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Institutional audio-visual system including a plural operating mode television receiver

  • US 4,319,277 A
  • Filed: 07/02/1980
  • Issued: 03/09/1982
  • Est. Priority Date: 07/02/1980
  • Status: Expired due to Term
First Claim
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1. An institutional television system including a television receiver and a source of a plurality of modulated RF carrier signals occupying respectively different spectrum channels, with at least one of said channels occupied by modulated RF carrier signals of a first type conveying television picture information with accompanying sound information and inclusive of a picture carrier modulated by composite video signals inclusive of a video sync component occurring during synchronizing intervals also including a blanking level representative of image brightness, and another of said channels occupied by modulated RF carrier signals of a second type conveying sound information to the exclusion of television picture information and inclusive of a picture carrier devoid of video signal modulation;

  • said television receiver including;

    adjustable input means, coupled to said source, for selectably rendering said television receiver responsive to a selected one of said channels and for developing a first output representative of the sound information conveyed by said selected channel and a second output representative of the video signal modulation, if any, of the picture carrier of said selected channel;

    a sound reproducer;

    means for rendering said sound reproducer responsive to said first output;

    an image display device;

    video signal processing means similarly energized for each channel selection condition of said adjustable input means and having an input responsive to said second output of said adjustable input means and an output coupled to said image display device for controlling the light output thereof;

    a sync separator responsive to said second output of said adjustable input means for developing a separated sync component only when the selected channel is occupied by modulated RF carrier signals of said first type; and

    means for controlling the operation of said video signal processing means in accordance with the output of said sync separator such that (1) the light output of said image display device is controlled in accordance with said video signal modulation when the output of said sync separator indicates that the selected channel is occupied by modulated RF carrier signals of said first type, and (2) the light output of said image display device is inhibited when the output of said sync separator indicates that the selected channel is occupied by modulated RF carrier signals of said second type;

    wherein said controlling means comprises;

    means for deriving periodic keying signals from said video sync component of said composite video signal such that said keying signals are interrupted in the absence of said video sync component;

    keyed control means normally operative in response to said keying signals, for providing an output signal normally corresponding to an image brightness control signal;

    means for coupling said output signal of said keyed control means to said video signal processing means for normally controlling the blanking level of video signals processed thereby and accordingly controlling the brightness of an image reproduced by said image display device; and

    whereinsaid keyed control means is disabled when said keying signals are interrupted in the absence of said video sync component such that said output signal of said keyed control means exhibits a magnitude and sense sufficient to blank output signals from said video signal processing means for inhibiting the light output of said image display device.

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