Television conference telephone system

Claim 2

A television conference telephone system for conducting a conference between at least three subscribers comprising: at least three subscriber terminals, each subscriber terminal including means for transmitting and receiving audio signals and video signals and means operable by a subscriber for generating control signals indicating an intention to initiate a conference and for causing switching of video signals to those of a subscriber to speak; a telephone exchange including: means for coupling at least three of said subscriber terminals to the telephone exchange for conducting said conference; video signal distributing means; and means responsive to said control signals for selecting a particular one of said terminals for connection to the input of said video signal distributing means in accordance with a predetermined preferential order of the subscribers; said video signal distributing means being coupled to said selecting means to supply the video signal of said selected particular subscriber terminal to the video receiving means of all subscriber terminals involved in said conference, said video signal distributing means including an amplifier for receiving said video signal from said selected subscriber terminal, and an impedance converter connected to said amplifier and having a plurality of outputs coupled to a respective plurality of lines which in turn are coupled to a respective plurality of subscriber terminals, each of said outputs having a substantially constant output impedance matching the input impedances of the respective lines connected thereto regardless of the number of lines connected thereto, to prevent mismatch to the receiving terminals and to prevent loading of the input video signal.

Claim 3

A television conference telephone system according to claim 1 wherein: at each of said terminals, said transmitting and receiving means comprises means to transmit and receive an audio signal, and means to transmit a video signal and to receive and display a video signal; and said control signal generating means includes means for generating a signal indicating the intention of a subscriber to speak; said selecting means comprises: means to interconnect the audio signal lines of the subscribers involved in the conference in response to information transmitted from one of said subscriber terminals; and select control means connecting only one of said subscriber terminals to said video signal distributor among a plurality of subscRiber terminals which have transmitted signals indicating intention to speak; and said video signal distributing means supplying the video signal transmitted from said selected particular subscriber terminal to all of the subscriber terminals involved in said conference.

Claim 4

A television conference telephone system according to claim 2 wherein said select control means comprises: means responsive to said signals indicating intention to speak for generating an output pulse having a predetermined pulse width; a control switch means operated by said output pulse; and selector switch means corresponding to respective subscriber terminals and connected said control switch means, said selector switch means being operable in response to operation of said control switch means to connect only one of said subscriber terminals to said video signal distributor.

Claim 5

A television conference telephone system according to claim 3 wherein said select control means further comprises means to delay the pulse generated by said pulse generator means, and means responsive to the output pulse from said delay means to cause said pulse generator to stop generation of said pulse.

Claim 6

A television conference telephone system according to claim 3 wherein said control switch means and selector switches are comprised of relays.

Claim 7

A television conference telephone system according to claim 3 wherein said select control means includes means for preventing, for a predetermined period of time which is substantial as compared to the switching times involved, video signals from being switched into those of another subscriber by the video control signals of said another subscriber.

Claim 8

A television conference telephone system according to claim 2 wherein said means for generating a signal indicating intention to speak comprises a switch.

Claim 9

A television conference telephone system according to claim 1 wherein: at each of said terminals, said transmitting and receiving means comprises means to transmit and receive an audio signal, and means to transmit a video signal and to receive and display a video signal; and said control signal generating means includes means for generating a signal indicating the speech of a subscriber; said selecting means comprises: means to interconnect the audio signal lines of the subscriber involved in the conference in response to information transmitted from one of said subscribe terminals; and select control means connecting only one of said subscriber terminals to said video signal distributor among a plurality of subscriber terminals which have transmitted signals indicating speech; and said video signal distributing means supplying the video signal transmitted from said selected particular subscriber terminal to all of the subscriber terminals involved in said conference.

Claim 10

A telephone conference telephone system according to claim 8 wherein said means to transmit said signal indicating speech of a subscriber comprises an audio signal detector to detect the speech of a subscriber; an integrator to integrate the signal from said audio signal detector; a comparator to compare the output signal of said integrator with a reference signal; and a pilot signal generator operated by the output signal from said comparator.

Claim 11

A television conference telephone system for conducting a conference between at least three subscribers comprising: at least three subscriber terminals, each subscriber terminal including means for transmitting and receiving an audio signal, means for transmitting a video signal, and means to receive and display said video signal; a telephone exchange including: means for coupling at least three of said subscriber terminals to the telephone exchange for conducting said conference; video signal distributing means; select control means for selecting a particular one on said subscriber terminals for connection to the input of said video signal distributing means succeSsively at predetermined intervals and in accordance with a predetermined preferential order of the subscribers, said select control means comprising a plurality of switch means corresponding to respective subscriber terminals and means to control the operation of said switch means to select respective subscriber terminals; said video signal distributing means being coupled to said select control means to supply the video signal of a selected subscriber terminal to the video receiving means of all subscriber terminals involved in said conference, said video signal distributing means including an amplifier for receiving said video signal from said selected subscriber terminal, and an impedance converter connected to said amplifier and having a plurality of outputs coupled to a respective plurality of lines which in turn are coupled to a respective plurality of subscriber terminals, each of said outputs having a substantially constant output impedance matching the input impedances of the respective lines connected thereto regardless of the number of lines connected thereto, to prevent mismatch to the receiving terminals and to prevent loading of the input signal.

Claim 12

A television conference telephone system for conducting a conference between at least three subscribers comprising: at least three subscriber terminals, each subscriber terminal including means for transmitting and receiving an audio signal, means for transmitting a video signal, and means to receive and display said video signal; a telephone exchange including: means for coupling at least three of said subscriber terminals to the telephone exchange for conducting said conference; video signal distributing means; select control means for selecting a particular one on said subscriber terminals for connection to the input of said video signal distributing means succeSsively at predetermined intervals and in accordance with a predetermined preferential order of the subscribers, said select control means comprising a plurality of switch means corresponding to respective subscriber terminals and means to control the operation of said switch means to select respective subscriber terminals; said video signal distributing means being coupled to said select control means to supply the video signal of a selected subscriber terminal to the video receiving means of all subscriber terminals involved in said conference, said video signal distributing means including an amplifier for receiving said video signal from said selected subscriber terminal, and an impedance converter connected to said amplifier and having a plurality of outputs coupled to a respective plurality of lines which in turn are coupled to a respective plurality of subscriber terminals, each of said outputs having a substantially constant output impedance matching the input impedances of the respective lines connected thereto regardless of the number of lines connected thereto, to prevent mismatch to the receiving terminals and to prevent loading of the input signal.

Claim 13

A television conference telephone system according to claim 10 wherein said means to control the operation of said switch means includes a plurality of flip-flop circuits corresponding to respective terminals for controlling said switch means, and a clock pulse generator connected to said flip-flop circuits for generating a clock pulse at predetermined time intervals to reset successively said flip-flop circuits.

Claim 14

A television conference telephone system according to claim 10 wherein each one of said terminals further includes means for generating a signal indicating the speech of the subscriber and wherein said select control means includes means to enable one of said switch means responsive to said speech indicating signal.