EDUCATIONAL TV BRANCHING SYSTEM

• US 3,825,674 A
• Filed: 05/25/1973
• Issued: 07/23/1974
• Est. Priority Date: 05/25/1973
• Status: Expired due to Term

• Current Assignee: James W.H. Justice
• Original Assignee: James W.H. Justice
• Inventors: Justice, James W. H.
• Primary Examiner(s): Murray, Richard
• Assistant Examiner(s): Godfrey, R. John
• Application Number:
  US05/364,164
• Time in Patent Office: 424 Days
• Field of Search: 178/5.6,DIG.23,5.4R,5.2R,5.8A,5.8R,6.8,7.7,DIG.6 179/15BM
• US Class Current: 348/385.1
• CPC Class Codes: H04N 7/002 Special television systems not provided for by H04N7/007 - H04N7/18 still pictures via a television channel H04N1/00098
• CPC Class Codes: H04N 7/0806 the signals being two or more video signals H04N7/0803, H04N7/081 take precedence

Abstract

A closed circuit or conventional TV broadcast system features the transmitting and receiving of 12 separate pictures and including 12 audio channels on a single television carrier signal such that one of three different pictures appear in each quadrant of the television receiving tube, and including in the receiver, two detectors each preceded by band-pass filters for preventing cross-modulation of the video signals. The system further includes means for blanking out all but one quadrant and for centering and expanding that quadrant to occupy a full television raster. Twelve TV cameras have their video output signals arranged in four groups of three signals. A blanker for each group blanks out all but one quadrant so that three video signals are provided for this quadrant. Blankers for the other groups of video signals operate in a similar manner with respect to the remaining three quadrants. By adding together one video signal from each group there results three composite signals. Each composite signal represents an assembly of four pictures each occupying one quadrant of the TV raster. The composite signals are connected to the Y, I and Q inputs of a modified encoder for transmission on a single TV carrier signal. Twelve audio channels are arranged in two groups of six signal inputs. One group of six signals is inserted in a video signal line during a guard-band blank period as three bursts of amplitude and phase modulated subcarriers. A guard-band blank period is provided in the next video line for transmission of the other set of six audio signals in a similar manner.

Claims

1. An apparatus for transmitting a plurality of separate pictures or scenes on a single television carrier signal such that at least two scenes are available for display in each of four quadrants of a television receiving tube, the combination comprising:

means for producing four groups of video signals, each of said groups including at least two separate video signals, adding means forming at least two summation signals by summing one video signal from each of said groups of video signals whereby each summation signal provides a different scene for display in the respective four quadrants of the television receiving tube, and encoder means receiving said two summation signals and modulating one of said summation signals onto a subcarrier signal for transmission with the other of said summation signal on a single television carrier signal.

2. An apparatus according to claim 1 further comprising blanker means receiving each one of said groups of video signals for limiting the scenes represented thereby for display in one quadrant of the television receiving tube.

3. An apparatus according to claim 2 wherein each of said four groups of video signals comprise three separate video signals, said adding means forming three summation signals by summing one video signal from each group of signals whereby each summation signal provides a different scene for the four quadrants of a TV receiving tube, said encoder means including means for modulating two of said summation signals in a quadrature phase relation onto a subcarrier signal for transmission with the remaining summation signal on a single television carrier signal.

4. An apparatus according to claim 3 wherein said encoder further includes filter means for limiting the frequency domain of each of said three summation signals.

5. An apparatus according to claim 4 further comprising means defining a guard-band blanking period in said subcarrier signal for transmission of pairs of audio signals in the form of bursts of amplitude and phase modulated subcarriers.

6. An apparatus according to claim 4 further comprising:

audio sampling means for a first group of audio signals during a guard-band Blanking period, audio sampling means for a second group of audio signals during a guard-band blanking period, first adding means receiving the first group of sampled audio signals for forming a first audio summation signal, second adding means receiving the second group of sampled audio signals for forming a second audio summation signal, and means for delivering said first and second groups of audio signals to said encoder means to thereby phase and amplitude modulate a sampled audio signal from each group onto a subcarrier signal for transmission on a single television carrier signal.

