Audio and video plural source time division multiplex for an educational TV system

• US 3,902,007 A
• Filed: 06/26/1973
• Issued: 08/26/1975
• Est. Priority Date: 06/26/1973
• 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): Britton, Howard W.
• Assistant Examiner(s): Stellar, George G.
• Application Number:
  US05/373,727
• Time in Patent Office: 791 Days
• Field of Search: 178/5.6,5.8R,DIG.23
• US Class Current: 348/482
• CPC Class Codes: H04N 7/0806 the signals being two or more video signals H04N7/0803, H04N7/081 take precedence
• CPC Class Codes: H04N 7/084 with signal insertion during the horizontal blanking interval only

Abstract

One or more audio signals are transmitted and received on conventional video subcarriers during blanked guard-band intervals in the horizontal scan lines forming one, or less than all, of a plurality of branched video pictures. In the branching system, a single T.V. channel is used to transmit and receive two or more separate video pictures by selecting a horizontal scan line from one picture, disregarding successive scan lines thereof until one successively occurring scan line from all of the pictures to be transmitted has been selected and then selecting the next available scan line of the first picture. This processing is then repeated continuously for all the scan lines making up the frame of the pictures. In the preferred form, the blanked guard-band interval occurs only during horizontal scan lines for one of two pictures transmitted. Audio signals are sampled at the standard video scan rate to form audio bursts, two of which are inserted into only those horizontal scan lines having a blanked interval. When one audio signal is transmitted, it is branched into two lines, one including a time delay medium. In the receiver, the previously undelayed audio bursts are time delayed and recombined with the transmitter delayed audio bursts to provide a wide bandwidth audio signal. When bursts of two or more audio signals are received, gating is used to recover the separate audio signals.

Claims

2. The method according to claim 1 including the additional step of delaying the audio signal in one of said audio signal transmission lines for a period of time corresponding to at least one video scan line time period.

3. The method according to claim 2 wherein said signal transmission lines each receive the same audio signal.

4. The method according to claim 1 wherein said signal transmission lines each receive a separate and independent audio signal.

5. The method according to claim 1 wherein the continuous sampling of the audio signal in each of said signal transmission lines produces audio bursts occurring at different times.

6. The method according to claim 5 wherein the continuous sampling of the audio signal in each of said signal transmission lines produces an audio burst for every two video scan lines transmitted.

7. In a television branching system, the method of recovering from a video subcarrier within a single channel frequency in a receiver at least one audio signal transmitted along with at least one and less than all of two or more separate and branched video pictures, said audio signals being transmitted in the form of a plurality of audio bursts during a blanked guard-band interval which occurs within the video intelligence portion of the horizontal scan lines selected to transmit at least one and less than all of two or more separate and branched video pictures, said method including the steps of:

receiving said video subcarrier modulated with said two or more separate and branched video pictures of which at least one and less than all contain a blanked band in the video when displayed on the face of a television display tube, said blanked band corresponding to said blanked guard-band interval;

selecting a video signal from said video subcarrier corresponding to horizontal scan lines forming only the separate and branched video pictures which when displayed include said blanked band and thereby selecting only the horizontal scan lines including said plurality of audio bursts during the blanked guard-band interval within the video intelligence portion of the scan lines;

branching the signal path of the selected signal which includes said plurality of audio bursts during the blanked guard-band interval;

time delaying the selected signal in one of the branched signal paths;

gating the signals corresponding to both the delayed and undelayed signals in the branched signal path to recover said plurality of audio bursts from the blanked guard-band intervals therein;

detecting the gated audio bursts to form an audio signal; and

amplifying the formed audio signal to drive a sound transducer.

8. The method according to claim 7 wherein said time delaying the signal corresponding to the horizontal scan line signal in one of the signal paths occurs for a period of time corresponding to the time period of a horizontal scan line.

9. The method according to claim 7 including the step of detecting said plurality of audio bursts to form an audio signal.

10. The method according to claim 7 wherein said plurality of audio signal bursts are gated from the signal corresponding to the undelayed horizontal scan line at intervals of time occurring in a time displaced manner from the intervals of time for gating the signal corresponding to the delayed horizontal scan lines.

11. The method according to claim 7 wherein said gating the signal occurs in a manner to supply a signal for said time delaying.

12. The method according to claim 9 including the step of amplifying the signal produced from said plurality of audio bursts to form an audio output signal for driving a sound transducer.

