TRANSMISSION SYSTEM FOR AUDIO AND CODING SIGNALS IN EDUCATIONAL TV

• US 3,916,092 A
• Filed: 05/25/1973
• Issued: 10/28/1975
• 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:
  US05/364,163
• Time in Patent Office: 886 Days
• Field of Search: 178/DIG.23,5.6,5.2R,5.8R 179/15BM 358/12
• US Class Current: 348/478
• CPC Class Codes: H04N 7/0806 the signals being two or more video signals H04N7/0803, H04N7/081 take precedence

Abstract

An educational TV system features a transmitter receiver for a plurality of audio and coding signals along with multiple pictures. Bursts of audio signals are modulated in pairs onto 3.6 megahertz quadrature phase subcarriers in the same way as conventional I and Q video signals are modulated onto a subcarrier in conventional TV systems. Modulated onto each quadrature phase of the 3.6 megahertz subcarrier is an audio pulse signal. The resulting burst of phase and amplitude modulated subcarriers are produced during a blanked guard-band interval. This process is repeated with another pair of audio signals whereby two time divided bursts of modulated subcarriers are produced during the blanked guard-band interval which is located midway within the horizontal scan line time period used to transmit modulated video signals on a subcarrier. Coding signals are introduced onto the carrier signal during the time of the back porch of the video signal. In the receiver, after detecting and demodulating the bursts of audio signals, switching and logic circuitry perform both audio and picture switching operations to select an audio signal for driving a loud-speaker or headphone. The conventional audio FM channel associated with TV signal transmissions is also provided and operates in the conventional manner.

Claims

1. A transmitter apparatus for a plurality of input audio signals and video signals, all of which are modulated onto a subcarrier for transmission on a single TV carrier signal, the combination comprising:

means for generating a horizontal sync pulse between successive horizontal scan lines forming said video signals;

blanking means in the signal path of said video signals for defining a blanked guard-band interval at a time apart from a generated horizontal sync pulse;

means for sampling each input audio signal, and means for amplitude modulating the sampling of said plurality of audio signals onto a subcarrier during said blanked guard-band interval apart from which interval said video signals are modulated onto the subcarrier during each horizontal picture scan line.

2. A transmitter apparatus according to claim 1 wherein said means for samplings is further defined to include:

gate means for sampling each of said plurality of audio signals during each horizontal picture scan period, said apparatus further comprising, monostable multivibrator means rendering conductive said gate means for delivering sampled audio signals during said blanked guard-band interval to said means for amplitude modulating.

3. A transmitter apparatus according to claim 1 further comprising:

phase shift means for said subcarrier signal connected to said means for amplitude modulating to thereby amplitude and phase modulate pairs of audio signals forming part of said plurality of audio signals onto the subcarrier signal during said blanked guardband interval.

4. A transmitter apparatus according to claim 3 further comprising:

gate means for sampling each one of said plurality of audio signals during each horizontal picture scan line, a first monostable multivibrator means rendering conductive two of said gate means for delivering a first pair of sampled audio signals for amplitude and phase modulation onto said subcarrier during said blanked guard-band interval, and second monostable multivibrator means, rendering conductive two other of said gate means for delivering a second pair of sampled audio signals for amplitude and phase modulation onto said subcarrier during said blanked guard-band interval.

5. A transmitter according to claim 1 wherein said blanked guard-band interval occurs during a portion of the time interval during each horizontal picture scan line used to transmit luminance and chrominance video signals on a subcarrier signal.

6. A transmitter according to claim 5 further comprising adding means for introducing coding signals onto said subcarrier during the occurring time period of vertical blanking between successive horizontal picture scan lines.

7. A transmitter according to claim 1 further comprising matrix means receiving said video signals wherein there is defined said blanked guard-band interval during each horizontal picture scan line.

8. A transmitter according to claim 7 wherein said video signals correspond to a different scene for display in four quadrants of a television receiving tube.

9. An educational television system including the use of a plurality of input audio signals and video signals all of which are carried by a subcarrier on a single RF carrier signal, a transmitter comprising the combination of:

gate sampler means for each of said plurality of audio signals, pulse control means for rendering conductive said gate sampler means to provide time delayed pairs of said audio signals, means for generating a horizontal sync pulse between successive horizontal scan lines forming said video signal;

blanker means in the sIgnal path of said video signals for defining a blanked guard-band interval at a time apart from a generated horizontal sync pulse, and means for modulating one audio signal of each pair onto a subcarrier in a phase displaced relation during said blanked guard-band interval apart from which interval said video signals are modulated onto the subcarrier during each horizontal picture scan line.

10. An educational television system according to claim 9 wherein said pulse control means include a first monostable multivibrator for producing a time delayed first signal, a second monostable multivibrator responsive to said first signal for producing a signal pulse to render conductive two of said gate sampler means, and a third monostable multivibrator responsive to a signal from said second monostable multivibrator for producing a signal pulse to render conductive two other of said gate sampler means.

11. An educational television system according to claim 10 wherein said pulse control means further include a fourth monostable multivibrator actuated in response to a signal from said second monostable multivibrator for producing a time delayed second signal to actuate said third monostable multivibrator.

12. An educational television system according to claim 11 further comprising quadrature phase shift means includng a 3.6 megahertz subcarrier signal for delivering quadrature phase subcarrier signals to said means for modulating.

13. An educational television system according to claim 12 further comprising adding means for introducing a plurality of coding signals during the occurring time period of vertical blanking.

14. An educational television system including a receiver for an RF carrier signal having a subcarrier signal containing modulated video signals and bursts of modulated pairs of audio input signals during a blanked guard-band interval located apart from a horizontal sync pulse in the video signals, said receiver comprising the combination of:

detector means for demodulating said RF carrier signal to recover said subcarrier signal, means for demodulating said subcarrier signal to recover said video signals which include pairs of audio signals arranged within said blanked guard-band interval, gate means receiving the demodulated subcarrier signals, gate control means for rendering conductive said gate means during said blanked guard-band interval to recover the audio signals from each pair thereof, speaker means for said audio signals, and switching means for selecting one of the audio signals to drive said speaker means.

15. An educational television system according to claim 14 wherein said receiver further comprises:

guard-band blanker means in the signal path of the demodulated video signals, and blanking signal means for controlling said blanker means to provide a blanked guard-band interval in the demodulated video signals during recovery of the audio signal by said gate control means.

16. An educational television system according to claim 15 wherein said gate control means include a first monostable multivibrator for producing a time delayed first signal, a second monostable multivibrator responsive to said first signal for producing a signal pulse to render conductive two gates of said gate means, and a third monostable multivibrator responsive to a signal from said second monostable multivibrator for producing a signal pulse to render conductive two other gates of said gate means.

17. An educational television system according to claim 16 wherein said gate control means further include a fourth monostable multivibrator actuated in response to a signal from said second monostable multivibrator for producing a time delayed second signal to actuate said third monostable multivibrator.

18. An educational television system according to claim 17 further comprising filter means for each audio signal passing between said gate means and said switching means.

19. An educational Television system according to claim 18 further comprising:

code signal gate means receiving a video signal, and signal generating means for rendering conductive said code signal gate means during the occurring time period of vertical blanking.

20. An educational television system according to claim 19 further comprising matrix means receiving said demodulated video signals for providing decoded video signals to said guard-band blanker means, said decoded video signals corresponding to composite frame of different scenes for display in four quadrants of the receiving tube.