VGA signal converter for converting VGA color signals to VGA monochrome signals

A conversion system for converting analog VGA color signals to gray scale monochrome signals comprising:

• a source of color analog VGA video signals, including R, G, and B signals, each having varying amplitude and a maximum amplitude of about 700 millivolts, one of each said R, G, and B signals being applied to a respective R signal conductor, a G signal conductor, and a B signal conductor;
• a load impedance coupled between each of said signal conductors and a reference potential, for emulating an electrical load of a VGA color monitor;
• first, second, and third signal buffers, each having an input coupled to a respective one of said signal conductors, and an output terminal responsive to a respective one of said R, G, and B signals for providing on each said output terminal a respective signal voltage;
• first, second, and third current limiting means, one of each being coupled to one of each said output terminal of respective ones of said first, second, and third signal buffers for limiting each said current flow from each said voltage potential;
• and
• a common junction responsive to said first, second, and third current limiters for additionally combining each limited said current flow to develop an analog monochrome VGA video signal potential having an optimum level of contrast between each of the R, G, and B signals and all mixtures thereof.

A conversion system for coupling analog color VGA signals to either an analog monochrome VGA monitor or analog color VGA monitor comprising:

• a source of analog color VGA video signals providing at least R, G, and B video signals on respective R, G, and B signal conductors;
• a current source;
• first, second, and third current modulators, each having an input coupled to a respective one of said R, G, and B signal conductors, a terminal coupled to said current source, and an output terminal, for providing modulated R, G, and B signals on one of each respective said output terminals;
• a plurality of first signal paths, one of each being coupled to one of each said output terminals, and each further comprising:
• a unidirectional current alternator for limiting a signal current flow of each of said current modulated R, G, and B signals to limited, discretely differing R, G, and B signal current flows, and
• a common junction coupled to each said current attenuator, for additively combining said reduced R, G, and B currents, developing an analog monochrome VGA video signal potential having a different shade of gray for each said R, G, and B video signals and all mixtures thereof, and providing on a discrete signal conductor said monochrome video signal as a first output;
• and
• a plurality of second signal paths, one of each being coupled to one of each said output terminals of said first, second, and third current modulators, each of said second signal paths being operative in mutually exclusive relation with each of said plurality of first signal paths, for providing as a second output said current modulated R, G, and B signals.

An extended VGA communications link for coupling at least analog VGA video signals R, G, and B from R, G, and B video terminals of a computer to an analog VGA monitor comprising:

• a shielded insulated cable and having at least three discrete insulated conductors, each said conductor having a first end and a second end;
• a bias source coupled to each said second end of said three conductors, for providing a DC bias to each said second end of said three conductors;
• a plurality of modulators, each having a current input, and each being responsive to a respective one of the R, G, and B signals, one of each said current input being coupled to a said first end of a respective one of said three conductors, for powering each said modulator by said bias source through a respective said conductor and providing a modulated R, G, and B signal current flow through each of said conductors;
• a plurality of amplifiers, each having an input coupled to a respective said second end of said conductors and being responsive to a respective said signal current flow, and each having an output terminal, for providing R, G, and B signal outputs on said output terminals;
• a plurality of first signal paths, one of each being coupled to one of each of said output terminals, each said first path including:
• unidirectional current limiter means for reducing a signal current flow of each said R, G, and B outputs to discretely differing current flows, and
• an additively combining junction couplable to a monochrome VGA monitor, for additively combining said discretely differing current flows to develop an analog monochrome VGA signal having an optimum contrast between various shades of gray;
• and
• a plurality of second signal paths couplable to a color VGA monitor, one of each being coupled to one of each said output terminal of respective ones of said plurality of current amplifiers, and being operative in mutually exclusive relation with said plurality of first signal paths;
• whereby said gray scale VGA signal is provided to an analog VGA monochrome monitor remotely located from said computer, or said current amplified R, G, and B signals are provided to an analog VGA color monitor remotely located from said computer.

A communications link for coupling video output terminals of an analog VGA video source from a computer and conveying at least analog VGA R, G, and B signals to a first analog VGA monitor located generally proximate said video source and to a second VGA analog monitor remotely located from said video source comprising:

• a bias source from said computer;
• a plurality of first current modulators, each being coupled to a bias source, and each having first output terminals and being responsive to said R, G, and B signals, for providing a first set of current modulated said R, G, and B signals, and a plurality of second current modulators each being coupled to said bias source, and each having second output terminals and being responsive to said R, G, and B signals, for providing a second set of current modulated said R, G, and B signals;
• a plurality of first signal paths couplable to said first monitor where said first monitor is a VGA monochrome monitor, one of each being coupled to one of each said first output terminals, and each further comprising:
• a unidirectional current attenuator for reducing a signal current flow of each of said current modulated R, G, and B signals to a discretely different, reduced current flow, and
• a common junction coupled to each of said current attenuators, for combining each said reduced current flow, and developing an analog monochrome VGA video signal having an optimum shade of gray for each said R, G, and B signal and all mixtures thereof;
• a plurality of second signal paths couplable to said first monitor where said first monitor is a VGA color monitor, one of each being coupled to one of each said second output terminals and being operative in mutually exclusive relation with said first signal paths, for providing said current modulated R, G, and B signals to said VGA color monitor;
• a shielded, insulated cable having at least three discrete, insulated conductors, each said conductor having a first end and a second end;
• said bias source being coupled to each said second end of said three conductors, for providing a DC bias to each of said three conductors, and each said first end being coupled to a respective one of said second output terminals, and powering said second current modulators through a respective said conductor, for providing current modulated said R, G, and B signals through each of said conductors;
• a plurality of current amplifiers each having an input coupled to one of each of said second ends of said conductors and responsive to one of each said second set of said modulated R, G, and B signals and each having a third output terminal, for providing amplified R, G, and B signal outputs on said third output terminals;
• a plurality of third signal paths, one of each being coupled to one of each of said third output terminals, and each further comprising:
• a second unidirectional current attenuator for reducing a signal current flow of each of said amplified R, G, and B signals to a discretely different, reduced current flow, and,
• a second common junction coupled to each said second current attenuators, for combining each said reduced signal current flow, developing a second analog monochrome VGA video signal having a different shade of gray for each said R, G, and B signal and mixtures thereof, and being couplable to said second monitor where said second monitor is a VGA monochrome monitor;
• and
• a plurality of fourth signal paths, each being coupled to a respective one of said third output terminals, and being operative in mutually exclusive relation with said third signal paths, for providing said amplified R, G, and B signals to said second monitor where said second monitor is a VGA color monitor.