Isdn multimedia communications system

Claim 2

A multimedia communications terminal station comprising: a source for generating a video-to-data mode switching command signal and a data-to-video mode switching command signal; a central processing unit responsive to said video-to-data mode switching command signal for generating an outgoing data mode identifier indicating that a signal to be transmitted to a distant station is computer-generated data and an outgoing video-to-data mode switching signal, indicating the distant station to switch to a data mode of reception, and responsive to said data-to-video mode switching command signal for generating an outgoing video mode identifier indicating that a signal to be transmitted to the distant station is a video signal and an outgoing data-to-video mode switching signal indicating the distant station to switch to a video mode of reception, said outgoing video-to-data mode switching signal and said outgoing data-to-video mode switching signal being further generated respectively in response to receipt of an incoming data mode identifier and an incoming video mode identifier from said distant station, respectively indicating the terminal station to switch to data and video modes of reception; LAPB (link access procedure balanced) control means for exchanging signals with said central processing unit; video coder/decoder means for generating an outgoing digital video signal and decoding an incoming digital video signal; multiplexer means for synchronously multiplexing said outgoing digital video signal from the video coder/decoder means with said outgoing data mode identifier to generate an outgoing composite video signal; demultiplexer means for synchronously demultiplexing an incoming composite video signal from said distant station into said incoming data mode identifier and a digital video signal, and supplying the demultiplexed video signal to said video coder/decoder means; an ISDN (integrated services digital network) interface for interfacing the terminal station with an integrated services digital network to which said distant station is also terminated; and switching means responsive to said outgoing video-to-data mode switching signal for coupling said LAPB control means to said ISDN interface for allowing said central processing unit to exchange computer-generated data and said incoming and outgoing video mode identifiers with said distant station, and responsive to said outgoing data-to-video mode switching signal for coupling said LAPB control means to said interface via said video coder/decoder means to exchange said outgoing and incoming composite video signals with said distant station, allowing said demultiplexer means to supply said incoming data mode identifier to said central processing unit via said LAPB control means and allowing said central processing unit to supply said outgoing data mode identifier to said multiplexer means via said LAPB control means.

Claim 3

A multimedia communications terminal station as claimed in claim 1, wherein said video-to-data mode switching signal is generated after said data mode identifier is transmitted to said distant station.

Claim 4

A multimedia communications terminal station as claimed in claim 1, wherein said central processing unit further generates an acknowledgment signal in response to receipt of said incoming data mode identifier from a distant station, and generates said video-to-data mode switching signal in response to receipt of said acknowledgment signal from a distant station.

Claim 5

A multimedia communications terminal station as claimed in claim 1, wherein said LAPB control means is formed by an LSI (large scale integration) circuit.

Claim 6

A multimedia communications terminal station as claimed in claim 1, further comprising voice coder/decoder means connected to said ISDN interface for decoding an incoming voice digital signal from said distant station via said interface and transmitting an outgoing voice digital signal to said distant station via said interface, said interface multiplexing said outgoing voice digital signal with said outgoing composite video signal for transmission to said distant station and demultiplexing signals from said distant stations into said incoming voice digital signal and said incoming composite video signal.

Claim 7

A multimedia communications terminal station as claimed in claim 1, wherein said central processing unit generates a dummy code containing a specified bit sequence during a period between the time at which said outgoing data-to-video mode switching signal is generated and the time at which said outgoing video-to-data mode switching signal is generated, said multiplexer means multiplexing the dummy code with said outgoing digital video signal during said period so that the multiplexed dummy code occupies the same signal position of the outgoing composite video signal as said outgoing data mode identifier.

