Videoconferencing system

• US 5,374,952 A
• Filed: 02/18/1994
• Issued: 12/20/1994
• Est. Priority Date: 06/03/1993
• Status: Expired due to Fees

• Current Assignee: C-Phone Corporation
• Original Assignee: Target Technology Company LLC
• Inventors: Flohr, Daniel P.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Harvey, David E.
• Application Number:
  US08/199,377
• Time in Patent Office: 305 Days
• Field of Search: 358/83, 358/84, 358/85, 358/86, 348/6, 348/8, 348/10, 348/11, 348/12, 348/13, 348/14, 348/15, 348/16, 348/17, 370/69.1, 370/30, 370/24, 395/200, 455/3.1, 455/5.1, 455/4.1, 455/4.2
• US Class Current: 348/14.08
• CPC Class Codes: H04N 7/147 Communication arrangements, e.g. identifying the communication as a video-communication, intermediate storage of the signals selecting H04Q
• CPC Class Codes: H04N 7/15 Conference systems

Abstract

A videoconferencing network for digital computer workstations that operate on a local area network (LAN) to exchange data. The network includes a signalling local area network (A-LAN), connected to a first port of a plurality of workstations, for transmitting and receiving data signals between selected ones of the workstations and a broadband local area network (B-LAN) connected to a second port of the plurality of workstations, for transmitting and receiving television signals between selected ones of these workstations. Each television signal is transmitted at a selected frequency channel so that no two transmissions interfere. A software program, stored in and operable on the computer of each workstation, generates and receives data messages, transmitted via the A-LAN, to and from the computer of another workstation, respectively. These data messages initiate and control the transmission of the television signals on the B-LAN such that a plurality of television signals are transmitted simultaneously on the B-LAN, with each television signal assigned to a separate frequency channel. The software program in each computer monitors the status of the channel allocations and generates the channel selecting control signals.

Claims

1. A videoconferencing network for a plurality of digital computer stations, wherein each station includes:

(1) an image display;

(2) a digital computer for processing data in accordance with a software program, said computer being connected to supply image and control signals to said display for displaying data thereon;

(3) a video camera for producing video signals representing an image;

(4) a microphone for converting sound into audio signals;

(5) a modulator, connected to said digital computer said video camera and said microphone, for converting video signals received from said camera and associated audio signals received from said microphone into television signals at a frequency channel selected by said computer;

(6) a demodulator, connected to said digital computer, for converting television signals at a frequency channel selected by said computer into video signals and associated audio signals;

(7) a display controller connected to said demodulator for converting video signals received from said demodulator into image and control signals supplied to said display for displaying a video image on said display;

(8) a sound transducer connected to said demodulator for converting audio signals received from said demodulator into sound;

(9) a first input/output port connected to said computer for transmitting and receiving data signals; and

(10) a second input/output port connected to said modulator and said demodulator for transmitting and receiving television signals;

said network comprising, in combination;

(a) a signalling local area network (A-LAN), connected to said first port of a plurality of stations, for transmitting and receiving data signals between selected ones of said stations;

(b) a broadband local area network (B-LAN) connected to said second port of said plurality of stations, for transmitting and receiving television signals between selected ones of said stations, each television signal being transmitted at a selected frequency channel; and

(c) a software program, stored in and operable on said computer of each station, for generating and receiving data messages, transmitted via said A-LAN, to and from the computers of other stations, respectively, said data messages initiating and controlling the transmission of said television signals on said B-LAN such that a plurality of television signals are transmitted simultaneously on said B-LAN, with each television signal assigned to a separate frequency channel, said software program in each computer monitoring the status of the channel allocations and generating channel selecting control signals for said modulator and demodulator.

2. The videoconferencing network defined in claim 1, further comprising a codec, connected to the A-LAN an B-LAN, for digitally encoding and decoding television signals for transmitting and receiving encoded digital television signals to and from a telephone network.

3. The videoconferencing network defined in claim 1, wherein said A-LAN and said B-LAN are divided into a plurality of work groups, said network further comprising an RF bridge connecting the B-LAN of one group with the B-LAN of another work group, for changing the frequency channel of the television signals transmitted on said B-LAN from one work group to another.

4. The videoconferencing network defined in claim 3, wherein said RF bridge includes a plurality of controllable switches connected in parallel, each switch being operative to change the frequency channel of one television signal from a selectable first channel to a selectable second channel.

5. The videoconferencing network defined in claim 4, wherein said RF bridge further includes a processor, responsive to data messages transmitted on said A-LAN, for controlling said plurality of switches to select said first and second channels.

6. The videoconferencing network defined in claim 1, wherein said television signals comprise a non-standard color video and audio signal to provide security against unauthorized access or to effect bandwidth compression.

7. The videoconferencing network defined in claim 6, wherein said color video signal is inverted from a standard video signal.

8. The videoconferencing network defined in claim 1, wherein said television signals comprise a non-standard audio signal to provide security against unauthorized access.

9. The videoconferencing network defined in claim 8, wherein said audio signal is a different modulation type from the standard modulation.

10. The videoconferencing network defined in claim 1, further comprising an analog to digital converter for digitizing said audio signal and a memory for storing portions of said digitized audio signal for subsequent playback.

