A communications link for coupling a computer to a distantly located monitor and keyboard, comprising:
- a first signal conditioning circuit coupled to video output terminals of said computer, said terminals conveying horizontal sync signal HS and vertical sync signal VS, primary R, G and B, and secondary r, g, and b video signals, and further coupled to a keyboard clock terminal and a keyboard data terminal conveying keyboard data signals to said computer, said first signal conditioning circuit also coupled to stable potentials including power and ground potentials, said first signal conditioning circuit disposed for conditioning said keyboard signals and providing conditioned said keyboard signals to said computer, and further providing conditioned said VS and HS, conditioned said primary R, G, and B, and conditioned said secondary r, g, and b video signals to said monitor, said first signal conditioning circuit comprising:
- a plurality of discrete, TTL amplification means, one of each coupled to said video output terminals for providing TTL level signals HS and VS and TTL level primary and secondary video signals,
- a plurality of discrete amplitude attenuation means, one of each coupled to one of each said TTL amplification means coupled to said primary and said secondary video signals, for reducing amplitude of said TTL level primary and secondary video signals to a predetermined level,
- a plurality of discrete biasing means, one of each coupled to one of each said amplitude attenuation means, for biasing a center voltage of the amplitude attenuated primary and secondary video signals to a predetermined potential,
- a first capacitor coupled between said keyboard clock terminal and a stable potential of said stable potentials for shunting frequencies on said clock terminal significantly higher than a clock pulse frequency to said stable potential, and
- a second capacitor coupled between said keyboard data terminal and said stable potential for shunting frequencies on said data terminal of a significantly higher frequency than a data frequency to said stable potential;
- an extended-in-length cable having a plurality of discrete, insulated conductors coupled at one end to said first signal conditioning circuit and disposed for conveying said keyboard signals and said stable potentials and biased and amplitude attenuated said primary and secondary video signals and said TTL level signals HS and VS;
- and
- a second signal conditioning circuit coupled to an opposite end of said conductors of said cable and disposed for reconstructing said video signals and providing further conditioned said video signals to said monitor and receiving said keyboard signals from said keyboard and providing said keyboard signals to conductors of said cable, said second signal conditioning circuit comprising:
- a plurality of discrete threshold circuit means responsive to said video signals, one of each coupled to discrete said conductors of said cable conveying said primary and secondary video signals, for reshaping said video signals degraded by said conductors of said cable and providing TTL level, reshaped said video signals to said monitor,
- a plurality of relatively short conductors coupled at one end to output terminals of said keyboard conveying said keyboard signals and to power terminals of said keyboard, said short conductors coupled at an opposite end to respective said conductors of said cable, for providing said keyboard signals to said conductors of said cable and said stable potentials to said keyboard,
- a first resistor coupled between a said short conductor conveying said clock signal and a said short conductor conveying stable potential, and
- a second resistor coupled between a said short conductor conveying said data signal and a said short conductor conveying said stable potential, said first and second resistors disposed for decreasing rise times of said clock and data signals,
- whereby said keyboard signals are applied to said conductors of said cable via said short conductors of said second signal conditioning circuitry, said keyboard signals being received and conditioned by said first signal conditioning circuitry and thereafter provided to said computer, while said video signals and said stable potentials are provided by said computer to said first signal conditioning circuitry, conditioned therein, and applied to said discrete conductors of said cable to said second signal conditioning circuitry where said video signals are reshaped and provided to said monitor, and said potentials are provided to said keyboard.