7. An apparatus according to claim 6 wherein said audio sampling means include a plurality of sample circuitry each for receiving an audio signal, gate means for controlling said sample circuitry, a sample pulse circuit generator for operating said gate means, and a binary circuit for operating said gate means in conjunction with said sample pulse circuit generator.

8. An apparatus according to claim 7 wherein said audio sampling means further include a sync generator producing sync pulses delivered to said sample pulse circuit generator and said binary circuit.

9. An apparatus according to claim 8 wherein said first group of audio signals comprises six separate signals, said second group of audio signals comprises six separate signals, and said audio sampling means being arranged to produce three pairs of audio signals from each group of signals such that said pairs of audio signals are inserted into said guard-band blanking period during one horizontal scan line produced by said video signals.

10. In a television system for transmitting and receiving a plurality of separate pictures or scenes on a single television carrier signal such that at least two scenes are available for display in each of four quadrants of a television receiving tube, the combination comprising:

means for producing four groups of video signals, each of said groups including at least two separate video signals, adding means forming at least two summation signals by summing one video signal from each of said groups of video signals whereby each summation signal provides a different scene for display in the respective four quadrants of the television receiving tube, encoder means receiving said two summation signals and modulating one of said summation signals onto a subcarrier signal for transmission with the other of said summation signals on a single television carrier signal, first detection means for one of said two summation signals, second detection means for the other of said two summation signals, and band-pass filter means preceding each of said detection means to thereby prevent cross-modulation of said summation signals into each other.

11. In a television system for transmitting and receiving a plurality of separate pictures or scenes on a single television carrier to provide three scenes for display in each of four quadrants of a television receiving tube, the combination comprising:

means for producing four groups of video signals, each of said groups comprising three separate video signals, adding means forming YS, IS and QS summation signals by summing one video signal from each of said groups of video signals whereby each summation signal provides a different scene for display in the respective four quadrants of the television receiving tube, encoder means receiving said summation signals and modulating said IS and QS summation signals onto a carrier signal for transmission with said YS summation signal on a single television carrier signal, detector means for said YS summation signal, detector means for said IS and QS summation signals, and band-pass filter means preceding each of said detector means for preventing cross-modulation of said summation signals into each other.

12. In a television system according to claim 11 wherein said band-pass filter means include separate band-pass filters for receiving said IS and QS summation signals, adding means receiving the output signal from said separate band-pass filter means, and demodulating means receiving said QS and IS summation signals from said adding means.

13. In a television system according to claim 12 further comprising amplitude limiting means receiving the output signal from one of said separate band-pass filters for delivering an amplitude limited signal to said adding means.

14. In a television system according to claim 12 further comprising:

blanker means receiving said YS summation signal and the demodulated QS and IS summation signals, a blanking generator having an output signal connected to said blanker means, and switch means receiving said YS, IS and QS summation signals from said blanker means for selective display of one of said summation signals on the television receiving tube.

15. In a television system according to claim 14 further comprising filter means in the signal path of said YS, IS and QS summation signals between said blanker means and said switch means.

16. In a television system according to claim 15 further comprising:

audio sampling means for a first group of audio signals during a guard-band blanking period, audio sampling means for a second group of audio signals during a guard-band blanking period, first adding means receiving the first group of sampled audio signals for forming a first audio summation signal, second adding means receiving the second group of sampled audio signals for forming a second audio summation signal, and means for delivering said first and second groups of audio signals to said encoder means to thereby phase and amplitude modulate a sampled audio signal from each group onto a subcarrier signal for transmission on a single television carrier signal.

17. In a television system according to claim 16 further comprising:

sync separator means receiving said YS summation signal for providing a horizontal sync pulse and a vertical sync pulse, first gate means responsive to said horizontal and vertical sync pulses, second gate means receiving said QS summation signal, third gate means receiving said IS summation signal, and filter means receiving the output signal from each of said second and third gate means for providing a plurality of audio signals.

18. In a television system according to claim 17 wherein said first gate means comprises:

a binary circuit responsive to said vertical sync pulse, a sample pulse generator circuit responsive to said horizontal sync pulse, and gates controlled in response to signals provided by said binary circuit and said sample pulse generator circuit for operation of said second and third gate means.

19. In a television system according to claim 18 wherein said second and third gate means each comprise six gate circuits.