Claim 8

A multimedia communications system comprising a plurality of terminal stations interconnected by an integrated services digital network to which a database is also connected, each of said terminal stations being operable as a data terminal for exchanging computer-generated data with a distant station or accessing said database during a data communication mode and operable as a video terminal for exchanging digital video signals with said distant station during a video communication mode, each of said terminal stations comprising: a source for generating a video-to-data mode switching command signal and a data-to-video mode switching command signal; a central processing unit responsive to said video-to-data mode switching command signal for generating an outgoing data mode identifier indicating that a signal to be transmitted to a distant station is computer-generated data and an outgoing video-to-data mode switching signal, indicating the distant station to switch to a data mode of reception, and responsive to said data-to-video mode switching command signal for generating an outgoing video mode identifier indicating that a signal to be transmitted to the distant station is a video signal and an outgoing data-to-video mode switching signal indicating the distant station to switch to a video mode of reception, said outgoing video-to-data mode switching signal and said outgoing data-to-video mode switching signal being further generated respectively in response to receipt of an incoming data mode identifier and an incoming video mode identifier from said distant station, respectively indicating the terminal station to switch to data and video modes of reception; LAPB (link access procedure balanced) control means for exchanging signals with said central processing unit; video coder/decoder means for generating an outgoing digital video signal and decoding an incoming digital video signal; multiplexer means for synchronously multiplexing said outgoing digital video signal from the video coder/decoder means with said outgoing data mode identifier to generate an outgoing composite video signal; demultiplexer means for synchronously demultiplexing an incoming composite video signal from said distant station into said incoming data mode identifier and a digital video signal, and supplying the demultiplexed video signal to said video coder/decoder means; an ISDN (integrated services digital network) interface for interfacing the terminal station with said integrated services digital signal network to which said distant station is also terminated; voice coder/decoder means connected to said ISDN interface for decoding an incoming voice digital signal from said distant station via said interface and transmitting an outgoing voice digital signal to said distant station via said interface, said interface multiplexing said outgoing voice digital signal with said outgoing composite video signal for transmission to said distant station and demultiplexing signals from said distant stations into said incoming voice digital signal and said incoming composite video signal; and switching means responsive to said outgoing video-to-data mode switching signal for coupling said LAPB control means to said ISDN interface for allowing said central processing unit to exchange said computer-generated data and said incoming and outgoing video mode identifiers with said distant station and to access said database, and responsive to said outgoing data-to-video mode switching signal for coupling said LAPB control means to said interface via said multiplexer and demultiplexer means for allowing said video coder/decoder means to exchange said outgoing and incoming composite video signals with said distant station, allowing said demultiplexer means to supply said incoming data mode identifier to said central processing unit via said LAPB control means and allowing said central processing unit to supply said outgoing data mode identifier to said multiplexer means via said LAPB control means.

Claim 9

A multimedia communications system comprising a plurality of terminal stations interconnected by an integrated services digital network to which a database is also connected, each of said terminal stations being operable as a data terminal for exchanging computer-generated data with a distant station or accessing said database during a data communication mode and operable as a video terminal for exchanging digital video signals with said distant station during a video communication mode, each of said terminal stations comprising: a source for generating a video-to-data mode switching command signal and a data-to-video mode switching command signal; a central processing unit responsive to said video-to-data mode switching command signal for generating an outgoing data mode identifier indicating that a signal to be transmitted to a distant station is computer-generated data and an outgoing video-to-data mode switching signal, indicating the distant station to switch to a data mode of reception, and responsive to said data-to-video mode switching command signal for generating an outgoing video mode identifier indicating that a signal to be transmitted to the distant station is a video signal and an outgoing data-to-video mode switching signal indicating the distant station to switch to a video mode of reception, said outgoing video-to-data mode switching signal and said outgoing data-to-video mode switching signal being further generated respectively in response to receipt of an incoming data mode identifier and an incoming video mode identifier from said distant station, respectively indicating the terminal station to switch to data and video modes of reception; LAPB (link access procedure balanced) control means for exchanging signals with said central processing unit; video coder/decoder means for generating an outgoing digital video signal and decoding an incoming digital video signal; multiplexer means for synchronously multiplexing said outgoing digital video signal from the video coder/decoder means with said outgoing data mode identifier to generate an outgoing composite video signal; demultiplexer means for synchronously demultiplexing an incoming composite video signal from said distant station into said incoming data mode identifier and a digital video signal, and supplying the demultiplexed video signal to said video coder/decoder means; an ISDN (integrated services digital network) interface for interfacing the terminal station with said integrated services digital signal network to which said distant station is also terminated; voice coder/decoder means connected to said ISDN interface for decoding an incoming voice digital signal from said distant station via said interface and transmitting an outgoing voice digital signal to said distant station via said interface, said interface multiplexing said outgoing voice digital signal with said outgoing composite video signal for transmission to said distant station and demultiplexing signals from said distant stations into said incoming voice digital signal and said incoming composite video signal; and switching means responsive to said outgoing video-to-data mode switching signal for coupling said LAPB control means to said ISDN interface for allowing said central processing unit to exchange said computer-generated data and said incoming and outgoing video mode identifiers with said distant station and to access said database, and responsive to said outgoing data-to-video mode switching signal for coupling said LAPB control means to said interface via said multiplexer and demultiplexer means for allowing said video coder/decoder means to exchange said outgoing and incoming composite video signals with said distant station, allowing said demultiplexer means to supply said incoming data mode identifier to said central processing unit via said LAPB control means and allowing said central processing unit to supply said outgoing data mode identifier to said multiplexer means via said LAPB control means.

Claim 10

A multimedia communications system as claimed in claim 7, wherein said central processing unit further generates an acknowledgment signal in response to receipt of said incoming data mode identifier from a distant station, and generates said video-to-data mode switching signal in response to receipt of said acknowledgment signal from a distant station.

Claim 11

A multimedia communications system as claimed in claim 7, wherein said central processing unit generates a dummy code containing a specified bit sequence during said video communication mode, said multiplexer means multiplexing said dummy code with said outgoing digital video signal during said video communication mode so that the dummy code occupies the same time slot position of the outgoing composite video signal as said outgoing data mode identifier.