Selective blanking of video display

Claim 2

In a video display system wherein intermixed synchronizing pulses and video signals flow from a central unit to a plurality of display monitors, each of which contains its own display tube, said signals being supplied from a plurality of sources, whereby, in the absence of selective blanking, each tube displays information from said plurality of sources in a corresponding plurality of vertically displaced display areas in a single display field: a first device located at said central unit for combining a blanking impulse with that synchronization pulse in the synchronizing pulse train which immediately precedes the information for display from any selected source whereby a composite pulse train is supplied to all monitors, said device including a. first means to produce said synchronizing pulse train, b. second means to produce control pulses a preselected intervals, each such interval having at least a portion thereof in time coincidence with a portion of the period in which a pulse is produced in the synchronizing train, c. third means to produce a blanking impulse whenever a timing signal is received thereby during the time of a control pulse produced by the second means, and d. fourth means to combine said pulse train with said impulse to produce said composite pulse train; and a second device disposed at each monitor and responsive to said composite train to detect the presence of said blanking impulse and thereafter to blank the display on the corresponding tube of the information from the selected source, said second device being manually enabled and disabled, said second deviCe including a. first means for deriving control signals from the detected impulses, and b. second means responsive to said control signals to blank the display by interrupting the flow of video information to the tube during the blanking step.

Claim 3

In a video display system wherein intermixed synchronizing pulses and video signals flow from a central unit to a plurality of display monitors, said video signals being supplied sequentially from a plurality of sources, apparatus for blanking individual monitors from displaying the video signals from selected ones of said sources comprising: means located at said central unit for generating a composite pulse train, said pulse train including a plurality of synchronizing pulses separated by a predetermined time interval, each synchronizing pulse having a predetermined time duration and selected ones of said synchronizing pulses including a timing pulse within the predetermined time duration of said selected ones of said synchronizing pulses, said timing pulse indicating the start of video signals from one of the plurality of sources and being represented by a change in signal level within said selected ones of said synchronizing pulses; an input terminal associated with each of said plurality of display monitors; means coupled to said input terminal and including a control terminal for passing the video signals from said central unit for further processing in the absence of a blanking signal at said control terminal; and means having an input connection coupled to said input terminal and an output connection coupled to said control terminal for generating selective blanking signals in response to the timing pulses of said composite pulse train.

Claim 4

In a video display system wherein intermixed synchronizing pulses and video signals flow from a central unit to a plurality of display monitors, said video signals being supplied sequentially from a plurality of sources, apparatus for blanking individual monitors from displaying the video signals from selected ones of said sources comprising: means located at said central unit for generating a composite pulse train, said pulse train including a plurality of synchronizing pulses separated by a predetermined time interval, each synchronizing pulse having a predetermined time duration and selected ones of said synchronizing pulses including a timing pulse within the predetermined time duration of said selected ones of said synchronizing pulses, said timing pulse indicating the start of video signals from one of the plurality of sources and being represented by a change in signal level within said selected ones of said synchronizing pulses; an input terminal associated with each of said plurality of display monitors; means coupled to said input terminal and including a control terminal for passing the video signals from said central unit for further processing in the absence of a blanking signal at said control terminal; and means having an input connection coupled to said input terminal and an output connection coupled to said control terminal for generating selective blanking signals in response to the timing pulses of said composite pulse train.

Claim 5

A video display system according to claim 2 wherein said means for passing the video signals is a normally open gate having a control element coupled to said means for generating selective blanking pulses and being operative in response to blanking pulses to close said normally open gate.

Claim 6

A video display system according to claim 2 wherein said means for generating selected blanking pulses comprises: first gating means having a first input connection coupled to said input terminal, a second input connection and an output connection, and being operative in response to corresponding signal levels at its first and second input connections to change the output signal level at its output connection from a first level to a second level; multivibrator means having an input connection coupled to the output connection of said first gating means and an output connection coupled to the second input connection of said first gating means and being operative in response to a change in the first gating output signal from the second level to the first level to produce a pulse at its output connection; second gating means having a first input connection connected to the output connection of said multivibrator means and a second input connection connected to the first input connection of said first gating means and an output connection and being operative in response to the composite pulse train signal and the multivibrator output signal being at said second signal level to generate an output signal at the output connection of said gating means whereby the second gating means only produces an output signal when there is a change in signal level within said synchronizing signal; means coupled to the output connection of said second gating means for generating a plurality of blanking pulses in response to an output signal from said second gating means; and means for selectively connecting certain ones of said blanking pulses to the control terminal of said means for passing the video signals whereby video signals are selectively blanked from the associated display when blanking pulses are present at the control terminal of said means for passing.