13. In a television branching system, an apparatus to transmit within a single television frequency channel one or more audio signals along with at least one and less than all of two or more separate and branched video pictures using the same video subcarrier, said apparatus comprising:

gate means including an add circuit to form fields of a video signal corresponding to selected horizontal scan lines for transmitting branched video pictures, said means being operable to select a horizontal scan line corresponding to a first video picture and then selecting the next horizontal scan line for transmission from a second picture which is then succeeded by selecting a subsequently occurring horizontal scan line from said first picture;

means for sampling said audio signals to produce trains of time-separated audio bursts which trains of audio bursts occur at a rate less than the occurring rate of horizontal scan lines selected to form the fields of branched audio pictures;

blanking means responsive to control pulses occurring at a rate less than the horizontal scan rate of said fields of video signal, said blanking means being coupled in the video signal path of at least one and less than all of the branched video signals for defining a guard-band blanked interval within the video intelligence portion of the horizontal scan lines selected by said gate means to form at least one and less than all of the branched video pictures; and

means including an encoder receiving the trains of time-separated audio bursts and receiving the signal corresponding to the branched video pictures for modulating the same video subcarrier with both the video signal corresponding to selected horizontal scan lines forming the branched video picture and the train of time-separated audio bursts only during said quard-band blanked interval.

14. The apparatus according to claim 13 wherein said means for sampling include first and second audio signal samplers and said means for controlling including monostable multivibrator means for rendering said second sampler conductive, said apparatus further comprising means receiving horizontal sync pulses for producing pulses to control said first sampler and said monostable multivibrator.

15. The apparatus according to claim 14 further comprising delay means in the path of the audio signal delivered to one of said audio signal samplers.

16. The apparatus according to claim 14 wherein said first and second audio signal samplers receive separate and independent audio signals.

17. The apparatus according to claim 14 further comprising means for combining the pulses delivered from said first and second samplers to form said train of time-separated audio bursts.

18. The apparatus according to claim 13 further comprising a means for receiving said audio signal bursts transmitted on said video subcarrier and means for detecting said audio signal bursts for recovering an audio signal represented thereby.

19. The apparatus according to claim 18 further comprising means for delivering video signals to said means for encoding in the form of a selected horizontal scan line from one of said separate video pictures followed by a selected horizontal scan line from a second of said separate video pictures which is succeeded by a subsequent horizontal scan line from said first picture.

20. In a television branching system, an apparatus for receiving within a single television channel one or more audio signals along with two or more branched and separate video pictures on the same video subcarrier, said audio signals being transmitted in the form of a plurality of audio bursts during a blanked guard-band interval which occurs within the video intelligence portion of the horizontal scan lines selected a transmit at least one and less than all of two or more of the separate and branched video pictures, said apparatus comprising:

means for detecting said video subcarrier modulated with said two or more separate and branched video pictures of which at least one and less than all contain a blanked band in the video intelligence portion when displayed on the face of a television display tube, said blanked band corresponding to said blanked guard-band interval containing a Plurality of audio bursts;

gate means coupled to said means for detecting;

line sharing pulse generator means for controlling said gate means to select from the video subcarrier only the horizontal scan lines containing the blanked guard-band interval and forming at least one and less than all of the branched and separate video pictures;

means coupled to said gate means for branching into separate signal paths the signal corresponding to the selected horizontal scan lines having the plurality of audio bursts within the blanked guard-band interval;

means coupled in one of the branched signal paths for delaying the conducted signal which includes at least a plurality of audio bursts;

gate means for selecting audio bursts from the signals conducted in the branched signal paths;

means for adding the audio burst signals from both branched signal paths; and

detector means receiving the added audio burst signals for producing an audio signal corresponding to the audio signal bursts.

21. The apparatus according to claim 20 further comprising:

filter means for receiving the audio signal from said means for detecting an audio signal; and

means for amplifying the signal from said filter means.

22. The apparatus according to claim 20 wherein said gate means for selecting includes:

first gate means in one signal path formed by said means for branching;

second gate means in the other signal path formed by said means for branching; and

audio gate pulse generator means for producing signals to render said first and second gates conductive to said audio bursts occurring during said blanked guard-band interval.

23. The apparatus according to claim 20 wherein said gate means for selecting includes:

means for gating the signal from said means for adding; and

audio gate pulse generator means for rendering said means for gating conductive to said audio burst occurring during said blanked guard-band interval.