11. The videoconferencing network defined in claim 1, further comprising an analog to digital converter for digitizing said video signal and a memory for storing portions of said digitized video signal for subsequent playback.

12. The videoconferencing network defined in claim 1, wherein said data messages are transmitted on said A-LAN via a LAN cable and said television signals are transmitted on said B-LAN on a separate CATV cable.

13. The videoconferencing network defined in claim 1, wherein said data messages are transmitted on said A-LAN via a prescribed frequency channel on a CATV cable and wherein said television signals are also transmitted on said CATV cable.

14. The videoconferencing network defined in claim 1, wherein said video signal and said audio signal are digital signals;

wherein said modulator includes a digital compression stage, connected to receive said digital signals, for producing compressed video and audio digital signals, said modulator being operative to superimpose said digital signals on a selected carrier to produce a digital television signal.

15. The videoconferencing network defined in claim 14 wherein said demodulator includes a tuner for detecting digital signals from a digital television signal at a selected frequency and a decoder for decoding said signals to reproduce the video digital signals and said associated audio digital signals.

16. The videoconferencing network defined in claim 1, wherein said A-LAN and said B-LAN are divided into a plurality of work groups, with each work group having assigned thereto a plurality of private channels for exclusive use within the work group plus at least one bridge output frequency channel and at least one bridge input frequency channel, the network further comprising an RF bridge, connecting the B-LAN of one group with the B-LAN of another work group, for passing only television signals on the bridge output channels from a given work group and passing only television signals on the bridge input channels to said given work group.

17. The videoconferencing network defined in claim 16, wherein said RF bridge further comprises two frequency bandpass filters connected in parallel, one bandpass filter operative to pass the frequency range of the bridge output channels and the other bandpass filter operative to pass the frequency range of the bridge input channels.

18. The videoconferencing network defined in claim 1, wherein each station further comprises (1) a video signal scrambler, connected to said modulator of such station, for modifying the video signal to provide security against unauthorized access, and (2) a video descrambler, connected to said demodulator of such station, for unmodifying the video signal to permit viewing of the video image represented thereby on the image display of the respective station.

19. The videoconferencing network defined in claim 1, wherein said data messages comprise a source address portion and a destination address portion.

20. The videoconferencing network defined in claim 1, wherein said data messages comprise a type identification portion.

21. The videoconferencing network defined in claim 1, wherein said data messages comprise network control messages and call progress messages.

22. The videoconferencing network defined in claim 21, wherein said network control messages comprise station sign-on and station sign-off messages.

23. The videoconferencing network defined in claim 21, wherein said network control messages comprise channel request and channel-in-use messages.

24. The videoconferencing network defined in claim 21, wherein said call progress messages comprise call request, call answer and call hang-up messages.

25. The videoconferencing network defined in claim 24, wherein said call progress messages comprise a call hang-up acknowledge message.

26. The videoconferencing network defined in claim 21, wherein said call progress messages comprise a call busy message.

27. The videoconferencing network defined in claim 21, wherein said call progress messages comprise a call private message.

28. The videoconferencing network defined in claim 21, wherein said call progress messages comprise an answering machine pick-up message.

29. The videoconferencing network defined in claim 1, wherein said digital computer comprises a memory, and wherein said digital computer has stored in said memory a state table comprising the current allocation of frequency channels for use by said software program, and wherein said software program is operative to update the frequency allocations in said state table upon receipt of prescribed data messages transmitted via said A-LAN.

30. The videoconferencing network defined in claim 29, wherein said prescribed data messages include channel request and channel release messages.

31. The videoconferencing network defined in claim 29, wherein said prescribed data messages include system status messages.

32. The videoconferencing network defined in claim 29, wherein said state table further comprises a list of each active station connected to said A-LAN and B-LAN and said software program is operative to update said list of active stations in said state table upon receipt of certain data messages transmitted via said A-LAN.

33. The videoconferencing network defined in claim 32, wherein said certain data messages are station sign-on, station sign-off and call progress messages.

34. The videoconferencing network defined in claim 1, wherein said digital computer comprises a memory, and wherein said digital computer has stored in said memory a directory for use by said software program comprising the identity of all stations connectable to said A-LAN and B-LAN, and wherein said software program is operative to update the identity of said stations in said directory.

35. The videoconferencing network defined in claim 34, wherein said software program transmits a data message to another workstation requesting information concerning the user of that workstation, and wherein said software program stores the user information in said directory, upon receipt thereof from said other workstation.

36. The videoconferencing network defined in claim 35, wherein said information includes the name of that workstation user.

37. The videoconferencing network defined in claim 36, wherein said information further includes a video image of that workstation user.

38. The videoconferencing network defined in claim 1, wherein at least said B-LAN includes a CATV cable.

39. The videoconferencing network defined in claim 38, wherein said B-LAN includes a plurality of CATV cables arranged in parallel and an RF switch, coupling each CATV cable to the second input/output port of each station, for selecting the CATV cable which is connected to said input/output port.

40. The videoconferencing network defined in claim 1, further comprising a telephone private automatic branch exchange (PABX) for switching between a plurality of telephone trunk lines and a plurality of telephone station lines, and wherein each station further comprises:

(i) a PABX interface circuit, connected to one of said telephone station lines;

(ii) a keypad for entry of a telephone number; and

(iii) a telephone handset.