ray tube of a receiver.
Claim 10
Dependent Claim
238 words
In a television system for transmitting and receiving three separate and independent video signals on a single radio-frequency carrier signal, the combination of: means for producing a YS video signal representing a complete and independent video imagE, means for producing an IS video signal representing a complete and independent video image, means for producing a QS video signal representing a complete and independent video image, said YS, QS and IS video signals being separate and independent from each other, a filter for limiting the upper frequency of said YS video signal, filters for limiting the upper frequencies of said IS and QS video signals, a quadrature-phased subcarrier for modulation by the filtered IS and QS video signals to form a quadrature-phased modulated subcarrier having a frequency domain essentially non-overlapping with the frequency domain of the filtered YS video signal, means for combining the filtered YS video signal and the filtered QS and IS video signals after modulation onto the quadrature-phased subcarrier to form a composite signal, means for transmitting said composite signal on a single radio-frequency carrier signal, means for detecting the YS signal and the modulated quadrature-phased subcarrier from said single radio-frequency carrier signal, means for demodulating the QS and IS video signals from said quadrature-phased subcarrier, and switching means for selecting one of the transmitted YS, IS and QS video signals for display of the video image represented thereby upon a cathode-ray tube of a receiver.
Claim 11
Dependent Claim
74 words
The combination according to claim 8 further comprising a means for producing interdependent red, green and blue color video signals corresponding to video image, means for matrixing said red, green and blue video signals to form a luminance Y and chromance I and Q video signals, and switch means for removing said means for matrixing said red, green and blue video signals from the signal paths of said YS, IS and QS video signals.
Claim 12
Dependent Claim
56 words
The combination according to claim 9 further comprising means for decoding said Y, I and Q video signals, switching means for connecting the decoded Y, I and Q video signals to the red, green and blue grids of a color cathode-ray tube of a receiver, and coding and switching logic means for controlling said switching means.
Claim 13
Dependent Claim
24 words
The combination according to claim 10 further comprising an approximate 2.0 MHZ filter in the YS video signal path from said means for detecting.
Claim 14
Dependent Claim
26 words
The combination according to claim 8 wherein said filter for limiting the upper frequency of said YS video signal includes an approximate 2.0 MHZ low-pass filter.
Claim 15
Dependent Claim
52 words
The combination according to claim 12 wherein said filter means for limiting the upper frequency of said IS and QS video signals include an approximately 1.5 MHZ filter in the signal path of said IS video signal and an approximately 0.5 MHZ filter in the signal path of said QS video signal.
Claim 16
Dependent Claim
27 words
The combination according to claim 13 further comprising synchronizing means in the signal paths of the filtered YS and IS video signals preceding said means for combining.
Claim 17
Dependent Claim
26 words
The combination according to claim 8 wherein said YS, IS and QS video signals are concurrent and separate monochrome video signals from three individual television cameras.
References Cited (Backward Citations)
US2875271A
Cited
US2912492A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-28 | 1978-04-29 | 1978-10-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-28 | 1982-04-29 | 1982-10-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-28 | 1986-04-29 | 1986-10-29 | $7700.00 | Window Closed / Lapsed |