TWO-WAY COMMUNICATION SYSTEM FOR VIDEO AND DIGITAL DATA

• US 3,691,295 A
• Filed: 03/31/1970
• Issued: 09/12/1972
• Est. Priority Date: 03/31/1970
• Status: Expired due to Term

• Current Assignee: Dale E. Fisk
• Original Assignee: Dale E. Fisk
• Inventors: Fisk, Dale E.
• Primary Examiner(s): Cooper, William C.
• Assistant Examiner(s): D'Amico, Thomas
• Application Number:
  US05/024,264
• Time in Patent Office: 896 Days
• Field of Search: 178/58,59,60,DIG.3,5.6 343/175,180 340/172.5 179/2DP,2TV 325/22,21,23
• US Class Current: 370/284
• CPC Class Codes: H04L 5/1423 for simultaneous baseband signals

Abstract

Transmission system for jointly linking a video source to a television display device, and a digital data source to a digital data output by means of a single coaxial cable. A video source and the digital data output are located at one end of the coaxial cable, with the television display device and digital data source located in the vicinity of the other end of the cable. Circuit arrangements are provided at the video source end of the cable, and also at the digital data source end of the cable, for respectively separating the video signal and the digital data signal from each other to thereby facilitate the transmission of video information in one direction through the coaxial cable while digital data is simultaneously transmitted through the cable in the other direction.

Claims

1. A two-way communications system, comprising:

a video signal source;

a television display device substantially spaced apart from said video signal source;

a digital data source;

a digital data output; and

communication means including a single transmission link in the form of a coaxial cable for jointly and directly connecting said video signal source to said display device, and said digital data source to said data output;

said transmission line having one of its ends connected to said video signal source and said digital data output;

the other end of said transmission line being connected to said television display device and said digital data source;

said communication means including a first circuit for cancelling video signal voltage at said digital data output and a second circuit for cancelling digital data voltage at said television display device;

said first cancellation circuit of said communication means including a buffer amplifier connected between said video source and said one end of said line, and said second cancellation circuit comprising an inverting amplifier connected between said other end of said line and said television display device;

whereby said single transmission line provides a two-way communication link between a video source/digital data output and a television display device/digital data source which allows the transmission of video analog information in one direction while binary information is simultaneously transmitted through the link in the other direction.

2. The communications system of claim 1 wherein said inverting amplifier has a finite input impedance and a finite output impedance, said digital data source is connected through a first impedance to the input of said inverting amplifier, and said digital data source is also connected through a second impedance to the output of said inverting amplifier, said first and second impedances being proportioned relative to the gain of the inverting amplifier and the impedances of the line transmission cable, inverting amplifier and television display device to cancel any digital data voltage at the input of said television display device.

3. The communications system of claim 2 wherein said first cancellation circuit comprises a differential amplifier having two input leads and an output lead, said two input leads of said differential amplifier being connected across said buffer amplifier to subtract video voltage from the summation of video voltage and digital voltage thereby to provide a digital voltage signal at the output lead for connection to said digital data output.

4. The communication system of claim 3 wherein said video signal source emanates from a video buffer, the digital data source is produced by a keyboard operated data input device, and said digital data output is fed to a data processor unit.

5. A two way communications system comprising:

a video signal source;

a television display device;

means for directly transmitting video signals in a first direction from said video signal source to said television display device, said video signal transmission means including a singular transmission line unit, an isolation means connected between said video signal source and a first end of said transmission line unit, and an inverting amplifier connected between a second end of said transmiSsion line unit and said television display device;

a digital data source;

a digital data output;

means for transmitting digital data signals in a second direction opposite to said first direction, from said digital data source to said digital data output, said digital data transmission means including said singular transmission unit, circuit means including the connection of said digital data source through a first impedance to said second end of said transmission line unit, and through a second impedance to the output side of said inverting amplifier for cancelling any digital data voltage between said inverting amplifier and said television display device, and differential amplifier means having its inputs connected across said isolation means for subtracting the video signal from said digital data signal to provide a digital data voltage for said digital data output;

whereby said transmission line unit serves as a single communication link between said video source and said digital data source for transmitting video analog information in one direction while binary data is simultaneously transmitted in the other direction.

6. The two-way communications system of claim 5 wherein said isolation means is a buffer amplifier having its input connected to said video signal source and its output connected to the first end of said transmission line unit.

7. The two-way communications system of claim 5 wherein said transmission line unit is a single coaxial cable having its outer shield grounded at each end.

8. The communications system of claim 5 wherein the video signal source is provided by a video buffer, the digital data source is provided by a keyboard operated data input device located in contiguity with said television display device, and said digital data output is connected to a data processor unit.

9. The communications system of claim 7 wherein the inverting amplifier has a finite input impedance and a finite output impedance, said digital data source being connected through the first impedance to the input of said inverting amplifier, said first impedance having a predetermined relationship to the impedance of said coaxial cable, said digital data source being also connected through the second impedance to the output of said inverting amplifier, said second impedance having a predetermined relationship to the output impedance of said inverting amplifier and the input impedance of said television display device.

10. The communications system of claim 9 wherein the digital data source is a keyboard operated data input device located in proximity to the television display device and said data output is a data processor unit.

11. A two-way communications system, comprising:

a video signal source;

a television display device substantially spaced apart form said video signal source;

a digital data source;

a digital data output; and

communication means including a single transmission line for jointly and directly connecting said video signal source to said display device, and said digital data source to said data output;

said transmission line having one of its ends connected to said video signal source and said digital data output;

the other end of said transmission line being connected to said television display device and said digital data source;

said communication means including a first circuit means for cancelling video signal voltage at said digital data output and a second circuit means for cancelling digital data voltage at said television display device;

said first cancellation circuit means including a buffer amplifier connected between said video source and said one end of said line; and

said second cancellation circuit including an inverting amplifier coupled to said other end of said line;

whereby said single transmission line provides a two-way communication link between source/digital video soruce/digital data output and a television display device/digital data Source which allows the transmission of video analog information in one direction while binary information is simultaneously transmitted through the link in the other direction.

12. The communications system of claim 11 wherein the digital data source is located in the vicinity of said television display device and the digital data output is located in the vicinity of said video signal source.